Research on the Damage Mechanism and Reservoir Protection Drilling Fluid System of Jurassic Reservoir in Zhenbei Oilfield

Research on the Damage Mechanism and Reservoir Protection Drilling Fluid System of Jurassic Reservoir in Zhenbei Oilfield | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Research on the Damage Mechanism and Reservoir Protection Drilling Fluid System of Jurassic Reservoir in Zhenbei Oilfield Jingguang Wang, Wang He, Min Zhang, Chen He, Peiming Shi This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6426437/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 02 Feb, 2026 Read the published version in Scientific Reports → Version 1 posted 11 You are reading this latest preprint version Abstract Low permeability oil and gas reservoirs have become increasingly prominent in China's oil and gas exploration and development and are an important area for reserve growth, and the Yanchang formation in the Ordos Basin is a low-permeability reservoir that contains abundant oil and gas resources. Jurassic reservoirs are widely distributed in the Ordos Basin, and the proportion of reservoir production has been increasing year by year. In this study, the mechanism of drilling fluid damage in Jurassic reservoirs was revealed through the analysis of physical parameters, rock characteristics, pore structure, and sensitivity. As a result, the reservoir properties are mainly intergranular pores and dissolution pores, with low displacement pressure, low porosity, and high permeability, and the overall physical properties are good. When foreign solid and liquid phases invade, it is easy to cause throat particle migration, leading to pore blockage and serious reservoir damage. Secondly, through the optimization of oil soluble temporary plugging agents and filter loss reducing agents, combined with experimental methods such as particle size analysis and scanning electron microscopy, a drilling fluid system for Jurassic reservoir protection in Zhenbei Oilfield was obtained, which includes temporary plugging agent G325 and self-degradable filter loss reducing agent. The medium pressure water loss of the drilling fluid system is 4.5 mL, with an average sealing rate of 71.06% and an average core permeability recovery rate of 97.80%. overall, the drilling fluid has excellent sealing performance and reservoir protection performance. Physical sciences/Energy science and technology Physical sciences/Materials science Oil and gas exploration and development Low permeability oil and gas reservoirs Reservoir damage mechanism Drilling fluid system Reservoir protection performance Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 1. Introduction The status of low-permeability oil and gas reservoirs in China's oil and gas exploration and development has become increasingly prominent and represents a crucial area for reserve augmentation. The Yanchang Formation within the Ordos Basin harbors abundant oil and gas resources within its low-permeability reservoirs [ 1 ] . Zhenbei Oilfield, located in the Longdong region of Gansu Province, is structurally positioned in the southwestern portion of the Yishan Slope in the Ordos Basin. The oil exploration activities in Zhenbei Oilfield initiated in the 1970s, and industrial oil flows have been achieved in formations such as Chang 3 and Chang 8, thereby exhibiting substantial exploration potential. In recent years, the practice of oil and gas exploration and development has substantiated that Zhenbei Oilfield is among the principal oil and gas enrichment zones. It has been ascertained that the reservoir physical properties of formations like Chang 3 are favorable, and the production from oil testing and trial production is relatively high, indicating a promising outlook for reserve increment and production enhancement [ 2 ] . The ancient geomorphology in the Zhenbei area predominantly comprises highlands, slopes, river valleys, and tributary gullies. Jurassic reservoirs are chiefly distributed on the slopes and slope mouths flanking the Zhenbei tributary river and the Yanwu tributary river. Jurassic reservoirs are widely dispersed across the basin. The reservoir physical properties are mainly manifested as intergranular pores and dissolution pores, with a relatively low displacement pressure, low porosity yet high permeability, and an overall satisfactory physical property profile. When external solid and liquid phases intrude, it is prone to trigger the migration of throat particles, leading to pore clogging and significant reservoir damage [ 3 – 5 ] . The Fuxian Formation and the Yan 10-Yan 8 oil-bearing formations within the Jurassic strata in the Longdong area of the Ordos Basin constitute the primary oil-producing layers in this region. In comparison with the Yanchang Formation reservoirs, the Jurassic reservoirs possess the advantages of lower development costs and better comprehensive benefits [ 6 ] . In the Changqing Oilfield, the production proportion of Jurassic reservoirs has been progressively increasing year by year. In 2022, the proportion of annual production construction scale exceeded 30%, and it has emerged as a key stratum for the oilfield company to augment reserves and boost production, playing a vital role in the oilfield's production augmentation and stable production. In the process of oil and gas resource exploration and development of Jurassic reservoirs, the design and research and development of reservoir protection drilling fluid systems are the linchpins for ensuring the release of oil and gas production capacity [ 7 ] . The evolution of drilling fluid systems has traversed from the initial clear water and polymer drilling fluids to the more prevalently applied sulfonated drilling fluids and oil-based drilling fluids, as well as the environmentally friendly drilling fluid systems developed to meet the corresponding environmental protection and long-term development requisites [ 8 ] . Oil and gas reservoir protection is a comprehensive and systematic project, and the design and optimization of drilling fluid systems are of paramount importance. The principal reservoir protection drilling fluid technologies encompass positive colloid drilling fluids, synthetic-based drilling fluids, formate drilling fluids, and polyalcohol drilling fluids, among others [ 9 ] . However, these drilling fluids are less commonly utilized in Jurassic reservoirs. Jia Shengguo addressed the technical conundrums of the low-porosity and low-permeability reservoirs in the Toutunhe Formation of the Jurassic in the Fudong Slope area, where the shale content in the reservoir rocks is elevated, hydration expansion is liable to occur, thereby inducing complex downhole conditions and posing difficulties in reservoir protection. Through comprehensive reservoir sensitivity prediction and diverse sensitivity evaluations, he proposed improvement strategies for the formulation design and optimization of the reservoir protection drilling fluid system for on-site construction, with a particular emphasis on fortifying its inhibition and plugging capabilities. The permeability recovery value of reservoir core dynamic pollution damage can reach 83% [ 10 ] . Zhang Rui et al. took the Chang 8 reservoir in the Wuqi area of the Ordos Basin as the research target and developed a suite of reservoir protection measures for safeguarding the Wuqi Oilfield. Specifically, temporary plugging agents SLD-1 and EL-1 that match the reservoir pores and pore throat structures, as well as oil layer protection agents TYZ-7 and JYP were selected [ 11 ] . Dong Hongwei et al. confronted the current situation where the physical properties of the Yan'an Formation in certain blocks of the Longdong Oilfield are favorable, yet the production is relatively low. The root cause was identified as the inability of the drilling fluid system during drilling operations to achieve reservoir protection. Subsequently, in combination with the oil layer protection agent PWTBA - Ⅱ, a novel reservoir protection drilling fluid technology was developed, reducing the damage rate to the oil and gas reservoir to 10.61% [ 12 ] . In summary, it is evident that the design and optimization of oil and gas reservoir protection drilling fluid systems are primarily accomplished through reservoir sensitivity prediction and sensitivity evaluation, along with the reinforcement of the plugging performance, filtration loss performance, anti-collapse performance of the drilling fluid systems. In light of the foregoing, this study, in alignment with the reserve augmentation and production escalation imperatives of the oilfield enterprise and leveraging the production superiority of Jurassic reservoirs, undertakes an evaluation of the diverse sensitivities exhibited by Jurassic reservoirs within the Ordos Basin. Thereby, the damage mechanism inherent in the Jurassic reservoirs of Zhenbei Oilfield is unveiled. Concurrently, investigations and trials pertaining to the drilling fluid technology for safeguarding Jurassic reservoirs are conducted, with the overarching objective of attenuating reservoir impairment and augmenting the efficacy of oilfield exploitation. 2. Experiment 2.1 Materials 2.1.1 Chemical reagents The rock samples of Jurassic reservoirs, together with the plugging agents G325 and GN362 utilized in drilling fluids, ultra-fine calcium carbonate (CaCO 3 ), self-degradable fluid loss additives, fluid loss additive NFA-25, fluid loss additive ASP-1250, and bentonite, were all furnished by the oil production plants or the Engineering Technology Management Department of Changqing Oilfield. Meanwhile, the analytical reagent-grade chemicals such as sodium carbonate and sodium hydroxide were procured from Chengdu Kelong Chemicals Co., Ltd. 2.1.2 Others DYG-II multifunctional core displacement experimental device, AutoPore9600/9510 high-performance fully automatic mercury intrusion porosimeter, FlexSEM1000 compact intelligent scanning electron microscope, X Pert PRO MPD X-ray diffractometer, Master sizer 2000 laser particle size analyzer, PPA plugging tester, etc. 2.2 Experimental Method The physical property parameters, mineral composition, and pore structure of the Jurassic reservoir rock samples were all determined in accordance with the existing conventional experimental methods. The reservoir sensitivity evaluation was carried out referring to the industry standard SY/T 5358 − 2010 "Evaluation Method of Reservoir Sensitivity Flow Experiment". The performance evaluation of the reservoir protection drilling fluid system was implemented with reference to GB/T 29170 − 2012 "Petroleum and Natural Gas Industry-Laboratory Testing of Drilling Fluids". 3. Results and Discussion 3.1 Damage Mechanism of Jurassic Reservoirs 3.1.1 Reservoir physical property parameters The reservoir physical property parameters of the Jurassic reservoirs (including Yan 4, Yan 5, Yan 6, Yan 7, Yan 8, Yan 9 and Yan 10) in the No. 11 Oil Production Plant and the Jurassic reservoirs (Yan 8, Yan 9 and Yan 10) in the No. 2 Oil Production Plant were studied. The experimental results are shown in Table 1 below. The research results indicated that the average porosity of the Jurassic reservoirs in the No. 11 Oil Production Plant is 14.4%, and that of the Jurassic reservoirs in the No. 2 Oil Production Plant is 16.0%. In addition, the average permeability of the Jurassic reservoirs in the No. 11 Oil Production Plant is 183.9×10⁻³ µm², and the average permeability of the No. 2 Oil Production Plant is 133.1×10⁻³ µ m². Based on the comprehensive porosity and permeability data, it can be seen that the Jurassic reservoirs are all low-porosity and medium-permeability reservoirs, which are more prone to damage caused by blockage of external solid particles [ 13 – 16 ] . Table 1 Physical properties parameters of Jurassic reservoirs Oil Production Plant Horizon Number of samples Porosity(%) Permeability(mD) Area Average value Minimum value Maximum value Average value Minimum value Maximum value The 11th Oil Production Plant Yan 4 + 5 280 16.2 4.9 24.0 408.7 0.4 914.5 Yan 6 312 14.7 2.3 22.1 153.3 0.3 430.2 Yan 7 270 14.5 1.4 22.7 184.5 0.7 553.6 Yan 8 932 14.5 1.0 21.6 304.5 0.6 927.4 Yan 9 775 13.3 0.5 19.8 48.8 0.5 172.5 Yan 10 128 13.0 0.7 25.0 3.8 0.2 165.7 The 2nd Oil Production Plant Yan 8 22 15.4 10.0 17.0 77.7 1.1 520.0 Yan 9 256 16.4 8.8 23.5 207.9 1.1 2730.0 Yan 10 353 16.2 10.1 19.9 113.6 1.2 3961.9 3.1.2 Characteristics of reservoir rocks The research on reservoir characteristics serves as the fundamental basis for a series of crucial aspects in the field of oil and gas, including reservoir evaluation and prediction, as well as oilfield development and program readjustment. In-depth analyses and investigations were specifically conducted on the clastic component contents and interstitial material contents within the Jurassic reservoirs of Zhenbei Oilfield. The corresponding experimental outcomes are presented in Tables 2 and 3 , along with Fig. 1 . Table 2 Statistical table of clastic composition content of Jurassic reservoir in Zhenbei Oilfield Horizon Number of samples Clastic composition (%) The Others (%) Lump Quartz Group Feldspar Group Total Cuttings Igneous Rock Cuttings Metamorphic Rock Cuttings Sedimentary Rock Cuttings Yan 4 + 5 13 62.3 18.1 14.6 1.3 12.3 1.0 5 Yan 6 14 55.6 17 19.7 1.5 17.2 1.0 7.7 Yan 7 15 55.7 13.5 19.9 1.4 16.5 2.0 10.9 Yan 8 48 54.9 14.7 16.6 1.2 14.4 1.0 13.8 Yan 9 55 54.2 14.9 18.6 1.3 15.3 2.0 12.3 Yan 10 57 50.7 8.7 21.2 1.7 11.2 8.3 19.3 Table 3 Statistical table of interstitial material content of Jurassic reservoir in Zhenbei Oilfield Horizon Number of samples Clastic composition (%) Total (%) Lump Kaolinite Hydromica Chlorite Calcite Ferrocalcite Siliceous Dolomite Yan 4 + 5 16 1.2 1.5 1.2 0.9 1.1 1.2 1.2 8.3 Yan 6 14 0.8 1.3 1.7 1.6 1.9 1.5 0.5 9.2 Yan 7 15 1.8 2.5 0.5 0.7 1.0 2.1 2.1 10.6 Yan 8 45 1.6 2.5 1.3 2.2 1.6 1.8 0.7 11.7 Yan 9 55 2.4 2.8 0.2 2.1 1.8 1.5 1.5 12.2 Yan 10 57 2.5 4.3 0.3 1.8 0.4 3.9 0.1 13.1 Figure 1 , Tables 2 and 3 , conspicuously revealed the predominant lithology of the Jurassic reservoirs within Zhenbei Oilfield is medium-to-fine grained quartz and feldspar lithic sandstones, with a proportion ranging from 59.4 to 80.4%. The interstitial substances are principally constituted by hydromica, silica, and kaolinite. Notably, kaolinite exhibits a rather feeble resistance to mechanical forces, and the interlayer bonding within its crystal structure is tenuous. When subjected to the impingement of high-velocity fluid flows, it undergoes dissociation, cleavage, and dispersion, thereby generating flaky microparticles. This phenomenon leads to the dispersion and migration of solid phases [ 17 – 19 ] , subsequently diminishing the reservoir permeability and ultimately inflicting damage upon the Jurassic reservoirs of Zhenbei Oilfield. 3.1.3 Reservoir pore structure The study of reservoir pore structure characteristics has become a crucial part in reservoir characteristic research and is closely related to reservoir evaluation and oil and gas productivity prediction. During this research, a quantitative analysis was carried out on the pore types, pore throat sizes, etc. of Zhenbei Oilfield, such as porosity, permeability, intergranular pores, intercrystalline pores, etc. The specific details are shown in Table 4 below, and the mercury injection curve of the Jurassic reservoir in Zhenbei Oilfield is shown in Fig. 2 . Table 4 Pore structure characteristics of Jurassic reservoirs in Zhenbei Oilfield Horizon Area Porosity (%) Permeability Intergranular pore Intercrystalline pore Microcrack Dissolution pore Pore - area percentage (%) Intergranular dissolution pores Feldspar dissolution pores Cuttings dissolution pores Matrix dissolution pores Minor total Yan 4 + 5 280 16.2 408.7 9.5 0.2 0.0 0.3 1.6 1.0 0.0 2.8 12.5 Yan 6 312 14.7 153.3 6.2 0.3 0.0 0.4 1.2 0.4 0.0 2.0 8.5 Yan 7 270 14.5 184.5 5.5 0.4 0.0 0.5 1.0 0.4 0.0 1.9 7.8 Yan 8 932 14.5 304.5 7.6 0.3 0.0 1.3 0.6 0.5 0.2 2.7 10.5 Yan 9 775 13.3 48.8 8.5 0.3 0.0 1.1 0.9 0.5 0.0 2.5 11.2 Yan 10 128 13.0 3.8 8.6 0.8 0.3 0.7 0.8 0.6 0.0 2.2 11.8 The pore structure characteristics and mercury injection curves of the Jurassic reservoirs in Zhenbei Oilfield are exhibited as presented above. The porosity values are situated within the range of 13.0 to 16.2%. Notably, a substantial disparity in permeability is observed among different stratigraphic horizons. The mean value of planar porosity amounts to 10.4%, and in specific localized regions, it can ascend above 11%. Furthermore, as depicted in Table 4 , the pore types of the Jurassic reservoirs are predominantly intergranular pores and dissolution pores. The intergranular pores manifest in diverse forms such as triangular, polygonal, and irregular shapes. The dissolution pores are frequently elongated or assume a harbor-like morphology, and the connectivity of pore throats exhibits significant variability. These two types of pores both exert a favorable influence on enhancing the porosity and permeability of the reservoirs [ 20 ] . Consequently, the overall physical properties of the Jurassic reservoirs in Zhenbei Oilfield are relatively favorable. In addition, the mercury injection curves disclose that the displacement pressure is comparatively low, thereby facilitating the backflow treatment process. 3.1.4 Reservoir Sensitivity Evaluation Under laboratory conditions, a series of in-depth studies were meticulously carried out to assess the sensitivity of the Jurassic reservoirs in Zhenbei Oilfield, with a particular focus on velocity sensitivity, water sensitivity, alkali sensitivity, and acid sensitivity [ 21 – 23 ] . The experimental results are detailed in Table 5 provided hereinafter. In strict accordance with industry standards and by meticulously analyzing the evaluation indices for velocity sensitivity, water sensitivity, alkali sensitivity, and acid sensitivity, it has been ascertained that the velocity sensitivity damage of the Jurassic reservoirs in Zhenbei Oilfield is of a moderately weak nature. Similarly, the water sensitivity damage also demonstrates a moderately weak propensity, with an average damage rate recorded at 31.33%. When the pH value attains 14, the average damage rate is measured as 40.77%, which is designated as moderately weak damage. At a pH value of 10, the average damage rate is 15.46%, signifying a weak alkali sensitivity. Moreover, the acid sensitivity of the Jurassic reservoirs is classified as weak acid sensitivity. Based on the comprehensive and detailed evaluations of velocity sensitivity, water sensitivity, alkali sensitivity, and acid sensitivity, the hierarchical order of the severity of sensitivity of the Jurassic reservoirs is conclusively determined as follows: velocity sensitivity > water sensitivity > alkali sensitivity > acid sensitivity. Based on the analyses of the physical properties, rock characteristics, pore structure, and sensitivity of the Jurassic reservoirs in Zhenbei Oilfield, it can be concluded that the Jurassic reservoirs are low-porosity and medium-permeability oil reservoirs. The intrusion of external solid and liquid phases into the formation is prone to causing reservoir damage. Moreover, the rock characteristics are mainly dominated by quartz and feldspar, and the interstitial materials are primarily composed of kaolinite. Kaolinite has relatively weak resistance to mechanical forces, and the connection between crystal layers is tenuous. Under the impact of high-velocity fluids, it will lead to dissociation, splitting, and dispersion to form flaky particles, resulting in dispersion and migration, which will reduce the reservoir permeability and also easily cause reservoir damage. In addition, the velocity sensitivity and water sensitivity of the reservoirs are relatively prominent, which can cause the hydration expansion, dispersion, and migration of particles in the reservoir, and block the pore throats, thereby leading to a decline in the reservoir permeability [ 24 – 25 ] . 3.2 Jurassic Reservoir Protection Drilling Fluid 3.2.1 Construction of Reservoir Protection Drilling Fluid System In order to avert the infiltration of external solid and liquid phases into the formation and the damage resulting from particle migration within the reservoir due to velocity sensitivity, a highly efficient drilling fluid technology characterized by robust plugging capabilities, low fluid loss, and oil solubility has been formulated during the research process. The overarching objective is to enable the gradual dissolution and self-degradation of the drilling fluid as the development progresses in the later stages, thereby reinstating the unobstructed state of pore throats and accomplishing the goal of reservoir protection. The crucial aspects in the R & D of this drilling fluid technology are twofold. Firstly, it entails the meticulous selection of temporary plugging agents that are precisely commensurate with the pore dimensions of the Jurassic reservoirs. Secondly, it involves the painstaking research and identification of appropriate self-degrading fluid loss additives, with the aim of curtailing the invasion of external fluids. On the one hand, the oil-soluble temporary plugging agent is capable of generating highly dispersed microparticles within water (attaining a dispersion degree at the micrometer scale), existing in the form of fine particles in water. This enables it to effectively seal the oil layer and preclude the intrusion of filtrate and harmful solid phases into the formation. On the other hand, after a specific time interval, it can gradually dissolve in crude oil, thereby alleviating the temporary plugging and rehabilitating the seepage channels of the reservoir. As illustrated in Fig. 4 , diverse oil-soluble temporary plugging agents display varying dissolution rates in kerosene at 70°C. Among them, the temporary plugging agent G325 exhibits an average oil solubility rate of 99.49%, demonstrating the most favorable effect. In contrast, the other two plugging agents, GN-362, are insoluble, and NFA-25 is only slightly soluble, which is disadvantageous for the subsequent reservoir plug removal operations on-site [ 26 ] . The oil-soluble temporary plugging agent G325, as shown in Fig. 3 , when dispersed in water, readily forms a milky white suspension. Particle size analysis research indicates that the proportion of particles smaller than 70 µ m is 70%. Moreover, the average expansion amount within 16 hours is less than 2.5 mm, and the linear expansion reduction rate exceeds 70%. Additionally, a self-degradable fluid loss additive, which was previously developed in the laboratory, was chosen to curtail the fluid loss of the drilling fluid system into the oil and gas reservoir. This further mitigates the damage inflicted on the Jurassic reservoir due to velocity sensitivity and water sensitivity. The specific experimental results are presented in Table 6 and Fig. 5 . The PPA plugging tester was employed indoors to assess the plugging rates of different fluid loss additives, including the oil-soluble temporary plugging agents G325, GN-362, NFA-25, ASP-1250, and the self-degradable fluid loss additive. The research findings reveal that the self-degradable fluid loss additive attains the highest plugging rate of 91.76%. When several of these products are compounded, the plugging rate reaches 92.94%. Table 6 Performance of drilling fluid treatment agent and instantaneous filtration loss of the system Serial number Nomenclature 7′30″ (mL) 30″ (mL) Spurt Loss Volume(mL) Plugging Rate of Fluid - loss Volume for Comparison Base Slurry % 1 Base slurry(3% bentonite + 0.2% PAc-H) 30 43 34 / 2 Base slurry + 1%G325 22 41.9 4.2 87.65% 3 Base slurry + 1%GN-362 4 5.3 5.4 84.12% 4 Base slurry + 1% self-degrading fluid loss reducer 2.2 3 2.8 91.76% 5 Base slurry + 1%ASP-1250 16 26 12 64.71% 6 Base slurry + 1%ASP-1250 + 1%G325 + 1% self-degrading fluid loss reducer 2.8 4.4 2.4 92.94% 7 Base slurry + 1%ASP-1250 + 1%G325 + 1%GN-362 3.5 5.1 3.8 88.82% The key reason why the self-degradable fluid loss additive, as well as its combination with the oil-soluble temporary plugging agent, possess excellent plugging and fluid loss properties lies in the fact that they form a favorable particle gradation with the Jurassic reservoirs in Zhenbei Oilfield [ 27 – 28 ] . As previously mentioned, the average pore diameter of the Jurassic reservoirs in Zhenbei Oilfield is 110.95 µ m. The particle size distribution curves of the oil-soluble temporary plugging agents G325, GN-362, NFA-25, the ultra-fine calcium carbonate temporary plugging agent, the fluid loss additive ASP-1250, and the self-degradable fluid loss additive are shown in Fig. 6 . The D50 and D90 values of the self-degradable fluid loss additive are 266.020 µ m and 516.672 µ m respectively, while those of the oil-soluble temporary plugging agent are 246.908 µ m and 612.670 µ m respectively. The range of the D90 value is between 18 µ m and 600 µ m, which meets the requirements for temporary plugging of the Jurassic reservoirs.In addition, with reference to the permeability and porosity of the Jurassic strata, a 500 mD rock slab was selected for plugging experiments under the conditions of 90°C and 500 psi for 30 minutes. Experiments were carried out by using clear water, base slurry + self-degradable fluid loss additive, and base slurry + self-degradable fluid loss additive + ASP-1250 to plug the rock slab respectively. The scanning electron microscope images of the rock slab after being plugged by different plugging media are shown in Fig. 7 . Compared with clear water, the latter two have already formed a dense plugging layer on the surface of the rock slab, which can effectively prevent the damage caused by particle migration due to velocity sensitivity within the reservoir, reduce the fluid loss of the drilling fluid system, and mitigate the reservoir damage caused by water sensitivity [ 29 – 30 ] . Therefore, the self-degradable fluid loss additive and its combination with the oil-soluble temporary plugging agent possess excellent plugging and fluid loss properties. Based on the comprehensive research and selection of oil-soluble temporary plugging agents and fluid loss additives, the composition of the Jurassic reservoir protection drilling fluid system has been determined. Specifically, it includes base slurry, viscosifier PAc-Lv, self-degradable fluid loss additive, ultra-fine calcium carbonate, and ASP-1250 and so on. 3.2.2 Performance of Reservoir Protection Drilling Fluid System Under laboratory conditions, comprehensive investigations were conducted on the fundamental performance and reservoir protection capabilities of the aforesaid Jurassic reservoir protection drilling fluid system. The basic performance parameters of the Jurassic reservoir protection drilling fluid system, as presented in Table 7 below, encompass density, medium-pressure fluid loss volume, apparent viscosity (AV), and plastic viscosity (PV). The research findings reveal that the composition of the Jurassic reservoir protection drilling fluid system exerts a relatively minor influence on its fundamental performance. The values of density, AV, and PV are approximately in proximity. Moreover, the incorporation of the rigid plugging material, namely ultra-fine calcium carbonate, is conducive to further diminishing the medium-pressure fluid loss of the drilling fluid system. Table 7 Basic performance of reservoir protection drilling fluid system Serial number Composition of reservoir protection drilling fluid Density(g/cm 3 ) FL API (mL) AV(mPa⸱s) PV(mPa⸱s) 1 Base slurry + 0.2%PAc-Lv + 1% Self-degrading fluid loss reducer + 1%G325 1.01 5.0 20 14 2 Base slurry + 0.2%PAc-Lv + 1% Self-degrading fluid loss reducer + 1%G325 + 1%ASP-1250 1.01 4.8 20 15 3 Base slurry + 0.2%PAc-Lv + 1% Self-degrading fluid loss reducer + 1%G325 + 1%ASP-1250 + 1%CaCO 3 1.01 4.5 20 15 The research results regarding the reservoir protection performance of the Jurassic reservoir protection drilling fluid system are shown in Table 8 and Fig. 8 . The average temporary plugging rate of the reservoir protection drilling fluid system is 71.06%, and the core permeability recovery rate is 97.80%, indicating excellent reservoir protection performance. In addition, the SEM scanning was carried out on the cores after reservoir damage to facilitate the observation of the blockage situation of pore throats. The results showed that the plugging end face of the core was dense, the pore throats were unobstructed after oil dissolution, and the inner walls of the pore throats were smooth without any attachments or adhesions. Therefore, the Jurassic reservoir protection drilling fluid constructed in this research can smoothly remove the blockage through reverse displacement under simulated formation pressure after temporary plugging and oil dissolution, which indicating outstanding reservoir protection performance [ 31 – 32 ] . Table 8 Evaluation test of core recovery rate for Jurassic reservoir protection Core ID K O1 ×10 − 3 µm 2 K O2 ×10 − 3 µm 2 K O3 ×10 − 3 µm 2 Temporary plugging rate (%) Restoration rate (%) A19 3.2718 0.9337 3.1744 71.46 97.02 3.2333 0.9399 3.1756 70.93 98.21 3.2333 0.9450 3.1745 70.77 98.18 Average value 3.2461 0.9395 3.1748 71.06 97.80 3.3 Field Application of Reservoir Protection Drilling Fluid System In 2022, the test outcomes of the aforementioned reservoir protection drilling fluid system within the Jurassic formations of the 11th Oil Production Plant are presented in Fig. 9 as follows. The results demonstrate that in 2021, the average test production volume of the Jurassic in the 11th Oil Production Plant was 12.23 cubic meters per day. Subsequent to the drilling operations conducted with the reservoir protection drilling fluid system in 2022, the average test production volume of the Jurassic in the 11th Oil Production Plant escalated to 18.55 cubic meters per day, signifying a production increment of approximately 51.68%. Evidently, the reservoir protection efficacy during the drilling process is highly significant. In addition, the reservoir protection drilling fluid was implemented in the field for horizontal well test oil applications in both the same well group and different well groups within the Zhen 470 Block and Pengyang Block of the Jurassic in the 11th Oil Production Plant. The corresponding results are presented in Fig. 10 . To begin with, in comparison with Tong 53-33S, Tong 52 − 32, and Tong 54 − 32 within the same well group in the Zhen 470 Block, the test oil production of the relevant well group exhibited an increment of 47.01% and 48.60% respectively. Subsequently, in the Pengyang Operating Area, the production of the horizontal well Yan 83 − 01 in distinct well groups was enhanced by 80.90% relative to that of Yan 90 − 31. Evidently, the reservoir protection effect is satisfactory, and the production enhancement effect is highly significant. 4. Conclusion In this study, based on a comprehensive examination of the reservoir physical property characteristics and an in-depth sensitivity evaluation of the Jurassic reservoirs within the Ordos Basin, the underlying damage mechanism of the drilling fluids to the Jurassic reservoirs in Zhenbei Oilfield was elucidated. Subsequently, extensive research and experimental investigations were conducted regarding the drilling fluid technology dedicated to the protection of Jurassic reservoirs. The average porosity of the Jurassic reservoirs is approximately 15%, and the permeability exceeds 100×10⁻³ µ m². These reservoirs fall into the category of low-porosity and medium-permeability reservoirs. Notably, the pore structures are predominantly composed of intergranular pores and dissolution pores, accompanied by a relatively low displacement pressure. Overall, the physical properties of these reservoirs exhibit a favorable condition. The sensitivity of the Jurassic reservoirs is primarily characterized by a moderately weak to velocity-sensitive nature. In terms of the specific severity of sensitivity, it follows the order of velocity sensitivity > water sensitivity > alkali sensitivity > acid sensitivity. The formation microparticles tend to migrate within the pores along with the filtrate and subsequently accumulate in the throats, thereby inducing blockages and leading to a reduction in permeability. A sophisticated set of drilling fluid technology for the protection of Jurassic reservoirs has been successfully developed. The fluid loss under medium pressure is precisely 4.5 mL, with an average plugging rate reaching 71.06% and an average core permeability recovery rate attaining 97.80%. As the oil and gas development progresses in the later stage, the temporary plugging layer will gradually dissolve and self-degrade, thereby restoring the unobstructed state of the pores and throats and effectively fulfilling the objective of reservoir protection. Declarations Data Availability/ Availability of Data and Materials The datasets used and/or analyzed during the current study available from the corresponding author on reasonable request. CRediT Authorship Contribution Statement Jingguang Wang : Conceptualization, Funding acquisition, Investigation, Writing-review & editing. Wang He : Writing-original draft, Writing-review & editing. Min Zhang : Methodology. Chen He : Validation. Peiming Shi : Data curation. Conflict of Interest The authors declare that there is no conflict of interest. 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Influence of reservoir physical properties on guar gum fracturing fluid damage in unconventional tight reservoirs. Phys. Fluids . 36 , 046608 (2024). Zhou, Y., Yang, W. & Yin, D. Experimental investigation on reservoir damage caused by clay minerals after water injection in low permeability sandstone reservoirs. J. Pet. Explor. Prod. Technol. 12 , 915–924 (2022). Okere, C. et al. Experimental study on the degree and damage-control mechanisms of fuzzy-ball-induced damage in single and multi-layer commingled tight reservoirs. Petrol. Sci. 20 , 3598–3609 (2023). Tan, Q., You, L., Kang, Y. & Xu, C. Formation damage mechanisms in tight carbonate reservoirs: The typical illustrations in Qaidam Basin and Sichuan Basin, China. Gas Sci. Eng. 95 , 104193 (2021). Zhou, X. et al. Wang. Study on pore structure and permeability sensitivity of tight oil reservoirs. Energy 288 , 129632 (2024). Yang, F. Sensitivity evaluation and stimulation optimization of ultralow permeability sandstone reservoir. 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Bageri, B., Adebayo, A., Jaberi, J. & Patil, S. Effect of perlite particles on the filtration properties of high-density barite weighted water-based drilling fluid. Powder Technol. 360 , 1157–1166 (2020). Jaberi, J., Bageri, B., Otain, W., Alsaleem, A. & Adebayo, A. Fine-tuning filter cake sealing performance: The role of particle size in hematite weighted water-based drilling fluid. ACS Omega . 9 , 25084–25093 (2024). Li, Y. et al. Experimental study on solid particle migration and production behaviors during marine natural gas hydrate dissociation by depressurization. Petrol. Sci. 20 , 3610–3623 (2023). Wang, L. et al. Water-sensitive damage mechanism and the injection water source optimization of low permeability sandy conglomerate reservoirs. Petrol. Explor. Dev+ . 46 , 1218–1230 (2019). Zhou, H., Wu, X., Song, Z., Zheng, B. & Zhang, K. A review on mechanism and adaptive materials of temporary plugging agent for chemical diverting fracturing. J. Petrol. Sci. Eng. 212 , 110256 (2022). Zhang, X., Deng, J. & Yang, K. High-strength and self-degradable sodium alginate/ polyacrylamide preformed particle gels for conformance control to enhance oil recovery. Petrol. Sci. 19 , 3149–3158 (2022). Table 5 Table 5 is available in the Supplementary Files section. Additional Declarations No competing interests reported. Supplementary Files Table5.docx Cite Share Download PDF Status: Published Journal Publication published 02 Feb, 2026 Read the published version in Scientific Reports → Version 1 posted Editorial decision: Revision requested 11 Jul, 2025 Reviews received at journal 06 Jun, 2025 Reviewers agreed at journal 05 Jun, 2025 Reviewers agreed at journal 04 Jun, 2025 Reviews received at journal 07 May, 2025 Reviewers agreed at journal 29 Apr, 2025 Reviewers invited by journal 24 Apr, 2025 Editor assigned by journal 24 Apr, 2025 Editor invited by journal 24 Apr, 2025 Submission checks completed at journal 17 Apr, 2025 First submitted to journal 17 Apr, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6426437","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":447503093,"identity":"7983d960-071c-48ca-bfe7-09f3a3fd8022","order_by":0,"name":"Jingguang Wang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA5klEQVRIiWNgGAWjYBACNvb2gw8+GPyXAzIOMHxgkCCshY/nTLLhjApmYyAjgXEGMVrkJBLMpHnOMCfOk0gwYOYhymE8BxIkZ7axGQMZqZtt/ljk8TcwP3uA3y+NBww+tvEA/dJ47HZum0SxxAE2cwNCtiTObJMA2ZJ2O7dBIrHhAA8bXh+xAb1wmLfNILEN6KnbFn8kEucTocWwGRhYEC1AbuIGglqAgcw4o+IA0GFn0m72tkkkbjzMZoZXi3x7+/EfHwwOyAEZx278+FOXOO948zMiYgcFMJOofhSMglEwCkYBJgAAcp1MpmSRg7wAAAAASUVORK5CYII=","orcid":"","institution":"National Engineering Laboratory for Exploration and Development of Low Permeability Oil and Gas Fields","correspondingAuthor":true,"prefix":"","firstName":"Jingguang","middleName":"","lastName":"Wang","suffix":""},{"id":447503094,"identity":"87142c23-ac94-4d13-87cb-207ffcc93851","order_by":1,"name":"Wang He","email":"","orcid":"","institution":"Engineering and Technology department of Changqing Oilfield Company","correspondingAuthor":false,"prefix":"","firstName":"Wang","middleName":"","lastName":"He","suffix":""},{"id":447503095,"identity":"d7c759ea-be1e-4550-b558-4094cd56fe38","order_by":2,"name":"Min Zhang","email":"","orcid":"","institution":"The 11th Oil Production Plant of CNPC Changqing Oilfield Company","correspondingAuthor":false,"prefix":"","firstName":"Min","middleName":"","lastName":"Zhang","suffix":""},{"id":447503096,"identity":"98ffd921-89f9-4764-9097-162cf07c7077","order_by":3,"name":"Chen He","email":"","orcid":"","institution":"The 11th Oil Production Plant of CNPC Changqing Oilfield Company","correspondingAuthor":false,"prefix":"","firstName":"Chen","middleName":"","lastName":"He","suffix":""},{"id":447503097,"identity":"32f75399-e3a3-4eae-99aa-5a984312bac8","order_by":4,"name":"Peiming Shi","email":"","orcid":"","institution":"Changqing Drilling Company, CNPC Chuanqing Drilling Engineering Co.,Ltd.,","correspondingAuthor":false,"prefix":"","firstName":"Peiming","middleName":"","lastName":"Shi","suffix":""}],"badges":[],"createdAt":"2025-04-11 08:38:08","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6426437/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6426437/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s41598-026-35924-5","type":"published","date":"2026-02-02T15:56:57+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":82137854,"identity":"c2b5cd64-4df0-4ca0-82e2-74d8462ed27a","added_by":"auto","created_at":"2025-05-07 06:21:23","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":231934,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eThe content of Jurassic reservoir in Zhenbei Oilfield (a: Clastic composition; b: Interstitial material)\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"image1.png","url":"https://assets-eu.researchsquare.com/files/rs-6426437/v1/146c4e488eda1217ef59101c.png"},{"id":82136503,"identity":"b1e9d14c-963d-46e7-bce8-c10b10a3b4bb","added_by":"auto","created_at":"2025-05-07 06:13:23","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":290117,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eMercury pressure curve of Jurassic reservoir in Zhenbei Oilfield\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"image2.png","url":"https://assets-eu.researchsquare.com/files/rs-6426437/v1/8a5b412de8e849e14740f208.png"},{"id":82136506,"identity":"86989976-8d42-4778-a4cd-4a9c8a1901f7","added_by":"auto","created_at":"2025-05-07 06:13:24","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":342135,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eParticle size distribution, expansion amount, and technical parameters of oil soluble temporary plugging agent G325\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"image3.png","url":"https://assets-eu.researchsquare.com/files/rs-6426437/v1/952cb3c0d28f2da81c5119fd.png"},{"id":82136501,"identity":"193fdc8d-124c-4a10-9cb6-474c89c0c535","added_by":"auto","created_at":"2025-05-07 06:13:23","extension":"jpeg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":66415,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eOil solubility of temporary plugging agents with different oil solubility\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"image4.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6426437/v1/8531d19902c0ba3332704023.jpeg"},{"id":82140105,"identity":"36e5a417-52d9-4c3c-9ca3-127f8659e4e5","added_by":"auto","created_at":"2025-05-07 06:29:24","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":86128,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eComparison effect diagram of filtration loss at different time periods\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"image5.png","url":"https://assets-eu.researchsquare.com/files/rs-6426437/v1/ea780f4c806bdfb136def15e.png"},{"id":82137858,"identity":"698cfcfb-2c2c-4ad4-8732-7f4a2ab98507","added_by":"auto","created_at":"2025-05-07 06:21:24","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":257384,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eParticle size distribution curve (\u003c/strong\u003e\u003cem\u003e\u003cstrong\u003ea\u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003e: CaCO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e3\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e; \u003c/strong\u003e\u003cem\u003e\u003cstrong\u003eb\u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003e: G325; \u003c/strong\u003e\u003cem\u003e\u003cstrong\u003ec\u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003e: GN-362; \u003c/strong\u003e\u003cem\u003e\u003cstrong\u003ed\u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003e: Self-degrading fluid loss reducer; \u003c/strong\u003e\u003cem\u003e\u003cstrong\u003ee\u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003e: NFA-25; \u003c/strong\u003e\u003cem\u003e\u003cstrong\u003ef\u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003e: ASP-1250)\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"image6.png","url":"https://assets-eu.researchsquare.com/files/rs-6426437/v1/bba1404e62a46c4550696742.png"},{"id":82144426,"identity":"85c675cf-fcb6-4645-b906-114bcc2a9617","added_by":"auto","created_at":"2025-05-07 06:45:24","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":212565,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eSEM (\u003c/strong\u003e\u003cem\u003e\u003cstrong\u003ea\u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003e: clean water; \u003c/strong\u003e\u003cem\u003e\u003cstrong\u003eb\u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003e: base slurry + self-degradable filter loss reducer; \u003c/strong\u003e\u003cem\u003e\u003cstrong\u003ec\u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003e: base slurry + self-degradable filter loss reducer + ASP-1250)\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"image7.png","url":"https://assets-eu.researchsquare.com/files/rs-6426437/v1/1325021d4fd78de1bd1b5fc6.png"},{"id":82136521,"identity":"d9c23e4d-432d-4f44-9259-228d964696d4","added_by":"auto","created_at":"2025-05-07 06:13:24","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":299770,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eSEM of temporary plugging end face of rock core (\u003c/strong\u003e\u003cem\u003e\u003cstrong\u003ea\u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003e: after damage;\u003c/strong\u003e\u003cem\u003e\u003cstrong\u003e b\u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003e: after oil dissolution)\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"image8.png","url":"https://assets-eu.researchsquare.com/files/rs-6426437/v1/fe37b4975bd4f9c81f20b3d9.png"},{"id":82137864,"identity":"bb91df1a-2556-4381-a22c-81d4692578a4","added_by":"auto","created_at":"2025-05-07 06:21:24","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":348619,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eOil testing results of Jurassic System in eleventh factory (\u003c/strong\u003e\u003cem\u003e\u003cstrong\u003ea\u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003e: 2021; \u003c/strong\u003e\u003cem\u003e\u003cstrong\u003eb\u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003e:2022)\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"image9.png","url":"https://assets-eu.researchsquare.com/files/rs-6426437/v1/1e7bc91560e8a05bbebfee93.png"},{"id":82136512,"identity":"9bfefd8b-440e-4142-9820-aefd024512b7","added_by":"auto","created_at":"2025-05-07 06:13:24","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":140594,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eOn site application of horizontal well oil testing in the same well group (\u003c/strong\u003e\u003cem\u003e\u003cstrong\u003ea\u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003e) and different well groups (\u003c/strong\u003e\u003cem\u003e\u003cstrong\u003eb\u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003e)\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"image10.png","url":"https://assets-eu.researchsquare.com/files/rs-6426437/v1/a3d53137beaa6fe0dc0caf55.png"},{"id":102233960,"identity":"f18d2714-0b58-4ae4-8699-1b6287d4f3f5","added_by":"auto","created_at":"2026-02-09 16:00:33","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3987545,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6426437/v1/3df0e5d4-f409-453c-965d-db68b5677ee9.pdf"},{"id":82136500,"identity":"922b3a1e-55e0-415e-8195-650d464bbc96","added_by":"auto","created_at":"2025-05-07 06:13:23","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":17877,"visible":true,"origin":"","legend":"","description":"","filename":"Table5.docx","url":"https://assets-eu.researchsquare.com/files/rs-6426437/v1/73c3711ee2415333a72865dd.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Research on the Damage Mechanism and Reservoir Protection Drilling Fluid System of Jurassic Reservoir in Zhenbei Oilfield","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe status of low-permeability oil and gas reservoirs in China's oil and gas exploration and development has become increasingly prominent and represents a crucial area for reserve augmentation. The Yanchang Formation within the Ordos Basin harbors abundant oil and gas resources within its low-permeability reservoirs \u003csup\u003e[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]\u003c/sup\u003e. Zhenbei Oilfield, located in the Longdong region of Gansu Province, is structurally positioned in the southwestern portion of the Yishan Slope in the Ordos Basin. The oil exploration activities in Zhenbei Oilfield initiated in the 1970s, and industrial oil flows have been achieved in formations such as Chang 3 and Chang 8, thereby exhibiting substantial exploration potential. In recent years, the practice of oil and gas exploration and development has substantiated that Zhenbei Oilfield is among the principal oil and gas enrichment zones. It has been ascertained that the reservoir physical properties of formations like Chang 3 are favorable, and the production from oil testing and trial production is relatively high, indicating a promising outlook for reserve increment and production enhancement \u003csup\u003e[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]\u003c/sup\u003e. The ancient geomorphology in the Zhenbei area predominantly comprises highlands, slopes, river valleys, and tributary gullies. Jurassic reservoirs are chiefly distributed on the slopes and slope mouths flanking the Zhenbei tributary river and the Yanwu tributary river. Jurassic reservoirs are widely dispersed across the basin. The reservoir physical properties are mainly manifested as intergranular pores and dissolution pores, with a relatively low displacement pressure, low porosity yet high permeability, and an overall satisfactory physical property profile. When external solid and liquid phases intrude, it is prone to trigger the migration of throat particles, leading to pore clogging and significant reservoir damage \u003csup\u003e[\u003cspan additionalcitationids=\"CR4\" citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe Fuxian Formation and the Yan 10-Yan 8 oil-bearing formations within the Jurassic strata in the Longdong area of the Ordos Basin constitute the primary oil-producing layers in this region. In comparison with the Yanchang Formation reservoirs, the Jurassic reservoirs possess the advantages of lower development costs and better comprehensive benefits \u003csup\u003e[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]\u003c/sup\u003e. In the Changqing Oilfield, the production proportion of Jurassic reservoirs has been progressively increasing year by year. In 2022, the proportion of annual production construction scale exceeded 30%, and it has emerged as a key stratum for the oilfield company to augment reserves and boost production, playing a vital role in the oilfield's production augmentation and stable production. In the process of oil and gas resource exploration and development of Jurassic reservoirs, the design and research and development of reservoir protection drilling fluid systems are the linchpins for ensuring the release of oil and gas production capacity \u003csup\u003e[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]\u003c/sup\u003e. The evolution of drilling fluid systems has traversed from the initial clear water and polymer drilling fluids to the more prevalently applied sulfonated drilling fluids and oil-based drilling fluids, as well as the environmentally friendly drilling fluid systems developed to meet the corresponding environmental protection and long-term development requisites \u003csup\u003e[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]\u003c/sup\u003e. Oil and gas reservoir protection is a comprehensive and systematic project, and the design and optimization of drilling fluid systems are of paramount importance. The principal reservoir protection drilling fluid technologies encompass positive colloid drilling fluids, synthetic-based drilling fluids, formate drilling fluids, and polyalcohol drilling fluids, among others \u003csup\u003e[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]\u003c/sup\u003e. However, these drilling fluids are less commonly utilized in Jurassic reservoirs. Jia Shengguo addressed the technical conundrums of the low-porosity and low-permeability reservoirs in the Toutunhe Formation of the Jurassic in the Fudong Slope area, where the shale content in the reservoir rocks is elevated, hydration expansion is liable to occur, thereby inducing complex downhole conditions and posing difficulties in reservoir protection. Through comprehensive reservoir sensitivity prediction and diverse sensitivity evaluations, he proposed improvement strategies for the formulation design and optimization of the reservoir protection drilling fluid system for on-site construction, with a particular emphasis on fortifying its inhibition and plugging capabilities. The permeability recovery value of reservoir core dynamic pollution damage can reach 83% \u003csup\u003e[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]\u003c/sup\u003e. Zhang Rui et al. took the Chang 8 reservoir in the Wuqi area of the Ordos Basin as the research target and developed a suite of reservoir protection measures for safeguarding the Wuqi Oilfield. Specifically, temporary plugging agents SLD-1 and EL-1 that match the reservoir pores and pore throat structures, as well as oil layer protection agents TYZ-7 and JYP were selected \u003csup\u003e[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]\u003c/sup\u003e. Dong Hongwei et al. confronted the current situation where the physical properties of the Yan'an Formation in certain blocks of the Longdong Oilfield are favorable, yet the production is relatively low. The root cause was identified as the inability of the drilling fluid system during drilling operations to achieve reservoir protection. Subsequently, in combination with the oil layer protection agent PWTBA - Ⅱ, a novel reservoir protection drilling fluid technology was developed, reducing the damage rate to the oil and gas reservoir to 10.61% \u003csup\u003e[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]\u003c/sup\u003e. In summary, it is evident that the design and optimization of oil and gas reservoir protection drilling fluid systems are primarily accomplished through reservoir sensitivity prediction and sensitivity evaluation, along with the reinforcement of the plugging performance, filtration loss performance, anti-collapse performance of the drilling fluid systems.\u003c/p\u003e \u003cp\u003eIn light of the foregoing, this study, in alignment with the reserve augmentation and production escalation imperatives of the oilfield enterprise and leveraging the production superiority of Jurassic reservoirs, undertakes an evaluation of the diverse sensitivities exhibited by Jurassic reservoirs within the Ordos Basin. Thereby, the damage mechanism inherent in the Jurassic reservoirs of Zhenbei Oilfield is unveiled. Concurrently, investigations and trials pertaining to the drilling fluid technology for safeguarding Jurassic reservoirs are conducted, with the overarching objective of attenuating reservoir impairment and augmenting the efficacy of oilfield exploitation.\u003c/p\u003e"},{"header":"2. Experiment","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Materials\u003c/h2\u003e \u003cdiv id=\"Sec4\" class=\"Section3\"\u003e \u003ch2\u003e2.1.1 Chemical reagents\u003c/h2\u003e \u003cp\u003eThe rock samples of Jurassic reservoirs, together with the plugging agents G325 and GN362 utilized in drilling fluids, ultra-fine calcium carbonate (CaCO\u003csub\u003e3\u003c/sub\u003e), self-degradable fluid loss additives, fluid loss additive NFA-25, fluid loss additive ASP-1250, and bentonite, were all furnished by the oil production plants or the Engineering Technology Management Department of Changqing Oilfield. Meanwhile, the analytical reagent-grade chemicals such as sodium carbonate and sodium hydroxide were procured from Chengdu Kelong Chemicals Co., Ltd.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section3\"\u003e \u003ch2\u003e2.1.2 Others\u003c/h2\u003e \u003cp\u003eDYG-II multifunctional core displacement experimental device, AutoPore9600/9510 high-performance fully automatic mercury intrusion porosimeter, FlexSEM1000 compact intelligent scanning electron microscope, X Pert PRO MPD X-ray diffractometer, Master sizer 2000 laser particle size analyzer, PPA plugging tester, etc.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Experimental Method\u003c/h2\u003e \u003cp\u003eThe physical property parameters, mineral composition, and pore structure of the Jurassic reservoir rock samples were all determined in accordance with the existing conventional experimental methods. The reservoir sensitivity evaluation was carried out referring to the industry standard SY/T 5358\u0026thinsp;\u0026minus;\u0026thinsp;2010 \"Evaluation Method of Reservoir Sensitivity Flow Experiment\". The performance evaluation of the reservoir protection drilling fluid system was implemented with reference to GB/T 29170\u0026thinsp;\u0026minus;\u0026thinsp;2012 \"Petroleum and Natural Gas Industry-Laboratory Testing of Drilling Fluids\".\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results and Discussion","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Damage Mechanism of Jurassic Reservoirs\u003c/h2\u003e \u003cdiv id=\"Sec9\" class=\"Section3\"\u003e \u003ch2\u003e3.1.1 Reservoir physical property parameters\u003c/h2\u003e \u003cp\u003eThe reservoir physical property parameters of the Jurassic reservoirs (including Yan 4, Yan 5, Yan 6, Yan 7, Yan 8, Yan 9 and Yan 10) in the No. 11 Oil Production Plant and the Jurassic reservoirs (Yan 8, Yan 9 and Yan 10) in the No. 2 Oil Production Plant were studied. The experimental results are shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e below. The research results indicated that the average porosity of the Jurassic reservoirs in the No. 11 Oil Production Plant is 14.4%, and that of the Jurassic reservoirs in the No. 2 Oil Production Plant is 16.0%. In addition, the average permeability of the Jurassic reservoirs in the No. 11 Oil Production Plant is 183.9\u0026times;10⁻\u0026sup3; \u0026micro;m\u0026sup2;, and the average permeability of the No. 2 Oil Production Plant is 133.1\u0026times;10⁻\u0026sup3; \u003cem\u003e\u0026micro;\u003c/em\u003em\u0026sup2;. Based on the comprehensive porosity and permeability data, it can be seen that the Jurassic reservoirs are all low-porosity and medium-permeability reservoirs, which are more prone to damage caused by blockage of external solid particles \u003csup\u003e[\u003cspan additionalcitationids=\"CR14 CR15\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003ePhysical properties parameters of Jurassic reservoirs\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"9\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eOil Production Plant\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eHorizon\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNumber of samples\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c6\" namest=\"c4\"\u003e \u003cp\u003ePorosity(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c9\" namest=\"c7\"\u003e \u003cp\u003ePermeability(mD)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eArea\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eAverage value\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMinimum value\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eMaximum value\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eAverage value\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003eMinimum value\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003eMaximum value\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"5\" rowspan=\"6\"\u003e \u003cp\u003eThe 11th Oil Production Plant\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eYan 4\u0026thinsp;+\u0026thinsp;5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e280\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e16.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e24.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e408.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e914.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eYan 6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e312\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e14.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e22.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e153.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e430.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eYan 7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e270\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e14.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e22.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e184.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e553.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eYan 8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e932\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e14.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e21.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e304.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e927.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eYan 9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e775\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e13.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e19.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e48.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e172.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eYan 10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e128\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e13.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e25.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e3.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e165.7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eThe 2nd Oil Production Plant\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eYan 8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e15.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e10.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e17.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e77.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e1.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e520.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eYan 9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e256\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e16.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e23.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e207.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e1.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e2730.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eYan 10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e353\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e16.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e10.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e19.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e113.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e1.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e3961.9\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section3\"\u003e \u003ch2\u003e3.1.2 Characteristics of reservoir rocks\u003c/h2\u003e \u003cp\u003eThe research on reservoir characteristics serves as the fundamental basis for a series of crucial aspects in the field of oil and gas, including reservoir evaluation and prediction, as well as oilfield development and program readjustment. In-depth analyses and investigations were specifically conducted on the clastic component contents and interstitial material contents within the Jurassic reservoirs of Zhenbei Oilfield. The corresponding experimental outcomes are presented in Tables\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e and \u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, along with Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eStatistical table of clastic composition content of Jurassic reservoir in Zhenbei Oilfield\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"9\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eHorizon\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNumber of samples\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"6\" nameend=\"c8\" namest=\"c3\"\u003e \u003cp\u003eClastic composition (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eThe Others (%)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLump\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eQuartz Group\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eFeldspar Group\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eTotal Cuttings\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eIgneous Rock Cuttings\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eMetamorphic Rock Cuttings\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eSedimentary Rock Cuttings\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYan 4\u0026thinsp;+\u0026thinsp;5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e62.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e18.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e14.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e12.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e1.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYan 6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e55.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e19.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e17.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e1.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e7.7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYan 7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e55.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e13.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e19.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e16.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e2.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e10.9\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYan 8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e48\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e54.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e14.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e16.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e14.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e1.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e13.8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYan 9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e54.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e14.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e18.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e15.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e2.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e12.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYan 10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e57\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e50.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e8.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e21.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e11.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e8.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e19.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eStatistical table of interstitial material content of Jurassic reservoir in Zhenbei Oilfield\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"10\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eHorizon\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNumber of samples\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"7\" nameend=\"c9\" namest=\"c3\"\u003e \u003cp\u003eClastic composition (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eTotal\u003c/p\u003e \u003cp\u003e(%)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLump\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eKaolinite\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eHydromica\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eChlorite\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eCalcite\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eFerrocalcite\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eSiliceous\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eDolomite\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYan 4\u0026thinsp;+\u0026thinsp;5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e1.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e1.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e1.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e8.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYan 6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e1.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e1.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e0.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e9.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYan 7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e1.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e2.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e2.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e10.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYan 8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e2.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e1.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e1.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e0.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e11.7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYan 9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e2.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e1.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e1.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e1.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e12.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYan 10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e57\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e3.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e0.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e13.1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, Tables\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e and \u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, conspicuously revealed the predominant lithology of the Jurassic reservoirs within Zhenbei Oilfield is medium-to-fine grained quartz and feldspar lithic sandstones, with a proportion ranging from 59.4 to 80.4%. The interstitial substances are principally constituted by hydromica, silica, and kaolinite. Notably, kaolinite exhibits a rather feeble resistance to mechanical forces, and the interlayer bonding within its crystal structure is tenuous. When subjected to the impingement of high-velocity fluid flows, it undergoes dissociation, cleavage, and dispersion, thereby generating flaky microparticles. This phenomenon leads to the dispersion and migration of solid phases \u003csup\u003e[\u003cspan additionalcitationids=\"CR18\" citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]\u003c/sup\u003e, subsequently diminishing the reservoir permeability and ultimately inflicting damage upon the Jurassic reservoirs of Zhenbei Oilfield.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section3\"\u003e \u003ch2\u003e3.1.3 Reservoir pore structure\u003c/h2\u003e \u003cp\u003eThe study of reservoir pore structure characteristics has become a crucial part in reservoir characteristic research and is closely related to reservoir evaluation and oil and gas productivity prediction. During this research, a quantitative analysis was carried out on the pore types, pore throat sizes, etc. of Zhenbei Oilfield, such as porosity, permeability, intergranular pores, intercrystalline pores, etc. The specific details are shown in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e below, and the mercury injection curve of the Jurassic reservoir in Zhenbei Oilfield is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003ePore structure characteristics of Jurassic reservoirs in Zhenbei Oilfield\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"13\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c12\" colnum=\"12\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c13\" colnum=\"13\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eHorizon\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eArea\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ePorosity (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ePermeability\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eIntergranular pore\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eIntercrystalline pore\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eMicrocrack\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"5\" nameend=\"c12\" namest=\"c8\"\u003e \u003cp\u003eDissolution pore\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c13\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ePore - area percentage (%)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eIntergranular dissolution pores\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eFeldspar dissolution pores\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003eCuttings dissolution pores\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c11\"\u003e \u003cp\u003eMatrix dissolution pores\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c12\"\u003e \u003cp\u003eMinor total\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYan 4\u0026thinsp;+\u0026thinsp;5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e280\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e16.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e408.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e9.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e1.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e1.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e0.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c12\"\u003e \u003cp\u003e2.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c13\"\u003e \u003cp\u003e12.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYan 6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e312\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e14.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e153.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e6.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e1.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e0.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e0.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c12\"\u003e \u003cp\u003e2.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c13\"\u003e \u003cp\u003e8.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYan 7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e270\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e14.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e184.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e5.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e1.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e0.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e0.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c12\"\u003e \u003cp\u003e1.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c13\"\u003e \u003cp\u003e7.8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYan 8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e932\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e14.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e304.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e7.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e1.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e0.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e0.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c12\"\u003e \u003cp\u003e2.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c13\"\u003e \u003cp\u003e10.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYan 9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e775\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e13.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e48.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e8.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e1.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e0.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e0.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e0.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c12\"\u003e \u003cp\u003e2.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c13\"\u003e \u003cp\u003e11.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYan 10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e128\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e13.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e8.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e0.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e0.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e \u003cp\u003e0.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c12\"\u003e \u003cp\u003e2.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c13\"\u003e \u003cp\u003e11.8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe pore structure characteristics and mercury injection curves of the Jurassic reservoirs in Zhenbei Oilfield are exhibited as presented above. The porosity values are situated within the range of 13.0 to 16.2%. Notably, a substantial disparity in permeability is observed among different stratigraphic horizons. The mean value of planar porosity amounts to 10.4%, and in specific localized regions, it can ascend above 11%. Furthermore, as depicted in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, the pore types of the Jurassic reservoirs are predominantly intergranular pores and dissolution pores. The intergranular pores manifest in diverse forms such as triangular, polygonal, and irregular shapes. The dissolution pores are frequently elongated or assume a harbor-like morphology, and the connectivity of pore throats exhibits significant variability. These two types of pores both exert a favorable influence on enhancing the porosity and permeability of the reservoirs \u003csup\u003e[\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]\u003c/sup\u003e. Consequently, the overall physical properties of the Jurassic reservoirs in Zhenbei Oilfield are relatively favorable. In addition, the mercury injection curves disclose that the displacement pressure is comparatively low, thereby facilitating the backflow treatment process.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section3\"\u003e \u003ch2\u003e3.1.4 Reservoir Sensitivity Evaluation\u003c/h2\u003e \u003cp\u003eUnder laboratory conditions, a series of in-depth studies were meticulously carried out to assess the sensitivity of the Jurassic reservoirs in Zhenbei Oilfield, with a particular focus on velocity sensitivity, water sensitivity, alkali sensitivity, and acid sensitivity \u003csup\u003e[\u003cspan additionalcitationids=\"CR22\" citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]\u003c/sup\u003e. The experimental results are detailed in Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e provided hereinafter. In strict accordance with industry standards and by meticulously analyzing the evaluation indices for velocity sensitivity, water sensitivity, alkali sensitivity, and acid sensitivity, it has been ascertained that the velocity sensitivity damage of the Jurassic reservoirs in Zhenbei Oilfield is of a moderately weak nature. Similarly, the water sensitivity damage also demonstrates a moderately weak propensity, with an average damage rate recorded at 31.33%. When the pH value attains 14, the average damage rate is measured as 40.77%, which is designated as moderately weak damage. At a pH value of 10, the average damage rate is 15.46%, signifying a weak alkali sensitivity. Moreover, the acid sensitivity of the Jurassic reservoirs is classified as weak acid sensitivity. Based on the comprehensive and detailed evaluations of velocity sensitivity, water sensitivity, alkali sensitivity, and acid sensitivity, the hierarchical order of the severity of sensitivity of the Jurassic reservoirs is conclusively determined as follows: velocity sensitivity\u0026thinsp;\u0026gt;\u0026thinsp;water sensitivity\u0026thinsp;\u0026gt;\u0026thinsp;alkali sensitivity\u0026thinsp;\u0026gt;\u0026thinsp;acid sensitivity.\u003c/p\u003e \u003cp\u003eBased on the analyses of the physical properties, rock characteristics, pore structure, and sensitivity of the Jurassic reservoirs in Zhenbei Oilfield, it can be concluded that the Jurassic reservoirs are low-porosity and medium-permeability oil reservoirs. The intrusion of external solid and liquid phases into the formation is prone to causing reservoir damage. Moreover, the rock characteristics are mainly dominated by quartz and feldspar, and the interstitial materials are primarily composed of kaolinite. Kaolinite has relatively weak resistance to mechanical forces, and the connection between crystal layers is tenuous. Under the impact of high-velocity fluids, it will lead to dissociation, splitting, and dispersion to form flaky particles, resulting in dispersion and migration, which will reduce the reservoir permeability and also easily cause reservoir damage. In addition, the velocity sensitivity and water sensitivity of the reservoirs are relatively prominent, which can cause the hydration expansion, dispersion, and migration of particles in the reservoir, and block the pore throats, thereby leading to a decline in the reservoir permeability \u003csup\u003e[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Jurassic Reservoir Protection Drilling Fluid\u003c/h2\u003e \u003cdiv id=\"Sec14\" class=\"Section3\"\u003e \u003ch2\u003e3.2.1 Construction of Reservoir Protection Drilling Fluid System\u003c/h2\u003e \u003cp\u003eIn order to avert the infiltration of external solid and liquid phases into the formation and the damage resulting from particle migration within the reservoir due to velocity sensitivity, a highly efficient drilling fluid technology characterized by robust plugging capabilities, low fluid loss, and oil solubility has been formulated during the research process. The overarching objective is to enable the gradual dissolution and self-degradation of the drilling fluid as the development progresses in the later stages, thereby reinstating the unobstructed state of pore throats and accomplishing the goal of reservoir protection. The crucial aspects in the R \u0026amp; D of this drilling fluid technology are twofold. Firstly, it entails the meticulous selection of temporary plugging agents that are precisely commensurate with the pore dimensions of the Jurassic reservoirs. Secondly, it involves the painstaking research and identification of appropriate self-degrading fluid loss additives, with the aim of curtailing the invasion of external fluids.\u003c/p\u003e \u003cp\u003eOn the one hand, the oil-soluble temporary plugging agent is capable of generating highly dispersed microparticles within water (attaining a dispersion degree at the micrometer scale), existing in the form of fine particles in water. This enables it to effectively seal the oil layer and preclude the intrusion of filtrate and harmful solid phases into the formation. On the other hand, after a specific time interval, it can gradually dissolve in crude oil, thereby alleviating the temporary plugging and rehabilitating the seepage channels of the reservoir. As illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, diverse oil-soluble temporary plugging agents display varying dissolution rates in kerosene at 70\u0026deg;C. Among them, the temporary plugging agent G325 exhibits an average oil solubility rate of 99.49%, demonstrating the most favorable effect. In contrast, the other two plugging agents, GN-362, are insoluble, and NFA-25 is only slightly soluble, which is disadvantageous for the subsequent reservoir plug removal operations on-site \u003csup\u003e[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]\u003c/sup\u003e. The oil-soluble temporary plugging agent G325, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, when dispersed in water, readily forms a milky white suspension. Particle size analysis research indicates that the proportion of particles smaller than 70 \u003cem\u003e\u0026micro;\u003c/em\u003em is 70%. Moreover, the average expansion amount within 16 hours is less than 2.5 mm, and the linear expansion reduction rate exceeds 70%. Additionally, a self-degradable fluid loss additive, which was previously developed in the laboratory, was chosen to curtail the fluid loss of the drilling fluid system into the oil and gas reservoir. This further mitigates the damage inflicted on the Jurassic reservoir due to velocity sensitivity and water sensitivity. The specific experimental results are presented in Table\u0026nbsp;\u003cspan refid=\"Tab6\" class=\"InternalRef\"\u003e6\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e. The PPA plugging tester was employed indoors to assess the plugging rates of different fluid loss additives, including the oil-soluble temporary plugging agents G325, GN-362, NFA-25, ASP-1250, and the self-degradable fluid loss additive. The research findings reveal that the self-degradable fluid loss additive attains the highest plugging rate of 91.76%. When several of these products are compounded, the plugging rate reaches 92.94%.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab6\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 6\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003ePerformance of drilling fluid treatment agent and instantaneous filtration loss of the system\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSerial number\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNomenclature\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7\u0026prime;30\u0026Prime;\u003c/p\u003e \u003cp\u003e(mL)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e30\u0026Prime;\u003c/p\u003e \u003cp\u003e(mL)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eSpurt Loss Volume(mL)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePlugging Rate of Fluid - loss Volume for Comparison Base Slurry %\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBase slurry(3% bentonite\u0026thinsp;+\u0026thinsp;0.2% PAc-H)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e43\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e34\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e/\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBase slurry\u0026thinsp;+\u0026thinsp;1%G325\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e41.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e87.65%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBase slurry\u0026thinsp;+\u0026thinsp;1%GN-362\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e5.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e84.12%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBase slurry\u0026thinsp;+\u0026thinsp;1% self-degrading fluid loss reducer\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e91.76%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBase slurry\u0026thinsp;+\u0026thinsp;1%ASP-1250\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e64.71%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBase slurry\u0026thinsp;+\u0026thinsp;1%ASP-1250\u0026thinsp;+\u0026thinsp;1%G325\u0026thinsp;+\u0026thinsp;1% self-degrading fluid loss reducer\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e92.94%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBase slurry\u0026thinsp;+\u0026thinsp;1%ASP-1250\u0026thinsp;+\u0026thinsp;1%G325\u0026thinsp;+\u0026thinsp;1%GN-362\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e88.82%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe key reason why the self-degradable fluid loss additive, as well as its combination with the oil-soluble temporary plugging agent, possess excellent plugging and fluid loss properties lies in the fact that they form a favorable particle gradation with the Jurassic reservoirs in Zhenbei Oilfield \u003csup\u003e[\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]\u003c/sup\u003e. As previously mentioned, the average pore diameter of the Jurassic reservoirs in Zhenbei Oilfield is 110.95 \u003cem\u003e\u0026micro;\u003c/em\u003em. The particle size distribution curves of the oil-soluble temporary plugging agents G325, GN-362, NFA-25, the ultra-fine calcium carbonate temporary plugging agent, the fluid loss additive ASP-1250, and the self-degradable fluid loss additive are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e. The D50 and D90 values of the self-degradable fluid loss additive are 266.020 \u003cem\u003e\u0026micro;\u003c/em\u003em and 516.672 \u003cem\u003e\u0026micro;\u003c/em\u003em respectively, while those of the oil-soluble temporary plugging agent are 246.908 \u003cem\u003e\u0026micro;\u003c/em\u003em and 612.670 \u003cem\u003e\u0026micro;\u003c/em\u003em respectively. The range of the D90 value is between 18 \u003cem\u003e\u0026micro;\u003c/em\u003em and 600 \u003cem\u003e\u0026micro;\u003c/em\u003em, which meets the requirements for temporary plugging of the Jurassic reservoirs.In addition, with reference to the permeability and porosity of the Jurassic strata, a 500 mD rock slab was selected for plugging experiments under the conditions of 90\u0026deg;C and 500 psi for 30 minutes. Experiments were carried out by using clear water, base slurry\u0026thinsp;+\u0026thinsp;self-degradable fluid loss additive, and base slurry\u0026thinsp;+\u0026thinsp;self-degradable fluid loss additive\u0026thinsp;+\u0026thinsp;ASP-1250 to plug the rock slab respectively. The scanning electron microscope images of the rock slab after being plugged by different plugging media are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e. Compared with clear water, the latter two have already formed a dense plugging layer on the surface of the rock slab, which can effectively prevent the damage caused by particle migration due to velocity sensitivity within the reservoir, reduce the fluid loss of the drilling fluid system, and mitigate the reservoir damage caused by water sensitivity \u003csup\u003e[\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]\u003c/sup\u003e. Therefore, the self-degradable fluid loss additive and its combination with the oil-soluble temporary plugging agent possess excellent plugging and fluid loss properties.\u003c/p\u003e \u003cp\u003eBased on the comprehensive research and selection of oil-soluble temporary plugging agents and fluid loss additives, the composition of the Jurassic reservoir protection drilling fluid system has been determined. Specifically, it includes base slurry, viscosifier PAc-Lv, self-degradable fluid loss additive, ultra-fine calcium carbonate, and ASP-1250 and so on.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section3\"\u003e \u003ch2\u003e3.2.2 Performance of Reservoir Protection Drilling Fluid System\u003c/h2\u003e \u003cp\u003eUnder laboratory conditions, comprehensive investigations were conducted on the fundamental performance and reservoir protection capabilities of the aforesaid Jurassic reservoir protection drilling fluid system. The basic performance parameters of the Jurassic reservoir protection drilling fluid system, as presented in Table\u0026nbsp;\u003cspan refid=\"Tab7\" class=\"InternalRef\"\u003e7\u003c/span\u003e below, encompass density, medium-pressure fluid loss volume, apparent viscosity (AV), and plastic viscosity (PV). The research findings reveal that the composition of the Jurassic reservoir protection drilling fluid system exerts a relatively minor influence on its fundamental performance. The values of density, AV, and PV are approximately in proximity. Moreover, the incorporation of the rigid plugging material, namely ultra-fine calcium carbonate, is conducive to further diminishing the medium-pressure fluid loss of the drilling fluid system.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab7\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 7\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eBasic performance of reservoir protection drilling fluid system\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSerial number\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eComposition of reservoir protection drilling fluid\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eDensity(g/cm\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eFL\u003csub\u003eAPI\u003c/sub\u003e(mL)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eAV(mPa⸱s)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePV(mPa⸱s)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBase slurry\u0026thinsp;+\u0026thinsp;0.2%PAc-Lv\u0026thinsp;+\u0026thinsp;1% Self-degrading fluid loss reducer\u0026thinsp;+\u0026thinsp;1%G325\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e14\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBase slurry\u0026thinsp;+\u0026thinsp;0.2%PAc-Lv\u0026thinsp;+\u0026thinsp;1% Self-degrading fluid loss reducer\u0026thinsp;+\u0026thinsp;1%G325\u0026thinsp;+\u0026thinsp;1%ASP-1250\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBase slurry\u0026thinsp;+\u0026thinsp;0.2%PAc-Lv\u0026thinsp;+\u0026thinsp;1% Self-degrading fluid loss reducer\u0026thinsp;+\u0026thinsp;1%G325\u0026thinsp;+\u0026thinsp;1%ASP-1250\u0026thinsp;+\u0026thinsp;1%CaCO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe research results regarding the reservoir protection performance of the Jurassic reservoir protection drilling fluid system are shown in Table\u0026nbsp;\u003cspan refid=\"Tab8\" class=\"InternalRef\"\u003e8\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e. The average temporary plugging rate of the reservoir protection drilling fluid system is 71.06%, and the core permeability recovery rate is 97.80%, indicating excellent reservoir protection performance. In addition, the SEM scanning was carried out on the cores after reservoir damage to facilitate the observation of the blockage situation of pore throats. The results showed that the plugging end face of the core was dense, the pore throats were unobstructed after oil dissolution, and the inner walls of the pore throats were smooth without any attachments or adhesions. Therefore, the Jurassic reservoir protection drilling fluid constructed in this research can smoothly remove the blockage through reverse displacement under simulated formation pressure after temporary plugging and oil dissolution, which indicating outstanding reservoir protection performance \u003csup\u003e[\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab8\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 8\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eEvaluation test of core recovery rate for Jurassic reservoir protection\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCore ID\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eK\u003c/em\u003e\u003csub\u003e\u003cem\u003eO1\u003c/em\u003e\u003c/sub\u003e\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e\u0026micro;m\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cem\u003eK\u003c/em\u003e\u003csub\u003e\u003cem\u003eO2\u003c/em\u003e\u003c/sub\u003e\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e\u0026micro;m\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eK\u003c/em\u003e\u003csub\u003e\u003cem\u003eO3\u003c/em\u003e\u003c/sub\u003e\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e\u0026micro;m\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eTemporary plugging rate (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eRestoration rate (%)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eA19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.2718\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.9337\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.1744\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e71.46\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e97.02\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.2333\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.9399\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.1756\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e70.93\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e98.21\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.2333\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.9450\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.1745\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e70.77\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e98.18\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAverage value\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.2461\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.9395\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.1748\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e71.06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e97.80\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Field Application of Reservoir Protection Drilling Fluid System\u003c/h2\u003e \u003cp\u003eIn 2022, the test outcomes of the aforementioned reservoir protection drilling fluid system within the Jurassic formations of the 11th Oil Production Plant are presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e as follows. The results demonstrate that in 2021, the average test production volume of the Jurassic in the 11th Oil Production Plant was 12.23 cubic meters per day. Subsequent to the drilling operations conducted with the reservoir protection drilling fluid system in 2022, the average test production volume of the Jurassic in the 11th Oil Production Plant escalated to 18.55 cubic meters per day, signifying a production increment of approximately 51.68%. Evidently, the reservoir protection efficacy during the drilling process is highly significant.\u003c/p\u003e \u003cp\u003eIn addition, the reservoir protection drilling fluid was implemented in the field for horizontal well test oil applications in both the same well group and different well groups within the Zhen 470 Block and Pengyang Block of the Jurassic in the 11th Oil Production Plant. The corresponding results are presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e. To begin with, in comparison with Tong 53-33S, Tong 52\u0026thinsp;\u0026minus;\u0026thinsp;32, and Tong 54\u0026thinsp;\u0026minus;\u0026thinsp;32 within the same well group in the Zhen 470 Block, the test oil production of the relevant well group exhibited an increment of 47.01% and 48.60% respectively. Subsequently, in the Pengyang Operating Area, the production of the horizontal well Yan 83\u0026thinsp;\u0026minus;\u0026thinsp;01 in distinct well groups was enhanced by 80.90% relative to that of Yan 90\u0026thinsp;\u0026minus;\u0026thinsp;31. Evidently, the reservoir protection effect is satisfactory, and the production enhancement effect is highly significant.\u003c/p\u003e \u003c/div\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003eIn this study, based on a comprehensive examination of the reservoir physical property characteristics and an in-depth sensitivity evaluation of the Jurassic reservoirs within the Ordos Basin, the underlying damage mechanism of the drilling fluids to the Jurassic reservoirs in Zhenbei Oilfield was elucidated. Subsequently, extensive research and experimental investigations were conducted regarding the drilling fluid technology dedicated to the protection of Jurassic reservoirs. The average porosity of the Jurassic reservoirs is approximately 15%, and the permeability exceeds 100\u0026times;10⁻\u0026sup3; \u003cem\u003e\u0026micro;\u003c/em\u003em\u0026sup2;. These reservoirs fall into the category of low-porosity and medium-permeability reservoirs. Notably, the pore structures are predominantly composed of intergranular pores and dissolution pores, accompanied by a relatively low displacement pressure. Overall, the physical properties of these reservoirs exhibit a favorable condition. The sensitivity of the Jurassic reservoirs is primarily characterized by a moderately weak to velocity-sensitive nature. In terms of the specific severity of sensitivity, it follows the order of velocity sensitivity\u0026thinsp;\u0026gt;\u0026thinsp;water sensitivity\u0026thinsp;\u0026gt;\u0026thinsp;alkali sensitivity\u0026thinsp;\u0026gt;\u0026thinsp;acid sensitivity. The formation microparticles tend to migrate within the pores along with the filtrate and subsequently accumulate in the throats, thereby inducing blockages and leading to a reduction in permeability. A sophisticated set of drilling fluid technology for the protection of Jurassic reservoirs has been successfully developed. The fluid loss under medium pressure is precisely 4.5 mL, with an average plugging rate reaching 71.06% and an average core permeability recovery rate attaining 97.80%. As the oil and gas development progresses in the later stage, the temporary plugging layer will gradually dissolve and self-degrade, thereby restoring the unobstructed state of the pores and throats and effectively fulfilling the objective of reservoir protection.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eData Availability/ Availability of Data and Materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets used and/or analyzed during the current study available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCRediT Authorship Contribution Statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eJingguang Wang\u003c/strong\u003e: Conceptualization, Funding acquisition, Investigation, Writing-review \u0026amp; editing.\u003cstrong\u003e\u0026nbsp;Wang He\u003c/strong\u003e: Writing-original draft, Writing-review \u0026amp; editing. \u003cstrong\u003eMin Zhang\u003c/strong\u003e: Methodology.\u003cstrong\u003e\u0026nbsp;Chen He\u003c/strong\u003e: Validation. \u003cstrong\u003ePeiming Shi\u003c/strong\u003e: Data curation.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of Interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that there is no conflict of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe research is not financially supported.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eSong, C., Ghanizadeh, A., Younis, A. \u0026amp; Clarkson, C. 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Sci.\u003c/em\u003e \u003cb\u003e19\u003c/b\u003e, 3149\u0026ndash;3158 (2022).\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"},{"header":"Table 5","content":"\u003cp\u003eTable 5 is available in the Supplementary Files section.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Oil and gas exploration and development, Low permeability oil and gas reservoirs, Reservoir damage mechanism, Drilling fluid system, Reservoir protection performance","lastPublishedDoi":"10.21203/rs.3.rs-6426437/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6426437/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eLow permeability oil and gas reservoirs have become increasingly prominent in China's oil and gas exploration and development and are an important area for reserve growth, and the Yanchang formation in the Ordos Basin is a low-permeability reservoir that contains abundant oil and gas resources. Jurassic reservoirs are widely distributed in the Ordos Basin, and the proportion of reservoir production has been increasing year by year. In this study, the mechanism of drilling fluid damage in Jurassic reservoirs was revealed through the analysis of physical parameters, rock characteristics, pore structure, and sensitivity. As a result, the reservoir properties are mainly intergranular pores and dissolution pores, with low displacement pressure, low porosity, and high permeability, and the overall physical properties are good. When foreign solid and liquid phases invade, it is easy to cause throat particle migration, leading to pore blockage and serious reservoir damage. Secondly, through the optimization of oil soluble temporary plugging agents and filter loss reducing agents, combined with experimental methods such as particle size analysis and scanning electron microscopy, a drilling fluid system for Jurassic reservoir protection in Zhenbei Oilfield was obtained, which includes temporary plugging agent G325 and self-degradable filter loss reducing agent. The medium pressure water loss of the drilling fluid system is 4.5 mL, with an average sealing rate of 71.06% and an average core permeability recovery rate of 97.80%. overall, the drilling fluid has excellent sealing performance and reservoir protection performance.\u003c/p\u003e","manuscriptTitle":"Research on the Damage Mechanism and Reservoir Protection Drilling Fluid System of Jurassic Reservoir in Zhenbei Oilfield","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-05-07 06:13:19","doi":"10.21203/rs.3.rs-6426437/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-07-11T11:38:39+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-06-06T11:38:06+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"300783774022978270768833939674790213301","date":"2025-06-05T11:42:59+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"125320654877842342316718836047281235062","date":"2025-06-05T02:10:21+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-05-07T14:05:26+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"37823414164011546955740452470454830328","date":"2025-04-29T10:54:52+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-04-24T08:23:40+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-04-24T08:20:37+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-04-24T07:08:27+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-04-18T00:11:28+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2025-04-18T00:10:20+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"3024f8e1-8189-4caf-a31b-ba538c6d898d","owner":[],"postedDate":"May 7th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":47632574,"name":"Physical sciences/Energy science and technology"},{"id":47632575,"name":"Physical sciences/Materials science"}],"tags":[],"updatedAt":"2026-02-09T16:00:09+00:00","versionOfRecord":{"articleIdentity":"rs-6426437","link":"https://doi.org/10.1038/s41598-026-35924-5","journal":{"identity":"scientific-reports","isVorOnly":false,"title":"Scientific Reports"},"publishedOn":"2026-02-02 15:56:57","publishedOnDateReadable":"February 2nd, 2026"},"versionCreatedAt":"2025-05-07 06:13:19","video":"","vorDoi":"10.1038/s41598-026-35924-5","vorDoiUrl":"https://doi.org/10.1038/s41598-026-35924-5","workflowStages":[]},"version":"v1","identity":"rs-6426437","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6426437","identity":"rs-6426437","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}