Dolomite Reservoir Differences in Characteristics and Controlling Factors of Grainstone Shoal facies in Qixia Formation, Sichuan Basin

Dolomite Reservoir Differences in Characteristics and Controlling Factors of Grainstone Shoal facies in Qixia Formation, Sichuan Basin | 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 Research Article Dolomite Reservoir Differences in Characteristics and Controlling Factors of Grainstone Shoal facies in Qixia Formation, Sichuan Basin Benjian Zhang, Hualing Ma, Xiaojie Huang, Xihua Zhang, Xiao Chen, and 6 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7007312/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 15 Nov, 2025 Read the published version in Carbonates and Evaporites → Version 1 posted 12 You are reading this latest preprint version Abstract The grain shoal facies dolomites of the Qixia Formation in the Sichuan Basin exhibit extensive distribution, diverse types, and significant variations in reservoir quality. Based on core observations, thin section identifications, and geochemical analysis data, this study systematically compares the characteristics of platform-margin shoal and intra-platform shoal dolomite reservoirs in the Qixia Formation. Results demonstrate that platform-margin shoal dolomites feature greater single-layer thickness (average > 5 m), stronger and more complete dolomitization (dolomite content > 85%), characterized by burial dolomitization, with developed dissolution vugs and intercrystalline pores (average porosity 2.9%). In contrast, intra-platform shoal dolomites show thinner single layers (average < 3 m), relatively lower and incomplete dolomitization (dolomite content 30%-60%), dominated by penecontemporaneous dolomitization, with reservoir spaces mainly composed of residual intergranular pores (average porosity 1.9%), exhibiting inferior physical properties compared to platform-margin shoal facies. Dolomite reservoirs with prolonged and complete dolomitization processes demonstrate better physical properties. The platform-margin shoal facies have higher energy, superior initial physical properties, and stronger fluid mobility compared to intra-platform shoal facies, providing more favorable diagenetic-reservoir forming conditions for multi-stage dolomitization. This holds significant implications for predicting favorable exploration zones of grain shoal facies dolomite reservoirs. Sichuan Basin Qixia Formation Grain shoal facies Dolomitization Dolomite reservoirs Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 1. Introduction Recent years have witnessed significant breakthroughs in natural gas exploration of the Qixia Formation in the Sichuan Basin, with discovered reservoirs primarily distributed in the Shuangyushi Structural Belt (NW Sichuan) and Gaomo Structural Belt (Central Sichuan) (Fig. 1a). Well Shuangtan-1 yielded a daily gas production of 87.6×10 4 m³, with reservoir burial depths exceeding 7,000 m, representing a typical ultra-deep carbonate reservoir (Zhang et al., 2018). Exploration practices and previous studies reveal that reservoir heterogeneity in this interval is strongly controlled by dolomitization processes and deep burial conditions. For instance, although dolomites in both western and central Sichuan originated from grain shoal facies limestones, their reservoir properties exhibit marked differences, with porosity ranging irregularly from 2–10.8% (Zhang et al., 2019; Hu et al., 2010; Zhou et al., 2016; Hou et al., 2017; Zhou et al., 2019). Studies indicate that dolomite reservoir quality is closely associated with dolomitization mechanisms (Purser et al., 1994; Braithwaite et al., 2004). However, the genesis of Qixia dolomites remains controversial (Shu et al., 2012; Yuan et al., 2019; Xu et al., 2019; Li et al., 2016a; Li et al., 2016b; Geng et al., 2024). Proposed models include penecontemporaneous dolomitization, mixed-water dolomitization, and basalt-leaching origins. Recent drilling data has also sparked debates about hydrothermal dolomitization(Hu et al., 2018; Pei et al., 2021; Zhang et al., 2015; Feng et al., 2016), yet no consensus exists regarding the dominant mechanism. The authors propose that these widely distributed, deeply buried ancient dolomites likely resulted from polygenetic and superimposed processes, with varying genetic mechanisms across different regions. Previous research demonstrates that dolomitization is not only influenced by depositional environments but also intricately linked to hydrodynamic energy, crustal uplift, and tectonic evolution (Swennen et al., 2012; Cruset et al., 2023). Therefore, this study aims to systematically investigate the differential characteristics and controlling mechanisms of grain shoal facies dolomite reservoirs in western and central Sichuan through comparative analysis of hydrodynamic regimes, depositional environments, and tectonic activities, providing scientific insights for reservoir evaluation and exploitation in the basin. 2. Geological setting The Sichuan Basin in the research area belongs to the Upper Yangtze Plate in terms of tectonic location, and developed marine carbonate deposits in the Late Paleozoic (He et al., 2011; Liu et al., 2021). The Permian Qixia Formation in the Sichuan Basin comprises a marine sedimentary succession dominated by carbonate rocks interbedded with mudstones/shales and siliceous rocks (Li et al., 2019). Stratigraphically, it can be divided into Member 1 (Q 1 x 1 ) and Member 2 (Q 1 x 2 , Fig. 1c) from bottom to top. Q 1 x 1 represents a transgressive systems tract (TST) bounded at its base by a regional uplift-related erosional unconformity (Zhou et al., 2016), whereas Q 1 x 2 constitutes a highstand systems tract (HST) capped by a local exposure-related unconformity, together forming a complete third-order sequence (Liu et al., 2021a). The deposition of the Qixia Formation occurred on a gentle paleoslope with southwest high and northeast low topography, inherited from two major tectonic uplift events: the Caledonian and Early Hercynian movements (Zhou et al., 2016). Within this gentle slope setting, the Qixia Formation predominantly developed open platform facies(Han et al., 2016). Q 1 x 1 consists mainly of micritic limestones, argillaceous micritic limestones, and bioclastic limestones. Q 1 x 2 is characterized by bioclastic limestones, leopard-spotted dolomitic limestones, massive medium-to coarse-crystalline dolomites, mottled medium- to coarse-crystalline dolomites, and brecciated dolomites (Yang et al., 2015). Previous studies demonstrate that during the depositional phase of the Qixia Formation, the western Sichuan Basin was situated within platform-margin facies (Fig. 1b), positioned between carbonate platform slopes and open platform environments (Wang et al., 2024; Han et al., 2023). This narrow topographic high faced the open marine basin near normal wave base level, characterized by: (1)high hydrodynamic energy: frequent wave agitation promoted selective removal of micritic matrix, resulting in sparite-dominated fabrics with minimal intergranular micrite; (2) evaporative settings: elevated paleotopography and shallow water depths accelerated evaporative concentration, increasing porewater salinity; (3)burial diagenesis: subsequent temperature-pressure increases during burial facilitated pervasive dolomitization, ultimately forming high-quality platform-margin dolomite reservoirs. In northwestern Sichuan Basin, dolomite reservoirs predominantly occur in platform-margin grain shoal microfacies (PMG). In contrast, the central Sichuan region developed open platform facies within intra-platform settings, located landward of the platform margin (Xu et al., 2024; Duan et al., 2021). Key depositional features include: (1) low-energy environments: situated below normal wave base with limited wave influence due to platform-margin barrier effects, favoring micrite-rich sedimentation; (2)dominant lithologies: micritic limestones, bioclastic micritic limestones, and micritic bioclastic limestones with high micrite content (> 60%)(Liu et al., 2020); (3)localized shoals: shallow bathymetry in intra-platform highs provided optimal photic conditions and normal salinity for biotic proliferation, forming intra-platform grain shoals dominated by micritic bioclastic limestones or micrite-sparite bioclastic limestones. In central Sichuan Basin, dolomite reservoirs primarily occur in intra-platform grain shoal microfacies (IPG)(Wang et al., 2013). 3. Samples and methods More than 15 wells have been drilled into the Qixia Formation in those two study areas, providing detailed well-logging data. A total of 160 samples were collected from dolostones and dolomitic limestones of the Qixia Formation, obtained from 6 cored wells within two study areas. This study conducted multi-parameter geochemical analyses on various lithologies of the Qixia Formation, utilizing dental drilling to obtain homogeneous samples. All analytical tests were performed at the CNPC Key Laboratory of Carbonate Reservoirs. The analytical instrumentation comprised: PANalytical X'Pert PRO X-ray diffractometer for crystallographic ordering determination; PANalytical Axios XRF X-ray fluorescence spectrometer for trace element and rare earth element analyses; DELTA V Advantage isotope ratio mass spectrometer for carbon-oxygen isotopic measurements; TRITON PLUS thermal ionization mass spectrometer for strontium isotopic analysis. During the carbon-oxygen isotope analysis, the McCrea phosphoric acid method was employed, where samples reacted with anhydrous phosphoric acid at 25°C for 24 hours. Measurements were calibrated against VPDB standard using GBW04405 reference material, achieving analytical precision of ± 0.1‰. X-ray diffraction (XRD) quantitative analysis was conducted using operational parameters set at 30 kV tube voltage, 10 mA tube current, 2°2θ/min scanning speed, and 4.5°2θ step width. A total 160 samples were used for creating thin sections with a thickness of 0.03 mm. Rock thin sections were stained with Alizarin Red S and examined using an Olympus BH-2 polarizing microscope. Cathodoluminescence (CL) analysis was performed on a CL8200-MK5 cathodoluminescence system coupled with an Olympus BX51 optical microscope, operating at 15 kV beam voltage, 350 µA beam current, and 0.003 mBar vacuum pressure. 4. Results 4.1 Spatial occurrence and thickness of dolomites During the early depositional stage of the Qixia Formation, the water depth was relatively greater, dominated by open platform deposits. By the middle to late stages, sea level regression triggered widespread development of platform margin deposits. Based on field outcrops, drilling lithology, and log characteristics, the formation can be subdivided into Member 1 and Member 2. In the northwestern Sichuan region, the Qixia Formation dolomite developed in the middle-lower section of Member 2, exhibiting favorable macroscopic distribution characteristics such as stratigraphic consistency, layering continuity, and stable distribution, with an average single-layer thickness exceeding 5 m (Fig. 2). Notably, it shows no features of fault-aligned distribution or flower/mushroom-shaped geometries. In contrast, the central basin area also hosts Qixia Formation dolomite within Member 2, but predominantly in the middle-upper section. Here, the dolomite layers are thinner (average single-layer thickness < 3 m) and display poorer continuity (Fig. 2). 4.2 Petrology and Sedimentology Through thin-section identification, the Qixia Formation dolomites are classified into three subtypes based on crystal size and automorphism degree: fine-crystalline dolomite, medium-crystalline dolomite, and medium-coarse-crystalline dolomite. (1) Fine-crystalline dolomite This type of dolomite is sparsely distributed in the Qixia Formation and constitutes a minor proportion of the thick dolomite strata. On fresh surfaces of core samples, it appears relatively homogeneous overall, with low porosity development (Fig. 3a). The dolomite crystals range in size from 0.1–0.25 mm, exhibit relatively poor automorphism (mostly subhedral to anhedral), and display interlocking contacts. A limited number of intercrystalline micropores are observed, resulting in a relatively dense rock texture (Fig. 3b, Fig. 3c). (2) Medium-crystalline dolomite This subtype is the most widespread among the matrix dolomites of the Qixia Formation. On fresh core surfaces, higher porosity development is evident (Fig. 3d). The dolomite crystals measure 0.2–0.5 mm (predominantly ~ 0.4 mm) and exhibit well-developed automorphism with straight crystal edges, typically forming euhedral shapes. Intercrystalline pores are highly developed, and bitumen filling is commonly observed (Fig. 3e, Fig. 3f). (3) Medium-coarse-crystalline dolomite This subtype is also widely distributed in the Qixia Formation matrix dolomites, often interbedded with medium-crystalline dolomite. Core samples reveal slightly reduced pore density compared to medium-crystalline dolomite (Fig. 3g). The dolomite crystals range from 0.5–0.8 mm, with some reaching ~ 1 mm. Relative to medium-crystalline dolomite, the crystals show slightly poorer automorphism (mostly subhedral), interlocking contacts, reduced intercrystalline pore development, and smaller pore diameters, predominantly manifesting as residual intercrystalline pores (Fig. 3h). A small amount of saddle dolomite can be seen in these samples (Fig. 3i). In contrast, the platform-margin shoal dolomites in the western Sichuan Basin are predominantly medium-coarse crystalline dolomite and medium-crystalline dolomite, whereas the central Sichuan Basin primarily comprises fine-crystalline dolomite with minor medium-crystalline dolomite and very rare medium-coarse crystalline dolomite. Furthermore, the degree of dolomitization differs significantly: some intra-platform shoal dolomites in the central Sichuan Basin exhibit higher calcite content, indicating incomplete dolomitization. 4.3 Geochemical characteristics of dolomite 4.3.1 Carbon and oxygen stable isotopes Firstly, the limestone samples from of the Qixia Formation in the western Sichuan Basin exhibit δ 13 C values ranging from 1.0 to 3.3‰ VPDB (mean 2.55 ± 0.31‰, n = 6) and δ 18 O values ranging from − 6.0 to − 7.8‰ VPDB (mean − 7.03 ± 0.24‰, n = 6; Fig. 4). The carbon isotopic values of the limestone fall within the range of values for carbonates in equilibrium with those of Permian seawater (δ 13 C = 0–5‰ VPDB; Veizer et al., 1999; Korte et al., 2005), and oxygen isotopic values are slightly lower (δ 18 O = − 2–−7‰ VPDB). Compared with the limestone (Fig. 9), the dolomites’ carbon and oxygen stable isotopes of different grain shoal facies presents two diagenetic fluids. The platform-margin shoal dolomites in the western Sichuan Basin have the same isotopic values, with δ 13 C values of 1.51 to 3.71‰ VPDB (mean 2.81 ± 0.45‰ VPDB, n = 4) and δ 18 O values of − 4.2 to − 8.1‰ VPDB (mean − 7.04 ± 0.64‰ VPDB, n = 4; Fig. 4). Meanwhile, intra-platform shoal dolomites in the central Sichuan Basin have the same isotopic values, with δ 13 C values of 4.1 to 5.4‰ VPDB (mean 4.71 ± 0.25‰ VPDB, n = 6) and δ 18 O values of − 7.8 to − 8.4‰ VPDB (mean − 8.03 ± 0.24‰ VPDB, n = 6; Fig. 4). And three samples of saddle dolomite yield lower δ 13 C values from 1.2 to 2.54‰ VPDB (mean 1.81 ± 0.23‰ VPDB) and δ 18 O values from − 8.35 to − 9.5‰ VPDB (mean − 8.88 ± 0.38‰ VPDB). Additionally, four samples of limestones in the central Sichuan Basin have higher δ 18 O values from − 5.81 to -7.7‰ VPDB (mean 6.61 ± 0.23‰ VPDB) and δ 13 C values from 4.1 to 5.05‰ VPDB (mean 4.56 ± 0.13‰ VPDB; Fig. 4). 4.3.2 Strontium stable isotopes ( 87 Sr/ 86 Sr) The 87 Sr/ 86 Sr ratio for the all samples of the Qixia Formation in the central Sichuan Basin ranges from 0.707455 to 0.708576 (Fig. 5), and meanwhile the 87 Sr/ 86 Sr ratio in the western Sichuan Basin ranges from 0.707277 to 0.709466 (Yang 2024). However, according to Veizer et al. (1999), the best estimated 87 Sr/ 86 Sr ratio of Permian seawater ranges from 0.706800 and 0.708070. Among all carbonates of the Qixia Formation in the central Sichuan Basin, the limestones have the lowest 87 Sr/ 86 Sr ratio of 0.707277 to 0.707755 (mean 0.707566 ± 0.000055, n = 2), and the dolomites have the higher 87 Sr/ 86 Sr ratio of 0.707466 to 0.708576 (mean 0.707666 ± 0.000094, n = 6). The 87 Sr/ 86 Sr ratio differences between the limestones and dolomites of the Qixia Formation in the western Sichuan Basin are the same as in the central area (Yang 2024). 4.3.3 Rare-earth elements (REEs) The REE concentrations of the studied carbonates are normalized to the REE compositions in the surface Pacific seawater (Kawabe et al., 1998), and seawater-normalized REE profiles of carbonates are presented in Fig. 6. All carbonates have a positive Eu SN anomaly (mean 5.54 ± 0.38, n = 5), and a positive Yb SN anomaly (mean 3.35 ± 0.21, n = 5; Fig. 6). However, a slight negative Ce SN anomaly (mean 0.82 ± 0.04, n = 3; Fig. 6) occurs within dolostone. 4.4 Reservoir spaces and physical property 4.4.1 Reservoir spaces The carbonate rocks of the Qixia Formation in the study area are deeply buried, where the primary pores of the limestone have been largely eliminated, with secondary pores dominating. Based on core and thin section observations, these pores can be further classified into intercrystalline pores, intercrystalline dissolution pores, dissolution vugs, and fractures. (1) Intercrystalline Pores and Intercrystalline Dissolution Pores Intercrystalline pores refer to voids between dolomite crystals formed by dolomitization. They are primarily developed in tidal flat facies fine- to medium-crystalline dolomites and medium-crystalline dolomites in the central and western parts of the basin. These pores are surrounded by well-crystallized dolomite with straight crystal boundaries, exhibiting regular shapes, clear boundaries, and diameters mostly less than 500 micrometers. Intercrystalline dissolution pores, formed by dissolution processes on the basis of intercrystalline pores, are larger in diameter than intercrystalline pores and display irregular, bay-like boundary (Fig. 7a, Fig. 7d, Fig. 7e). (2) Dissolution Vugs Secondary dissolution vugs are well-developed in the dolomites of the Qixia Formation. Based on their sizes, they can be divided into two categories. Firstly, small vugs are scattered as pinpoint pores in the core, with diameters ranging from approximately 500 to 1,000 micrometers(Fig. 7b). Secondly, medium to large vugs: These exhibit centimeter-scale diameters and are irregularly distributed in the core, indicating intense dissolution modification of the Qixia Formation. Medium to large vugs are predominantly developed in the dolomites of the Qixia Formation in the western Sichuan region. (3) Fractures Due to the high brittleness of dolomite, structural fractures are more readily developed in dolomite reservoirs. In the Qixia Formation dolomite reservoir cores from the study area, numerous microfractures can be observed. These fractures typically display straight boundaries and occur as single or multiple parallel features. In some cases, structurally enlarged dissolution fractures are observed, suggesting that post-fracture dissolution expanded the fractures into pathways for corrosive fluids. This process enhances the reservoir's permeability. Additionally, fractures are often associated with medium to large dissolution vugs (Fig. 7c, Fig. 7f). 4.4.2 Reservoir physical property The porosity and permeability of the Qixia Formation reservoirs in the Central Sichuan and Western Sichuan regions exhibit significant differences. Core samples from the Qixia Formation in the Western Sichuan region demonstrate superior matrix properties, with an average porosity of 2.9% (primary range: 2–6%, maximum: 10.8%; samples with porosity exceeding 2% show an average of 3.43%, n = 135) and an average permeability of 6.23 mD (maximum: 49.2 mD). In contrast, core samples from the Central Sichuan region display slightly lower matrix properties, with an average porosity of 1.9% (primary range: 1–4%, maximum: 8.9%; samples with porosity exceeding 2% have an average of 2.43%, n = 65) and an average permeability of 0.35 mD (maximum: 16.3 mD). This disparity highlights the distinct reservoir characteristics and diagenetic evolution between the two regions(Fig. 8). 5. Discussion 5.1 Differences of the dolomitization between the dolomites of the central and western Sichuan Basin Based on the petrographic characteristics, isotopic signatures, and rare earth element features of dolomites in the Central Sichuan and Western Sichuan regions, it is concluded that the platform-margin shoal dolomite reservoirs in the Western Sichuan region were formed by burial-stage dolomitization. These dolomites exhibit a higher degree of dolomitization, greater single-layer thickness, more euhedral dolomite crystal forms, lower δ¹³C values, and lower δ¹⁸O values (Fig. 4), consistent with the carbon and oxygen isotopic composition of Permian coeval seawater(Jones et al., 2004). This indicates that the diagenetic fluids were contemporaneous seawater entrapped during burial. However, some dolomites in the Western Sichuan region were influenced by hydrothermal dolomitization, forming saddle-shaped dolomites characterized by higher δ¹³C values and the lowest δ¹⁸O values (Fig. 3, Fig. 4), which exceed the isotopic range of coeval seawater. In contrast, the intra-platform shoal dolomite reservoirs in the Central Sichuan region originated from penecontemporaneous dolomitization. These dolomites show slightly lower degrees of dolomitization, smaller single-layer thicknesses, finer crystal sizes, higher δ¹³C values, and elevated δ¹⁸O values, reflecting the influence of meteoric freshwater. Additionally, their dolomites yield older U-Pb ages, aligning closely with the depositional period of the Qixia Formation(Pan, L et al., 2020; Zhong et al., 2014). In contrast, the platform-margin shoal dolomites in the Western Sichuan region have younger U-Pb ages (approximately Early Triassic, Fig. 9), coinciding with the early burial diagenetic stage of the Qixia Formation(Lu et al., 2024; Chen et al., 2024). 5.2 Differences of the reservoir property and controlling factors between the dolostones of the central and western Sichuan Basin Based on porosity and permeability measurements, the platform-margin shoal dolomite reservoirs in the Western Sichuan region exhibit superior physical properties compared to the intra-platform shoal dolomite reservoirs in the Central Sichuan region. In terms of reservoir space development (including pores, dissolution vugs, and fractures), the Western Sichuan dolomite reservoirs also contain more medium-to-large dissolution vugs and fractures (Fig. 7), consistent with their higher porosity and permeability values. The primary distinction between the two regions lies in the stage, type, and intensity of dolomitization, which govern the development and distribution of reservoir spaces and ultimately lead to differences in reservoir quality. Variations in dolomitization types are closely linked to sedimentary microfacies: the platform-margin shoal environment experienced stronger hydrodynamic conditions, more active fluid flow, shallower water depths, and higher salinity compared to the intra-platform shoal setting. These factors collectively favored dolomitization processes. So, the sedimentary facies accounts for the observed differences in dolomite reservoir quality between the Western and Central Sichuan regions. 6. Conclusion Based on petrographic analysis, geochemical data and reservoir characteristics, the following conclusions are drawn about the differences of dolomite reservoir property and its controlling factors between platform-margin shoal and intra-platform shoal, of the Middle Permian Qixia Formation of the Sichuan Basin. (1) In the western area of Sichuan Basin, the Qixia Formation develops pore-type dolomite reservoirs of platform-margin shoal facies, characterized by large thickness and generally high porosity. These reservoirs are dominated by medium to coarse-crystalline dolomite, with well-developed intercrystalline pores and dissolution-enlarged pores. In contrast, the central Sichuan Basin features fracture-pore type dolomite reservoirs of intra-platform shoal facies in the Qixia Formation, showing thinner thickness and more variable porosity. These reservoirs mainly consist of fine-crystalline dolomite with intercrystalline pores, accompanied by minor medium-coarse crystalline dolomite reservoirs containing both intercrystalline pores and dissolution-enlarged pores. (2) The Qixia Formation dolomite reservoirs in western Sichuan Basin developed from grain limestone formed in high-energy platform-margin shoals through multiple stages of dolomitization. The burial dolomitization during the Middle Triassic period served as the key factor in pore development. Conversely, the Qixia Formation dolomite reservoirs in central Sichuan Basin originated from wackestone or packestone in low-energy intra-platform shoals through syngenetic dolomitization. Although pore development occurred earlier in this area, the pore scale and development degree are inferior to those in western Sichuan. Both regions experienced hydrothermal dolomitization, but its contribution to reservoir quality is relatively minor. (3) The high-energy grain shoal microfacies in platform margin areas of the Qixia Formation were situated in relatively shallower positions, facilitating meteoric water leaching and dissolution during penecontemporaneous stages. This process created higher initial porosity and allowed prolonged seawater interaction within the sedimentary strata. These conditions enabled sustained and more complete dolomitization, favoring the formation of dolomite intercrystalline pores and subsequent dissolution processes, ultimately resulting in high-porosity dolomite reservoirs. Therefore, high-energy grain shoals constitute the critical controlling factor for dolomite reservoir development in the Qixia Formation. Declarations Author Contribution BJ Z and HT S wrote the main manuscript text ,and XJ H, XH Z, X C and FJ Z prepared figures 1-6.X C and R L, and W W prepared figures 6-9. All authors reviewed the manuscript References Braithwaite, C.J.R., Rizzi, G., Darke, G., 2004. The geometry and petrogenesis of dolomite hydrocarbon reservoirs. Geological Society of London, Special Publication 235, 1–6. Cruset, D., Vergés, J., Muñoz-López, D., Moragas, M., Cantarero, I., Travé, A., 2023. Fluid evolution from extension to compression in the Pyrenean Fold Belt and BasqueCantabrian Basin: a review. Earth-Science Reviews 243, 104494. Chen W, Mu C, Wang Q et al. 2024. Study on U-Pb age and provenance of detrital zircons from sandstones of the Shaximiao Formation, northwestern Sichuan Basin. Sedimentary Geology and Tethyan Geology, 44(03):613-629. Duan J, Zheng J, Shen A et al., 2021. Characteristics and genesis of dolomite reservoir of the Lower Permian Qixia Formation in central Sichuan Basin. Marine Origin Petroleum Geology, 26(04):345-356. Feng M, Qiang Z, Shen P et al., 2016. Evidences for hydrothermal dolomite of Sinian Dengying Formation in Gaoshiti-Moxi area,Sichuan Basin. Acta Petrolei Sinica. 37(05): 587-598. Ge X, Mu C, Men X, et al., 2023. Discussion on U-Pb Dating and Tectonic Setting of K- bentonites from Late Ordovician-Early Silurian Period in the Sichuan Basin. Sedimentary Geology and Tethyan Geology, 1-17. Han X, Bao Z, Xie S et al., 2016. Origin and Geochemical Characteristics of Dolomites in the Middle Permian Formation,SW Sichuan Basin,China. Earth Science. 41(01): 167-176. Han Y, Zhang J, He Z et al., 2023. Characteristics and development models of high-quality dolomite reservoirs in Middle Permian Qixia Formation, central Sichuan Basin. Natural Gas Exploration and Development, 44(01):75-88. He D, Li D, Zhang, G et al., 2011. Formation and evolution of multi-cycle superposed Sichuan Basin, China. Chinese Journal of Geology (Scientia Geologica Sinica).46(3):589-606. Hou G, Zhou J, Gu M et al., 2017. Lithofacies Paleogeography and Exploration Realms of Middle Permian Qixia Formation and Maokou Formation, Sichuan Basin. Marine Origin Petroleum Geology. 22(01): 25-31. Hu A, Pan L, Hao Y et al., 2018. Origin, Characteristics and Distribution of Dolostone Reservoir in Qixia Formation and Maokou Formation, Sichuan Basin, China. Marine Origin Petroleum Geology. 23(02): 39-52. Geng G, Chen Y, Chen K et al., 2024. Distribution and activity of strike-slip faults in Gaoshiti area of Sichuan Basin and their control and significance for the development of dolomite reservoirs in Permian Qixia Formation. Acta Petrolei Sinica, 45(12):1761-1782. Hu M, Wei G, Hu Z et al., 2010. Sequence-lithofacies palaeogeography of the Middle Permian Qixia Formation in Sichuan Basin. Journal of Palaeogeography(Chinese Edition). 12(05): 515-526. Jones, G.D., Whitaker, E.L., Smart, E.L., Sanford, W.E., 2004. Numerical analysis of seawater circulation in carbonate platforms: II. The dynamic interaction between geothermal and brine reflux circulation. American Journal of Science 304, 250–284. Keith M L, Weber J N. 1964. Carbon and oxygen isotopic composition of selected limestones and fossils. Geochimica Et Cosmochimica Acta. 28(10–11): 1787-1816. Kawabe, I., Toriumi, T., Ohta, A., Miura, N., 1998. Monoisotopic REE abundances in seawater and the origin of seawater tetrad effect. Geochemical Journal 32, 213–230. Korte, C., Jasper, T., Kozur, H.W., Veizer, J., 2005. δ18Oandδ13C of Permian brachiopods: a record of seawater evolution and continental glaciation. Palaeogeography, Palaeoclimatology, Palaeoecology. 224 (4), 333–351. Liu S, Yang Y, Deng B et al., 2021a. Tectonic evolution of the Sichuan Basin, Southwest China. Earth Science Reviews 213. Li R, Hu M, Yang W et al., 2019. Sedimentary facies model and favorable reservoir distribution of the Middle Permian in Sichuan Basin. Oil & Gas Geology, 40(02):369-379. Liu W, Zhong D, Sun H et al., 2021. Sedimentary Characteristics and Paleogeomorphic Responses of the Middle Permian Qixia Formation in the Northwestern Sichuan Basin. Acta Sedimentologica Sinica, 39(05):1275-1291. Li X，Huang S，Huang S et al., 2016a. Petrologic and geochemical characteristics and the origin of dolomites in the Qixia Formation in Nanjiang county of the Sichuan Basin. Petroleum Geology & Experiment, 38(02):251-258. Li X, Huang S, Huang K et al., 2016b. Geochemical characteristics of Middle Permian Qixia Fm dolomitized marine fluids in the Sichuan Basin. Natural Gas Industry, 36(10):35-45. Lu X, Gui L, Wang Z et al., 2024. Activity time of strike-slip faults and their controlling effects on hydrocarbon accumulation in central Sichuan Basin: evidence from U-Pb dating and fluid inclusions of cements in fault zone. Acta Petrolei Sinica, 45(04):642-658. Pan, L., Shen, A., Zhao, J., Hu, A., Hao, Y., Liang, F., Feng, Y., Wang, X., Jiang, L., 2020. LA-ICPMS U–Pb geochronology and clumped isotope constraints on the formation and evolution of an ancient dolomite reservoir: the Middle Permian of northwest Sichuan Basin (SW China). Sedimentary Geology 407, 105728. Pei S, Wang X, Li R et al., 2021. Burial dolomitization of marginal platform bank facies and its petroleum geological implications: The genesis of Middle Permian Qixia Formation dolostones in the northwestern Sichuan Basin. Natural Gas Industry, 41(04):22-29. Purser, B.H., Brown, A., Aissaoui, D.M., 1994. Nature, origin and evolution of porosity in dolomites. Special Publication International Association Sedimentologyvol. 21, pp. 283–308. Shu X, Zhang J, Li G, et al. 2012. Characteristics and Genesis of hydrothermal dolomites of Qixia and Maokou Formations in northern Sichuan Basin. Oil&Gas Geology, 33(3):442-448. Swennen, R., Dewit, J., Fierens, E., Muchez, P., Shan, M., Nader, F., Hunt, D., 2012. Multiple dolomitization events along the Pozalagua Fault (Pozalagua Quarry, BasqueCantabrian Basin, Northern Spain). Sedimentology 59, 1345–1374. Veizer, J., Ala, D., Azmy, K., Bruckschen, P., Buhl, D., Bruhn, F., Carden, G.A., Diener, A., Ebneth, S., Godderis, Y.J., 1999. 87Sr/86Sr, δ13Candδ18O evolution of Phanerozoic seawater. Chemical Geology 161 (1–3), 59–88. Wang B, Song J, Liu S et al., 2024. Types and genetic modes of dolomite in the Member 2 of Middle Permian Maokou Formation in western Sichuan Basin. Acta Petrolei Sinica, 45(12):1743-1760. Wang H, Chi Y, Zhao Z et al., 2013. Karst reservoirs developed in the Middle Permian Qixia Formation of Sichuan Basin and selection of exploration regions. Acta Petrolei Sinica. 34(05): 833-842. Xu Z. 2019. Genesis and source of gas in Middle Permian Maokou Formation of eastern Sichuan Basin. Special Oil&Gas Reservoirs, 26(2):16-22. Yang L, Gu M, Yang X et al., 2015. High-resolution Characterization of Borehole-scaled Reservoir Structure:A Case of Lower Permian Qixia Dolostone Reservoir in Well Kuang-2, Northwest of Sichuan Basin. Marine Origin Petroleum Geology, 20(04):65-72. Yang Z, Sun H, Zhong D et al., 2024. Effects of basin tectonic evolution on multi-phase dolomitization: Insights from the Middle Permian Qixia Formation of the NW Sichuan Basin, SW China. Sedimentary Geology 470(000): 18. Yuan C, Wan Y, Liu X, et al. 2019. Fine characterization of reservoir heterogeneity in the Wellblock X of Longwangmiao Formation. Special Oil&Gas Reservoirs, 26(2):121-126. Zhang B, Xie J, Yin H et al., 2018. Characteristics and exploration direction of the Middle Permian carbonate reservoirs in the Longmenshan mountain areas, western Sichuan Basin. Natural Gas Industry. 38(02): 33-42. Zhang B, Fang J, Yin H et al., 2019. A breakthrough in high-yield horizontal gas wells and great exploration and development potential in deep conventional gas reservoirs in the Sichuan Basin. Natural Gas Industry. 39(12): 1-9. Zhang T, Su Y, She G et al., 2015 A study on the genetic model of hydrothermal dolomitization in Taq Taq oilfield, Kurdistan region, Iraq—taking oilfield A in the Cretaceous in Zagros Basin as an example. Oil & Gas Geology. 36(03): 393-401. Zheng H, Yuan L, Liu B et al., 2020. Origins of Dolomitization Fluids within Middle Permian Coarse Dolomite, SW Sichuan Basin. Acta Sedimentologica Sinica, 38(03): 1-11. Zhou J, Yao G, Yang G et al., 2016. Lithofacies palaeogeography and favorable gas exploration zones of Qixia and Maokou Fms in the Sichuan Basin. Natural Gas Industry. 36(04): 8-15. Zhou J, Hao Y, Deng H et al., 2019. Genesis and distribution of vuggy dolomite reserviors of the Lower Permian Qixia Formation and Maokou Formation,western-central Sichuan Basin. Marine Origin Petroleum Geology. 24(04): 67-78. Zhong, Y., He, B., Mundil, R., Xu, Y., 2014. CA-TIMS zircon U–Pb dating of felsic ignimbrite from the Binchuan section: implications for the termination age of Emeishan large igneous province. Lithos 204, 14–19. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 15 Nov, 2025 Read the published version in Carbonates and Evaporites → Version 1 posted Editorial decision: Revision requested 09 Aug, 2025 Reviews received at journal 01 Aug, 2025 Reviews received at journal 24 Jul, 2025 Reviewers agreed at journal 21 Jul, 2025 Reviewers agreed at journal 20 Jul, 2025 Reviewers agreed at journal 20 Jul, 2025 Reviews received at journal 13 Jul, 2025 Reviewers agreed at journal 09 Jul, 2025 Reviewers invited by journal 09 Jul, 2025 Editor assigned by journal 09 Jul, 2025 Submission checks completed at journal 01 Jul, 2025 First submitted to journal 30 Jun, 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. 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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-7007312","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":484660594,"identity":"de0aad0b-1608-4d59-a28d-7d854b994b15","order_by":0,"name":"Benjian Zhang","email":"","orcid":"","institution":"PetroChina Southwest Oil and Gas Field Company","correspondingAuthor":false,"prefix":"","firstName":"Benjian","middleName":"","lastName":"Zhang","suffix":""},{"id":484660595,"identity":"37e4089f-ac71-475f-9135-ed150ba78d78","order_by":1,"name":"Hualing Ma","email":"","orcid":"","institution":"PetroChina Southwest Oil and Gas Field Company","correspondingAuthor":false,"prefix":"","firstName":"Hualing","middleName":"","lastName":"Ma","suffix":""},{"id":484660596,"identity":"75bf4e68-5a45-40d8-bce5-60580e796c5a","order_by":2,"name":"Xiaojie Huang","email":"","orcid":"","institution":"China University of Petroleum (Beijing)","correspondingAuthor":false,"prefix":"","firstName":"Xiaojie","middleName":"","lastName":"Huang","suffix":""},{"id":484660597,"identity":"1946dcb2-38f4-4a0e-8644-6f6e53786e2d","order_by":3,"name":"Xihua Zhang","email":"","orcid":"","institution":"PetroChina Southwest Oil and Gas Field Company","correspondingAuthor":false,"prefix":"","firstName":"Xihua","middleName":"","lastName":"Zhang","suffix":""},{"id":484660598,"identity":"0b605d7e-6509-4dae-ab06-a0a3b0305324","order_by":4,"name":"Xiao Chen","email":"","orcid":"","institution":"PetroChina Southwest Oil and Gas Field Company","correspondingAuthor":false,"prefix":"","firstName":"Xiao","middleName":"","lastName":"Chen","suffix":""},{"id":484660599,"identity":"ceb597cb-1cc1-460d-8992-b403ad9e5aab","order_by":5,"name":"Fujie Jiang","email":"","orcid":"","institution":"China University of Petroleum (Beijing)","correspondingAuthor":false,"prefix":"","firstName":"Fujie","middleName":"","lastName":"Jiang","suffix":""},{"id":484660600,"identity":"ced16dcf-346e-4a49-979e-3cdb2a52b7d2","order_by":6,"name":"Chen Xie","email":"","orcid":"","institution":"PetroChina Southwest Oil and Gas Field Company","correspondingAuthor":false,"prefix":"","firstName":"Chen","middleName":"","lastName":"Xie","suffix":""},{"id":484660601,"identity":"03da17ff-3683-4791-bbfa-7e663df8b803","order_by":7,"name":"Yangui Chen","email":"","orcid":"","institution":"PetroChina Southwest Oil and Gas Field Company","correspondingAuthor":false,"prefix":"","firstName":"Yangui","middleName":"","lastName":"Chen","suffix":""},{"id":484660602,"identity":"a561e5a8-78e9-4a5f-946f-5aba31b3363f","order_by":8,"name":"Ran Liu","email":"","orcid":"","institution":"PetroChina Southwest Oil and Gas Field Company","correspondingAuthor":false,"prefix":"","firstName":"Ran","middleName":"","lastName":"Liu","suffix":""},{"id":484660603,"identity":"5d23379b-8fe3-4a68-a4fe-67639bc05ece","order_by":9,"name":"Wei Wang","email":"","orcid":"","institution":"PetroChina Southwest Oil and Gas Field Company","correspondingAuthor":false,"prefix":"","firstName":"Wei","middleName":"","lastName":"Wang","suffix":""},{"id":484660604,"identity":"db5e1495-f296-4716-a008-761feb413dcc","order_by":10,"name":"Haitao Sun","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA5ElEQVRIiWNgGAWjYBACAwbGBiiT+QCEPkBYSyNUD1sCsVrg1vAYEKfFnP1w+4MfFQz2Brd7Pn7m3cEgx3cjgfFzAR4tlj2JjY09ZxgSN9w5u1ma9wyDseSNBGbpGfgcdiCxsYG3jSHB4EbuNmYgI3HDjQQ2Zh58Ws4/bGz82wZ02I2cZyAt9YS13EhsbAaqZNxwI4eNGWIdQS0PG2fLnJFInHkjzVhy7hkJw5lnHjZL43dY+oOPbyps7PluJD/88HaHjTzf8eSDn/FpgQIJCMXYIMGAiCiiAEmKR8EoGAWjYMQAALNxT1xu3dfQAAAAAElFTkSuQmCC","orcid":"","institution":"China University of Petroleum (Beijing)","correspondingAuthor":true,"prefix":"","firstName":"Haitao","middleName":"","lastName":"Sun","suffix":""}],"badges":[],"createdAt":"2025-06-30 07:08:36","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7007312/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7007312/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s13146-025-01192-z","type":"published","date":"2025-11-15T15:56:59+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":86725916,"identity":"496b552c-e4fd-4168-bfec-a469a67bd348","added_by":"auto","created_at":"2025-07-15 02:46:43","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":445958,"visible":true,"origin":"","legend":"\u003cp\u003eDistribution map of the study area and the outcrops with sedimentary facies.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-7007312/v1/48d91ea46ceced644ce944a3.png"},{"id":86725706,"identity":"8c517e2d-eee2-401d-866a-1312f508d570","added_by":"auto","created_at":"2025-07-15 02:38:42","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":333559,"visible":true,"origin":"","legend":"\u003cp\u003eDistribution map of the study area and the outcrops with sedimentary facies.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-7007312/v1/16c2569ecb3980adda513f30.png"},{"id":86725712,"identity":"d668419c-0ccd-4407-bf00-14bd7c394cb4","added_by":"auto","created_at":"2025-07-15 02:38:42","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":5913226,"visible":true,"origin":"","legend":"\u003cp\u003eDistribution map of the study area and the outcrops with sedimentary facies.\u003c/p\u003e\n\u003cp\u003ea. J45, 2897m, fine-crystalline dolomite; b. MX117, 4608.79m, fine-crystalline dolomite; c.MX117, 4602.4m, fine-crystalline dolomite; d. HJL, medium-crystalline dolomite; e. ST3, 7458m, medium-crystalline dolomite; f.MX108, 4608.79m, medium-crystalline dolomite; g. MX42, 4656.4m, coarse-crystalline dolomite with bitumen; h. MX42, 4653.46m，medium to coarse crystalline dolomite; i. SY132, 7591m, saddle dolomite.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-7007312/v1/4e98fd42d8822256f27ec3c0.png"},{"id":86725709,"identity":"dd2ca0a7-33d3-4bae-89dc-e88203ea789c","added_by":"auto","created_at":"2025-07-15 02:38:42","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":188902,"visible":true,"origin":"","legend":"\u003cp\u003eDistribution map of the study area and the outcrops with sedimentary facies.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-7007312/v1/33c268376d3529d80df63da1.png"},{"id":86725729,"identity":"e0a519b7-46e8-4771-a1af-9fb0627bbf1b","added_by":"auto","created_at":"2025-07-15 02:38:43","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":95667,"visible":true,"origin":"","legend":"\u003cp\u003e\u003csup\u003e87\u003c/sup\u003eSr/\u003csup\u003e86\u003c/sup\u003eSr ratios of different types of carbonates including limestone and dolomites of the Qixia Formation in the central Sichuan Basin.\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-7007312/v1/1c77da7a8c055476997ba0d9.png"},{"id":86725719,"identity":"29e87157-a2d3-4f81-8508-c58574a9992a","added_by":"auto","created_at":"2025-07-15 02:38:43","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":122777,"visible":true,"origin":"","legend":"\u003cp\u003eThe surface Pacific seawater normalized REE (REE\u003csub\u003eSN\u003c/sub\u003e) patterns of limestones and dolostones from the Qixia Formation in the central Sichuan Basin.\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-7007312/v1/312cb411de2f7f8802288be7.png"},{"id":86725732,"identity":"59665b9b-099f-417c-8859-81a803ce432c","added_by":"auto","created_at":"2025-07-15 02:38:44","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":3718507,"visible":true,"origin":"","legend":"\u003cp\u003eThe pores, vugs and fractures of dolostones from the Qixia Formation in the central and western Sichuan Basin.\u003c/p\u003e\n\u003cp\u003ea. ST12, 7081.4m, medium-crystalline dolomite; b. ST9, 47711.57m, dissolution vugs in the core; c.MX108, 4689.55m, tectonic fractures in the core; d. MX108, 4608.79m, intercrystalline dissolution pores; e. ST3, 7458.47m, intercrystalline pores ; f. ST102, 7679.87m, tectonic fractures in the thin section.\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-7007312/v1/5cffae0011480f6875b501ab.png"},{"id":86725715,"identity":"8cb1500a-361a-4d77-8759-e93c36697d0a","added_by":"auto","created_at":"2025-07-15 02:38:43","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":5713,"visible":true,"origin":"","legend":"\u003cp\u003eThe porosity and permeability histogram of dolostones from the Qixia Formation in the central and western Sichuan Basin.\u003c/p\u003e","description":"","filename":"placeholderimage.png","url":"https://assets-eu.researchsquare.com/files/rs-7007312/v1/31abbc15901a075494112ed4.png"},{"id":86725713,"identity":"10e6c1c2-a509-4eef-b56a-ac4262bae3f3","added_by":"auto","created_at":"2025-07-15 02:38:42","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":289879,"visible":true,"origin":"","legend":"\u003cp\u003eThe dolomite U-Pb ages of the Qixia Formation in the central and western Sichuan Basin.\u003c/p\u003e","description":"","filename":"floatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-7007312/v1/13db30c4145924e71b28714f.png"},{"id":96104942,"identity":"b5d1cf7e-c6db-46ee-828a-7cc713180150","added_by":"auto","created_at":"2025-11-17 16:01:53","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":14490696,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7007312/v1/90ecdf17-a5b2-47d2-be3a-99add1a499c1.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Dolomite Reservoir Differences in Characteristics and Controlling Factors of Grainstone Shoal facies in Qixia Formation, Sichuan Basin","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eRecent years have witnessed significant breakthroughs in natural gas exploration of the Qixia Formation in the Sichuan Basin, with discovered reservoirs primarily distributed in the Shuangyushi Structural Belt (NW Sichuan) and Gaomo Structural Belt (Central Sichuan) (Fig.\u0026nbsp;1a). Well Shuangtan-1 yielded a daily gas production of 87.6\u0026times;10\u003csup\u003e4\u003c/sup\u003e m\u0026sup3;, with reservoir burial depths exceeding 7,000 m, representing a typical ultra-deep carbonate reservoir (Zhang et al., 2018). Exploration practices and previous studies reveal that reservoir heterogeneity in this interval is strongly controlled by dolomitization processes and deep burial conditions. For instance, although dolomites in both western and central Sichuan originated from grain shoal facies limestones, their reservoir properties exhibit marked differences, with porosity ranging irregularly from 2\u0026ndash;10.8% (Zhang et al., 2019; Hu et al., 2010; Zhou et al., 2016; Hou et al., 2017; Zhou et al., 2019).\u003c/p\u003e\u003cp\u003eStudies indicate that dolomite reservoir quality is closely associated with dolomitization mechanisms (Purser et al., 1994; Braithwaite et al., 2004). However, the genesis of Qixia dolomites remains controversial (Shu et al., 2012; Yuan et al., 2019; Xu et al., 2019; Li et al., 2016a; Li et al., 2016b; Geng et al., 2024). Proposed models include penecontemporaneous dolomitization, mixed-water dolomitization, and basalt-leaching origins. Recent drilling data has also sparked debates about hydrothermal dolomitization(Hu et al., 2018; Pei et al., 2021; Zhang et al., 2015; Feng et al., 2016), yet no consensus exists regarding the dominant mechanism. The authors propose that these widely distributed, deeply buried ancient dolomites likely resulted from polygenetic and superimposed processes, with varying genetic mechanisms across different regions. Previous research demonstrates that dolomitization is not only influenced by depositional environments but also intricately linked to hydrodynamic energy, crustal uplift, and tectonic evolution (Swennen et al., 2012; Cruset et al., 2023).\u003c/p\u003e\u003cp\u003eTherefore, this study aims to systematically investigate the differential characteristics and controlling mechanisms of grain shoal facies dolomite reservoirs in western and central Sichuan through comparative analysis of hydrodynamic regimes, depositional environments, and tectonic activities, providing scientific insights for reservoir evaluation and exploitation in the basin.\u003c/p\u003e"},{"header":"2. Geological setting","content":"\u003cp\u003eThe Sichuan Basin in the research area belongs to the Upper Yangtze Plate in terms of tectonic location, and developed marine carbonate deposits in the Late Paleozoic (He et al., 2011; Liu et al., 2021). The Permian Qixia Formation in the Sichuan Basin comprises a marine sedimentary succession dominated by carbonate rocks interbedded with mudstones/shales and siliceous rocks (Li et al., 2019). Stratigraphically, it can be divided into Member 1 (Q\u003csub\u003e1\u003c/sub\u003ex\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e) and Member 2 (Q\u003csub\u003e1\u003c/sub\u003ex\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e, Fig.\u0026nbsp;1c) from bottom to top. Q\u003csub\u003e1\u003c/sub\u003ex\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e represents a transgressive systems tract (TST) bounded at its base by a regional uplift-related erosional unconformity (Zhou et al., 2016), whereas Q\u003csub\u003e1\u003c/sub\u003ex\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e constitutes a highstand systems tract (HST) capped by a local exposure-related unconformity, together forming a complete third-order sequence (Liu et al., 2021a). The deposition of the Qixia Formation occurred on a gentle paleoslope with southwest high and northeast low topography, inherited from two major tectonic uplift events: the Caledonian and Early Hercynian movements (Zhou et al., 2016). Within this gentle slope setting, the Qixia Formation predominantly developed open platform facies(Han et al., 2016). Q\u003csub\u003e1\u003c/sub\u003ex\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e consists mainly of micritic limestones, argillaceous micritic limestones, and bioclastic limestones. Q\u003csub\u003e1\u003c/sub\u003ex\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e is characterized by bioclastic limestones, leopard-spotted dolomitic limestones, massive medium-to coarse-crystalline dolomites, mottled medium- to coarse-crystalline dolomites, and brecciated dolomites (Yang et al., 2015).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003ePrevious studies demonstrate that during the depositional phase of the Qixia Formation, the western Sichuan Basin was situated within platform-margin facies (Fig.\u0026nbsp;1b), positioned between carbonate platform slopes and open platform environments (Wang et al., 2024; Han et al., 2023). This narrow topographic high faced the open marine basin near normal wave base level, characterized by: (1)high hydrodynamic energy: frequent wave agitation promoted selective removal of micritic matrix, resulting in sparite-dominated fabrics with minimal intergranular micrite; (2) evaporative settings: elevated paleotopography and shallow water depths accelerated evaporative concentration, increasing porewater salinity; (3)burial diagenesis: subsequent temperature-pressure increases during burial facilitated pervasive dolomitization, ultimately forming high-quality platform-margin dolomite reservoirs. In northwestern Sichuan Basin, dolomite reservoirs predominantly occur in platform-margin grain shoal microfacies (PMG).\u003c/p\u003e\u003cp\u003eIn contrast, the central Sichuan region developed open platform facies within intra-platform settings, located landward of the platform margin (Xu et al., 2024; Duan et al., 2021). Key depositional features include: (1) low-energy environments: situated below normal wave base with limited wave influence due to platform-margin barrier effects, favoring micrite-rich sedimentation; (2)dominant lithologies: micritic limestones, bioclastic micritic limestones, and micritic bioclastic limestones with high micrite content (\u0026gt;\u0026thinsp;60%)(Liu et al., 2020); (3)localized shoals: shallow bathymetry in intra-platform highs provided optimal photic conditions and normal salinity for biotic proliferation, forming intra-platform grain shoals dominated by micritic bioclastic limestones or micrite-sparite bioclastic limestones. In central Sichuan Basin, dolomite reservoirs primarily occur in intra-platform grain shoal microfacies (IPG)(Wang et al., 2013).\u003c/p\u003e"},{"header":"3. Samples and methods","content":"\u003cp\u003eMore than 15 wells have been drilled into the Qixia Formation in those two study areas, providing detailed well-logging data. A total of 160 samples were collected from dolostones and dolomitic limestones of the Qixia Formation, obtained from 6 cored wells within two study areas.\u003c/p\u003e\u003cp\u003eThis study conducted multi-parameter geochemical analyses on various lithologies of the Qixia Formation, utilizing dental drilling to obtain homogeneous samples. All analytical tests were performed at the CNPC Key Laboratory of Carbonate Reservoirs. The analytical instrumentation comprised: PANalytical X'Pert PRO X-ray diffractometer for crystallographic ordering determination; PANalytical Axios XRF X-ray fluorescence spectrometer for trace element and rare earth element analyses; DELTA V Advantage isotope ratio mass spectrometer for carbon-oxygen isotopic measurements; TRITON PLUS thermal ionization mass spectrometer for strontium isotopic analysis.\u003c/p\u003e\u003cp\u003eDuring the carbon-oxygen isotope analysis, the McCrea phosphoric acid method was employed, where samples reacted with anhydrous phosphoric acid at 25\u0026deg;C for 24 hours. Measurements were calibrated against VPDB standard using GBW04405 reference material, achieving analytical precision of \u0026plusmn;\u0026thinsp;0.1\u0026permil;. X-ray diffraction (XRD) quantitative analysis was conducted using operational parameters set at 30 kV tube voltage, 10 mA tube current, 2\u0026deg;2θ/min scanning speed, and 4.5\u0026deg;2θ step width. A total 160 samples were used for creating thin sections with a thickness of 0.03 mm. Rock thin sections were stained with Alizarin Red S and examined using an Olympus BH-2 polarizing microscope. Cathodoluminescence (CL) analysis was performed on a CL8200-MK5 cathodoluminescence system coupled with an Olympus BX51 optical microscope, operating at 15 kV beam voltage, 350 \u0026micro;A beam current, and 0.003 mBar vacuum pressure.\u003c/p\u003e"},{"header":"4. Results","content":"\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\n \u003ch2\u003e4.1 Spatial occurrence and thickness of dolomites\u003c/h2\u003e\n \u003cp\u003eDuring the early depositional stage of the Qixia Formation, the water depth was relatively greater, dominated by open platform deposits. By the middle to late stages, sea level regression triggered widespread development of platform margin deposits. Based on field outcrops, drilling lithology, and log characteristics, the formation can be subdivided into Member 1 and Member 2. In the northwestern Sichuan region, the Qixia Formation dolomite developed in the middle-lower section of Member 2, exhibiting favorable macroscopic distribution characteristics such as stratigraphic consistency, layering continuity, and stable distribution, with an average single-layer thickness exceeding 5 m (Fig. 2). Notably, it shows no features of fault-aligned distribution or flower/mushroom-shaped geometries. In contrast, the central basin area also hosts Qixia Formation dolomite within Member 2, but predominantly in the middle-upper section. Here, the dolomite layers are thinner (average single-layer thickness\u0026thinsp;\u0026lt;\u0026thinsp;3 m) and display poorer continuity (Fig. 2).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\n \u003ch2\u003e4.2 Petrology and Sedimentology\u003c/h2\u003e\n \u003cp\u003eThrough thin-section identification, the Qixia Formation dolomites are classified into three subtypes based on crystal size and automorphism degree: fine-crystalline dolomite, medium-crystalline dolomite, and medium-coarse-crystalline dolomite.\u003c/p\u003e\n \u003cp\u003e(1) Fine-crystalline dolomite\u003c/p\u003e\n \u003cp\u003eThis type of dolomite is sparsely distributed in the Qixia Formation and constitutes a minor proportion of the thick dolomite strata. On fresh surfaces of core samples, it appears relatively homogeneous overall, with low porosity development (Fig.\u0026nbsp;3a). The dolomite crystals range in size from 0.1\u0026ndash;0.25 mm, exhibit relatively poor automorphism (mostly subhedral to anhedral), and display interlocking contacts. A limited number of intercrystalline micropores are observed, resulting in a relatively dense rock texture (Fig.\u0026nbsp;3b, Fig.\u0026nbsp;3c).\u003c/p\u003e\n \u003cp\u003e(2) Medium-crystalline dolomite\u003c/p\u003e\n \u003cp\u003eThis subtype is the most widespread among the matrix dolomites of the Qixia Formation. On fresh core surfaces, higher porosity development is evident (Fig.\u0026nbsp;3d). The dolomite crystals measure 0.2\u0026ndash;0.5 mm (predominantly\u0026thinsp;~\u0026thinsp;0.4 mm) and exhibit well-developed automorphism with straight crystal edges, typically forming euhedral shapes. Intercrystalline pores are highly developed, and bitumen filling is commonly observed (Fig.\u0026nbsp;3e, Fig.\u0026nbsp;3f).\u003c/p\u003e\n \u003cp\u003e(3) Medium-coarse-crystalline dolomite\u003c/p\u003e\n \u003cp\u003eThis subtype is also widely distributed in the Qixia Formation matrix dolomites, often interbedded with medium-crystalline dolomite. Core samples reveal slightly reduced pore density compared to medium-crystalline dolomite (Fig.\u0026nbsp;3g). The dolomite crystals range from 0.5\u0026ndash;0.8 mm, with some reaching\u0026thinsp;~\u0026thinsp;1 mm. Relative to medium-crystalline dolomite, the crystals show slightly poorer automorphism (mostly subhedral), interlocking contacts, reduced intercrystalline pore development, and smaller pore diameters, predominantly manifesting as residual intercrystalline pores (Fig.\u0026nbsp;3h). A small amount of saddle dolomite can be seen in these samples (Fig.\u0026nbsp;3i).\u003c/p\u003e\n \u003cp\u003eIn contrast, the platform-margin shoal dolomites in the western Sichuan Basin are predominantly medium-coarse crystalline dolomite and medium-crystalline dolomite, whereas the central Sichuan Basin primarily comprises fine-crystalline dolomite with minor medium-crystalline dolomite and very rare medium-coarse crystalline dolomite. Furthermore, the degree of dolomitization differs significantly: some intra-platform shoal dolomites in the central Sichuan Basin exhibit higher calcite content, indicating incomplete dolomitization.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\n \u003ch2\u003e4.3 Geochemical characteristics of dolomite\u003c/h2\u003e\n \u003cdiv id=\"Sec8\" class=\"Section3\"\u003e\n \u003ch2\u003e4.3.1 Carbon and oxygen stable isotopes\u003c/h2\u003e\n \u003cp\u003eFirstly, the limestone samples from of the Qixia Formation in the western Sichuan Basin exhibit \u0026delta;\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003eC values ranging from 1.0 to 3.3\u0026permil; VPDB (mean 2.55\u0026thinsp;\u0026plusmn;\u0026thinsp;0.31\u0026permil;, n\u0026thinsp;=\u0026thinsp;6) and \u0026delta;\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003eO values ranging from \u0026minus;\u0026thinsp;6.0 to \u0026minus;\u0026thinsp;7.8\u0026permil; VPDB (mean \u0026minus;\u0026thinsp;7.03\u0026thinsp;\u0026plusmn;\u0026thinsp;0.24\u0026permil;, n\u0026thinsp;=\u0026thinsp;6; Fig.\u0026nbsp;4). The carbon isotopic values of the limestone fall within the range of values for carbonates in equilibrium with those of Permian seawater (\u0026delta;\u003csup\u003e13\u003c/sup\u003eC = 0\u0026ndash;5\u0026permil; VPDB; Veizer et al., 1999; Korte et al., 2005), and oxygen isotopic values are slightly lower (\u0026delta;\u003csup\u003e18\u003c/sup\u003eO\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;2\u0026ndash;\u0026minus;7\u0026permil; VPDB).\u003c/p\u003e\n \u003cp\u003eCompared with the limestone (Fig.\u0026nbsp;9), the dolomites\u0026rsquo; carbon and oxygen stable isotopes of different grain shoal facies presents two diagenetic fluids. The platform-margin shoal dolomites in the western Sichuan Basin have the same isotopic values, with \u0026delta;\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003eC values of 1.51 to 3.71\u0026permil; VPDB (mean 2.81\u0026thinsp;\u0026plusmn;\u0026thinsp;0.45\u0026permil; VPDB, n\u0026thinsp;=\u0026thinsp;4) and \u0026delta;\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003eO values of \u0026minus;\u0026thinsp;4.2 to \u0026minus;\u0026thinsp;8.1\u0026permil; VPDB (mean \u0026minus;\u0026thinsp;7.04\u0026thinsp;\u0026plusmn;\u0026thinsp;0.64\u0026permil; VPDB, n\u0026thinsp;=\u0026thinsp;4; Fig.\u0026nbsp;4). Meanwhile, intra-platform shoal dolomites in the central Sichuan Basin have the same isotopic values, with \u0026delta;\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003eC values of 4.1 to 5.4\u0026permil; VPDB (mean 4.71\u0026thinsp;\u0026plusmn;\u0026thinsp;0.25\u0026permil; VPDB, n\u0026thinsp;=\u0026thinsp;6) and \u0026delta;\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003eO values of \u0026minus;\u0026thinsp;7.8 to \u0026minus;\u0026thinsp;8.4\u0026permil; VPDB (mean \u0026minus;\u0026thinsp;8.03\u0026thinsp;\u0026plusmn;\u0026thinsp;0.24\u0026permil; VPDB, n\u0026thinsp;=\u0026thinsp;6; Fig.\u0026nbsp;4). And three samples of saddle dolomite yield lower \u0026delta;\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003eC values from 1.2 to 2.54\u0026permil; VPDB (mean 1.81\u0026thinsp;\u0026plusmn;\u0026thinsp;0.23\u0026permil; VPDB) and \u0026delta;\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003eO values from \u0026minus;\u0026thinsp;8.35 to \u0026minus;\u0026thinsp;9.5\u0026permil; VPDB (mean \u0026minus;\u0026thinsp;8.88\u0026thinsp;\u0026plusmn;\u0026thinsp;0.38\u0026permil; VPDB). Additionally, four samples of limestones in the central Sichuan Basin have higher \u0026delta;\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003eO values from \u0026minus;\u0026thinsp;5.81 to -7.7\u0026permil; VPDB (mean 6.61\u0026thinsp;\u0026plusmn;\u0026thinsp;0.23\u0026permil; VPDB) and \u0026delta;\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003eC values from 4.1 to 5.05\u0026permil; VPDB (mean 4.56\u0026thinsp;\u0026plusmn;\u0026thinsp;0.13\u0026permil; VPDB; Fig. 4).\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec9\" class=\"Section3\"\u003e\n \u003ch2\u003e4.3.2 Strontium stable isotopes (\u003csup\u003e87\u003c/sup\u003eSr/\u003csup\u003e86\u003c/sup\u003eSr)\u003c/h2\u003e\n \u003cp\u003eThe \u003csup\u003e87\u003c/sup\u003eSr/\u003csup\u003e86\u003c/sup\u003eSr ratio for the all samples of the Qixia Formation in the central Sichuan Basin ranges from 0.707455 to 0.708576 (Fig. 5), and meanwhile the \u003csup\u003e87\u003c/sup\u003eSr/\u003csup\u003e86\u003c/sup\u003eSr ratio in the western Sichuan Basin ranges from 0.707277 to 0.709466 (Yang 2024). However, according to Veizer et al. (1999), the best estimated \u003csup\u003e87\u003c/sup\u003eSr/\u003csup\u003e86\u003c/sup\u003eSr ratio of Permian seawater ranges from 0.706800 and 0.708070. Among all carbonates of the Qixia Formation in the central Sichuan Basin, the limestones have the lowest \u003csup\u003e87\u003c/sup\u003eSr/\u003csup\u003e86\u003c/sup\u003eSr ratio of 0.707277 to 0.707755 (mean 0.707566\u0026thinsp;\u0026plusmn;\u0026thinsp;0.000055, n\u0026thinsp;=\u0026thinsp;2), and the dolomites have the higher \u003csup\u003e87\u003c/sup\u003eSr/\u003csup\u003e86\u003c/sup\u003eSr ratio of 0.707466 to 0.708576 (mean 0.707666\u0026thinsp;\u0026plusmn;\u0026thinsp;0.000094, n\u0026thinsp;=\u0026thinsp;6). The \u003csup\u003e87\u003c/sup\u003eSr/\u003csup\u003e86\u003c/sup\u003eSr ratio differences between the limestones and dolomites of the Qixia Formation in the western Sichuan Basin are the same as in the central area (Yang 2024).\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec10\" class=\"Section3\"\u003e\n \u003ch2\u003e4.3.3 Rare-earth elements (REEs)\u003c/h2\u003e\n \u003cp\u003eThe REE concentrations of the studied carbonates are normalized to the REE compositions in the surface Pacific seawater (Kawabe et al., 1998), and seawater-normalized REE profiles of carbonates are presented in Fig.\u0026nbsp;6. All carbonates have a positive Eu\u003csub\u003eSN\u003c/sub\u003e anomaly (mean 5.54\u0026thinsp;\u0026plusmn;\u0026thinsp;0.38, n\u0026thinsp;=\u0026thinsp;5), and a positive Yb\u003csub\u003eSN\u003c/sub\u003e anomaly (mean 3.35\u0026thinsp;\u0026plusmn;\u0026thinsp;0.21, n\u0026thinsp;=\u0026thinsp;5; Fig. 6). However, a slight negative Ce\u003csub\u003eSN\u003c/sub\u003e anomaly (mean 0.82\u0026thinsp;\u0026plusmn;\u0026thinsp;0.04, n\u0026thinsp;=\u0026thinsp;3; Fig. 6) occurs within dolostone.\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\n \u003ch2\u003e4.4 Reservoir spaces and physical property\u003c/h2\u003e\n \u003cdiv id=\"Sec12\" class=\"Section3\"\u003e\n \u003ch2\u003e4.4.1 Reservoir spaces\u003c/h2\u003e\n \u003cp\u003eThe carbonate rocks of the Qixia Formation in the study area are deeply buried, where the primary pores of the limestone have been largely eliminated, with secondary pores dominating. Based on core and thin section observations, these pores can be further classified into intercrystalline pores, intercrystalline dissolution pores, dissolution vugs, and fractures.\u003c/p\u003e\n \u003cp\u003e(1) Intercrystalline Pores and Intercrystalline Dissolution Pores\u003c/p\u003e\n \u003cp\u003eIntercrystalline pores refer to voids between dolomite crystals formed by dolomitization. They are primarily developed in tidal flat facies fine- to medium-crystalline dolomites and medium-crystalline dolomites in the central and western parts of the basin. These pores are surrounded by well-crystallized dolomite with straight crystal boundaries, exhibiting regular shapes, clear boundaries, and diameters mostly less than 500 micrometers. Intercrystalline dissolution pores, formed by dissolution processes on the basis of intercrystalline pores, are larger in diameter than intercrystalline pores and display irregular, bay-like boundary (Fig.\u0026nbsp;7a, Fig.\u0026nbsp;7d, Fig.\u0026nbsp;7e).\u003c/p\u003e\n \u003cp\u003e(2) Dissolution Vugs\u003c/p\u003e\n \u003cp\u003eSecondary dissolution vugs are well-developed in the dolomites of the Qixia Formation. Based on their sizes, they can be divided into two categories. Firstly, small vugs are scattered as pinpoint pores in the core, with diameters ranging from approximately 500 to 1,000 micrometers(Fig.\u0026nbsp;7b). Secondly, medium to large vugs: These exhibit centimeter-scale diameters and are irregularly distributed in the core, indicating intense dissolution modification of the Qixia Formation. Medium to large vugs are predominantly developed in the dolomites of the Qixia Formation in the western Sichuan region.\u003c/p\u003e\n \u003cp\u003e(3) Fractures\u003c/p\u003e\n \u003cp\u003eDue to the high brittleness of dolomite, structural fractures are more readily developed in dolomite reservoirs. In the Qixia Formation dolomite reservoir cores from the study area, numerous microfractures can be observed. These fractures typically display straight boundaries and occur as single or multiple parallel features. In some cases, structurally enlarged dissolution fractures are observed, suggesting that post-fracture dissolution expanded the fractures into pathways for corrosive fluids. This process enhances the reservoir\u0026apos;s permeability. Additionally, fractures are often associated with medium to large dissolution vugs (Fig. 7c, Fig. 7f).\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec13\" class=\"Section3\"\u003e\n \u003ch2\u003e4.4.2 Reservoir physical property\u003c/h2\u003e\n \u003cp\u003eThe porosity and permeability of the Qixia Formation reservoirs in the Central Sichuan and Western Sichuan regions exhibit significant differences. Core samples from the Qixia Formation in the Western Sichuan region demonstrate superior matrix properties, with an average porosity of 2.9% (primary range: 2\u0026ndash;6%, maximum: 10.8%; samples with porosity exceeding 2% show an average of 3.43%, \u003cem\u003en\u003c/em\u003e\u0026thinsp;=\u0026thinsp;135) and an average permeability of 6.23 mD (maximum: 49.2 mD). In contrast, core samples from the Central Sichuan region display slightly lower matrix properties, with an average porosity of 1.9% (primary range: 1\u0026ndash;4%, maximum: 8.9%; samples with porosity exceeding 2% have an average of 2.43%, \u003cem\u003en\u003c/em\u003e\u0026thinsp;=\u0026thinsp;65) and an average permeability of 0.35 mD (maximum: 16.3 mD). This disparity highlights the distinct reservoir characteristics and diagenetic evolution between the two regions(Fig. 8).\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e"},{"header":"5. Discussion","content":"\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\u003ch2\u003e5.1 Differences of the dolomitization between the dolomites of the central and western Sichuan Basin\u003c/h2\u003e\u003cp\u003eBased on the petrographic characteristics, isotopic signatures, and rare earth element features of dolomites in the Central Sichuan and Western Sichuan regions, it is concluded that the platform-margin shoal dolomite reservoirs in the Western Sichuan region were formed by burial-stage dolomitization. These dolomites exhibit a higher degree of dolomitization, greater single-layer thickness, more euhedral dolomite crystal forms, lower δ\u0026sup1;\u0026sup3;C values, and lower δ\u0026sup1;⁸O values (Fig.\u0026nbsp;4), consistent with the carbon and oxygen isotopic composition of Permian coeval seawater(Jones et al., 2004). This indicates that the diagenetic fluids were contemporaneous seawater entrapped during burial. However, some dolomites in the Western Sichuan region were influenced by hydrothermal dolomitization, forming saddle-shaped dolomites characterized by higher δ\u0026sup1;\u0026sup3;C values and the lowest δ\u0026sup1;⁸O values (Fig.\u0026nbsp;3, Fig.\u0026nbsp;4), which exceed the isotopic range of coeval seawater. In contrast, the intra-platform shoal dolomite reservoirs in the Central Sichuan region originated from penecontemporaneous dolomitization. These dolomites show slightly lower degrees of dolomitization, smaller single-layer thicknesses, finer crystal sizes, higher δ\u0026sup1;\u0026sup3;C values, and elevated δ\u0026sup1;⁸O values, reflecting the influence of meteoric freshwater. Additionally, their dolomites yield older U-Pb ages, aligning closely with the depositional period of the Qixia Formation(Pan, L et al., 2020; Zhong et al., 2014). In contrast, the platform-margin shoal dolomites in the Western Sichuan region have younger U-Pb ages (approximately Early Triassic, Fig.\u0026nbsp;9), coinciding with the early burial diagenetic stage of the Qixia Formation(Lu et al., 2024; Chen et al., 2024).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003e5.2 Differences of the reservoir property and controlling factors between the dolostones of the central and western Sichuan Basin\u003c/b\u003e\u003c/p\u003e\u003cp\u003eBased on porosity and permeability measurements, the platform-margin shoal dolomite reservoirs in the Western Sichuan region exhibit superior physical properties compared to the intra-platform shoal dolomite reservoirs in the Central Sichuan region. In terms of reservoir space development (including pores, dissolution vugs, and fractures), the Western Sichuan dolomite reservoirs also contain more medium-to-large dissolution vugs and fractures (Fig.\u0026nbsp;7), consistent with their higher porosity and permeability values. The primary distinction between the two regions lies in the stage, type, and intensity of dolomitization, which govern the development and distribution of reservoir spaces and ultimately lead to differences in reservoir quality. Variations in dolomitization types are closely linked to sedimentary microfacies: the platform-margin shoal environment experienced stronger hydrodynamic conditions, more active fluid flow, shallower water depths, and higher salinity compared to the intra-platform shoal setting. These factors collectively favored dolomitization processes. So, the sedimentary facies accounts for the observed differences in dolomite reservoir quality between the Western and Central Sichuan regions.\u003c/p\u003e\u003c/div\u003e"},{"header":"6. Conclusion","content":"\u003cp\u003eBased on petrographic analysis, geochemical data and reservoir characteristics, the following conclusions are drawn about the differences of dolomite reservoir property and its controlling factors between platform-margin shoal and intra-platform shoal, of the Middle Permian Qixia Formation of the Sichuan Basin.\u003c/p\u003e\u003cp\u003e(1) In the western area of Sichuan Basin, the Qixia Formation develops pore-type dolomite reservoirs of platform-margin shoal facies, characterized by large thickness and generally high porosity. These reservoirs are dominated by medium to coarse-crystalline dolomite, with well-developed intercrystalline pores and dissolution-enlarged pores. In contrast, the central Sichuan Basin features fracture-pore type dolomite reservoirs of intra-platform shoal facies in the Qixia Formation, showing thinner thickness and more variable porosity. These reservoirs mainly consist of fine-crystalline dolomite with intercrystalline pores, accompanied by minor medium-coarse crystalline dolomite reservoirs containing both intercrystalline pores and dissolution-enlarged pores.\u003c/p\u003e\u003cp\u003e(2) The Qixia Formation dolomite reservoirs in western Sichuan Basin developed from grain limestone formed in high-energy platform-margin shoals through multiple stages of dolomitization. The burial dolomitization during the Middle Triassic period served as the key factor in pore development. Conversely, the Qixia Formation dolomite reservoirs in central Sichuan Basin originated from wackestone or packestone in low-energy intra-platform shoals through syngenetic dolomitization. Although pore development occurred earlier in this area, the pore scale and development degree are inferior to those in western Sichuan. Both regions experienced hydrothermal dolomitization, but its contribution to reservoir quality is relatively minor.\u003c/p\u003e\u003cp\u003e(3) The high-energy grain shoal microfacies in platform margin areas of the Qixia Formation were situated in relatively shallower positions, facilitating meteoric water leaching and dissolution during penecontemporaneous stages. This process created higher initial porosity and allowed prolonged seawater interaction within the sedimentary strata. These conditions enabled sustained and more complete dolomitization, favoring the formation of dolomite intercrystalline pores and subsequent dissolution processes, ultimately resulting in high-porosity dolomite reservoirs. Therefore, high-energy grain shoals constitute the critical controlling factor for dolomite reservoir development in the Qixia Formation.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eBJ Z and HT S wrote the main manuscript text ,and XJ H, XH Z, X C and FJ Z prepared figures 1-6.X C and R L, and W W prepared figures 6-9. All authors reviewed the manuscript\u003c/p\u003e"},{"header":"References","content":"\u003col class=\"decimal_type\"\u003e\n \u003cli\u003eBraithwaite, C.J.R., Rizzi, G., Darke, G., 2004. The geometry and petrogenesis of dolomite hydrocarbon reservoirs. Geological Society of London, Special Publication 235, 1\u0026ndash;6.\u003c/li\u003e\n \u003cli\u003eCruset, D., Verg\u0026eacute;s, J., Mu\u0026ntilde;oz-L\u0026oacute;pez, D., Moragas, M., Cantarero, I., Trav\u0026eacute;, A., 2023. Fluid evolution from extension to compression in the Pyrenean Fold Belt and BasqueCantabrian Basin: a review. Earth-Science Reviews 243, 104494.\u003c/li\u003e\n \u003cli\u003eChen W, Mu C, Wang Q et al. 2024. Study on U-Pb age and provenance of detrital zircons from sandstones of the Shaximiao Formation, northwestern Sichuan Basin. Sedimentary Geology and Tethyan Geology, 44(03):613-629.\u003c/li\u003e\n \u003cli\u003eDuan J, Zheng J, Shen A et al., 2021. Characteristics and genesis of dolomite reservoir of the Lower Permian Qixia Formation in central Sichuan Basin. Marine Origin Petroleum Geology, 26(04):345-356.\u003c/li\u003e\n \u003cli\u003eFeng M, Qiang Z, Shen P et al., 2016. Evidences for hydrothermal dolomite of Sinian Dengying Formation in Gaoshiti-Moxi area,Sichuan Basin. Acta Petrolei Sinica. 37(05): 587-598.\u003c/li\u003e\n \u003cli\u003eGe X, Mu C, Men X, et al., 2023. Discussion on U-Pb Dating and Tectonic Setting of K- bentonites from Late Ordovician-Early Silurian Period in the Sichuan Basin. Sedimentary Geology and Tethyan Geology, 1-17.\u003c/li\u003e\n \u003cli\u003eHan X, Bao Z, Xie S et al., 2016. Origin and Geochemical Characteristics of Dolomites in the Middle Permian Formation,SW Sichuan Basin,China. Earth Science. 41(01): 167-176.\u003c/li\u003e\n \u003cli\u003eHan Y, Zhang J, He Z et al., 2023. Characteristics and development models of high-quality dolomite reservoirs in Middle Permian Qixia Formation, central Sichuan Basin. Natural Gas Exploration and Development, 44(01):75-88.\u003c/li\u003e\n \u003cli\u003eHe D, Li D, Zhang, G et al., 2011. Formation and evolution of multi-cycle superposed Sichuan Basin, China. Chinese Journal of Geology (Scientia Geologica Sinica).46(3):589-606.\u003c/li\u003e\n \u003cli\u003eHou G, Zhou J, Gu M et al., 2017. Lithofacies Paleogeography and Exploration Realms of Middle Permian Qixia Formation and Maokou Formation, Sichuan Basin. Marine Origin Petroleum Geology. 22(01): 25-31.\u003c/li\u003e\n \u003cli\u003eHu A, Pan L, Hao Y et al., 2018. Origin, Characteristics and Distribution of Dolostone Reservoir in Qixia Formation and Maokou Formation, Sichuan Basin, China. Marine Origin Petroleum Geology. 23(02): 39-52.\u003c/li\u003e\n \u003cli\u003eGeng G, Chen Y, Chen K et al., 2024. Distribution and activity of strike-slip faults in Gaoshiti area of Sichuan Basin and their control and significance for the development of dolomite reservoirs in Permian Qixia Formation. Acta Petrolei Sinica, 45(12):1761-1782.\u003c/li\u003e\n \u003cli\u003eHu M, Wei G, Hu Z et al., 2010. Sequence-lithofacies palaeogeography of the Middle Permian Qixia Formation in Sichuan Basin. Journal of Palaeogeography(Chinese Edition). 12(05): 515-526.\u003c/li\u003e\n \u003cli\u003eJones, G.D., Whitaker, E.L., Smart, E.L., Sanford, W.E., 2004. Numerical analysis of seawater circulation in carbonate platforms: II. The dynamic interaction between geothermal and brine reflux circulation. American Journal of Science 304, 250\u0026ndash;284.\u003c/li\u003e\n \u003cli\u003eKeith M L, Weber J N. 1964. Carbon and oxygen isotopic composition of selected limestones and fossils. Geochimica Et Cosmochimica Acta. 28(10\u0026ndash;11): 1787-1816.\u003c/li\u003e\n \u003cli\u003eKawabe, I., Toriumi, T., Ohta, A., Miura, N., 1998. Monoisotopic REE abundances in seawater and the origin of seawater tetrad effect. Geochemical Journal 32, 213\u0026ndash;230.\u003c/li\u003e\n \u003cli\u003eKorte, C., Jasper, T., Kozur, H.W., Veizer, J., 2005. \u0026delta;18Oand\u0026delta;13C of Permian brachiopods: a record of seawater evolution and continental glaciation. Palaeogeography, Palaeoclimatology, Palaeoecology. 224 (4), 333\u0026ndash;351.\u003c/li\u003e\n \u003cli\u003eLiu S, Yang Y, Deng B et al., 2021a. Tectonic evolution of the Sichuan Basin, Southwest China. Earth Science Reviews 213.\u003c/li\u003e\n \u003cli\u003eLi R, Hu M, Yang W et al., 2019. Sedimentary facies model and favorable reservoir distribution of the Middle Permian in Sichuan Basin. Oil \u0026amp; Gas Geology, 40(02):369-379.\u003c/li\u003e\n \u003cli\u003eLiu W, Zhong D, Sun H et al., 2021. Sedimentary Characteristics and Paleogeomorphic Responses of the Middle Permian Qixia Formation in the Northwestern Sichuan Basin. Acta Sedimentologica Sinica, 39(05):1275-1291.\u003c/li\u003e\n \u003cli\u003eLi X，Huang S，Huang S et al., 2016a. Petrologic and geochemical characteristics and the origin of dolomites in the Qixia Formation in Nanjiang county of the Sichuan Basin. Petroleum Geology \u0026amp; Experiment, 38(02):251-258.\u003c/li\u003e\n \u003cli\u003eLi X, Huang S, Huang K et al., 2016b. Geochemical characteristics of Middle Permian Qixia Fm dolomitized marine fluids in the Sichuan Basin. Natural Gas Industry, 36(10):35-45.\u003c/li\u003e\n \u003cli\u003eLu X, Gui L, Wang Z et al., 2024. Activity time of strike-slip faults and their controlling effects on hydrocarbon accumulation in central Sichuan Basin: evidence from U-Pb dating and fluid inclusions of cements in fault zone. Acta Petrolei Sinica, 45(04):642-658.\u003c/li\u003e\n \u003cli\u003ePan, L., Shen, A., Zhao, J., Hu, A., Hao, Y., Liang, F., Feng, Y., Wang, X., Jiang, L., 2020. LA-ICPMS U\u0026ndash;Pb geochronology and clumped isotope constraints on the formation and evolution of an ancient dolomite reservoir: the Middle Permian of northwest Sichuan Basin (SW China). Sedimentary Geology 407, 105728.\u003c/li\u003e\n \u003cli\u003ePei S, Wang X, Li R et al., 2021. Burial dolomitization of marginal platform bank facies and its petroleum geological implications: The genesis of Middle Permian Qixia Formation dolostones in the northwestern Sichuan Basin. Natural Gas Industry, 41(04):22-29.\u003c/li\u003e\n \u003cli\u003ePurser, B.H., Brown, A., Aissaoui, D.M., 1994. Nature, origin and evolution of porosity in dolomites. Special Publication International Association Sedimentologyvol. 21, pp. 283\u0026ndash;308.\u003c/li\u003e\n \u003cli\u003eShu X, Zhang J, Li G, et al. 2012. Characteristics and Genesis of hydrothermal dolomites of Qixia and Maokou Formations in northern Sichuan Basin. Oil\u0026amp;Gas Geology, 33(3):442-448.\u003c/li\u003e\n \u003cli\u003eSwennen, R., Dewit, J., Fierens, E., Muchez, P., Shan, M., Nader, F., Hunt, D., 2012. Multiple dolomitization events along the Pozalagua Fault (Pozalagua Quarry, BasqueCantabrian Basin, Northern Spain). Sedimentology 59, 1345\u0026ndash;1374.\u003c/li\u003e\n \u003cli\u003eVeizer, J., Ala, D., Azmy, K., Bruckschen, P., Buhl, D., Bruhn, F., Carden, G.A., Diener, A., Ebneth, S., Godderis, Y.J., 1999. 87Sr/86Sr, \u0026delta;13Cand\u0026delta;18O evolution of Phanerozoic seawater. Chemical Geology 161 (1\u0026ndash;3), 59\u0026ndash;88.\u003c/li\u003e\n \u003cli\u003eWang B, Song J, Liu S et al., 2024. Types and genetic modes of dolomite in the Member 2 of Middle Permian Maokou Formation in western Sichuan Basin. Acta Petrolei Sinica, 45(12):1743-1760.\u003c/li\u003e\n \u003cli\u003eWang H, Chi Y, Zhao Z et al., 2013. Karst reservoirs developed in the Middle Permian Qixia Formation of Sichuan Basin and selection of exploration regions. Acta Petrolei Sinica. 34(05): 833-842.\u003c/li\u003e\n \u003cli\u003eXu Z. 2019. Genesis and source of gas in Middle Permian Maokou Formation of eastern Sichuan Basin. Special Oil\u0026amp;Gas Reservoirs, 26(2):16-22.\u003c/li\u003e\n \u003cli\u003eYang L, Gu M, Yang X et al., 2015. High-resolution Characterization of Borehole-scaled Reservoir Structure:A Case of Lower Permian Qixia Dolostone Reservoir in Well Kuang-2, Northwest of Sichuan Basin. Marine Origin Petroleum Geology, 20(04):65-72.\u003c/li\u003e\n \u003cli\u003eYang Z, Sun H, Zhong D et al., 2024. Effects of basin tectonic evolution on multi-phase dolomitization: Insights from the Middle Permian Qixia Formation of the NW Sichuan Basin, SW China. Sedimentary Geology 470(000): 18.\u003c/li\u003e\n \u003cli\u003eYuan C, Wan Y, Liu X, et al. 2019. Fine characterization of reservoir heterogeneity in the Wellblock X of Longwangmiao Formation. Special Oil\u0026amp;Gas Reservoirs, 26(2):121-126.\u003c/li\u003e\n \u003cli\u003eZhang B, Xie J, Yin H et al., 2018. Characteristics and exploration direction of the Middle Permian carbonate reservoirs in the Longmenshan mountain areas, western Sichuan Basin. Natural Gas Industry. 38(02): 33-42.\u003c/li\u003e\n \u003cli\u003eZhang B, Fang J, Yin H et al., 2019. A breakthrough in high-yield horizontal gas wells and great exploration and development potential in deep conventional gas reservoirs in the Sichuan Basin. Natural Gas Industry. 39(12): 1-9.\u003c/li\u003e\n \u003cli\u003eZhang T, Su Y, She G et al., 2015 A study on the genetic model of hydrothermal dolomitization in Taq Taq oilfield, Kurdistan region, Iraq\u0026mdash;taking oilfield A in the Cretaceous in Zagros Basin as an example. Oil \u0026amp; Gas Geology. 36(03): 393-401.\u003c/li\u003e\n \u003cli\u003eZheng H, Yuan L, Liu B et al., 2020. Origins of Dolomitization Fluids within Middle Permian Coarse Dolomite, SW Sichuan Basin. Acta Sedimentologica Sinica, 38(03): 1-11.\u003c/li\u003e\n \u003cli\u003eZhou J, Yao G, Yang G et al., 2016. Lithofacies palaeogeography and favorable gas exploration zones of Qixia and Maokou Fms in the Sichuan Basin. Natural Gas Industry. 36(04): 8-15.\u003c/li\u003e\n \u003cli\u003eZhou J, Hao Y, Deng H et al., 2019. Genesis and distribution of vuggy dolomite reserviors of the Lower Permian Qixia Formation and Maokou Formation,western-central Sichuan Basin. Marine Origin Petroleum Geology. 24(04): 67-78.\u003c/li\u003e\n \u003cli\u003eZhong, Y., He, B., Mundil, R., Xu, Y., 2014. CA-TIMS zircon U\u0026ndash;Pb dating of felsic ignimbrite from the Binchuan section: implications for the termination age of Emeishan large igneous province. Lithos 204, 14\u0026ndash;19.\u003c/li\u003e\n\u003c/ol\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":"carbonates-and-evaporites","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"caev","sideBox":"Learn more about [Carbonates and Evaporites](http://link.springer.com/journal/13146)","snPcode":"13146","submissionUrl":"https://submission.nature.com/new-submission/13146/3","title":"Carbonates and Evaporites","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Sichuan Basin, Qixia Formation, Grain shoal facies, Dolomitization, Dolomite reservoirs","lastPublishedDoi":"10.21203/rs.3.rs-7007312/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7007312/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe grain shoal facies dolomites of the Qixia Formation in the Sichuan Basin exhibit extensive distribution, diverse types, and significant variations in reservoir quality. Based on core observations, thin section identifications, and geochemical analysis data, this study systematically compares the characteristics of platform-margin shoal and intra-platform shoal dolomite reservoirs in the Qixia Formation. Results demonstrate that platform-margin shoal dolomites feature greater single-layer thickness (average\u0026thinsp;\u0026gt;\u0026thinsp;5 m), stronger and more complete dolomitization (dolomite content\u0026thinsp;\u0026gt;\u0026thinsp;85%), characterized by burial dolomitization, with developed dissolution vugs and intercrystalline pores (average porosity 2.9%). In contrast, intra-platform shoal dolomites show thinner single layers (average\u0026thinsp;\u0026lt;\u0026thinsp;3 m), relatively lower and incomplete dolomitization (dolomite content 30%-60%), dominated by penecontemporaneous dolomitization, with reservoir spaces mainly composed of residual intergranular pores (average porosity 1.9%), exhibiting inferior physical properties compared to platform-margin shoal facies. Dolomite reservoirs with prolonged and complete dolomitization processes demonstrate better physical properties. The platform-margin shoal facies have higher energy, superior initial physical properties, and stronger fluid mobility compared to intra-platform shoal facies, providing more favorable diagenetic-reservoir forming conditions for multi-stage dolomitization. This holds significant implications for predicting favorable exploration zones of grain shoal facies dolomite reservoirs.\u003c/p\u003e","manuscriptTitle":"Dolomite Reservoir Differences in Characteristics and Controlling Factors of Grainstone Shoal facies in Qixia Formation, Sichuan Basin","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-07-15 02:38:32","doi":"10.21203/rs.3.rs-7007312/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-08-09T21:54:14+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-08-01T08:34:26+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-07-25T02:17:36+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"306108788130369834003126655570952038357","date":"2025-07-21T08:00:33+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"269048512470913227366689605246964672928","date":"2025-07-21T03:54:34+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"239088297126874618347770481819386811065","date":"2025-07-21T03:44:35+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-07-13T12:36:10+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"10390344577575299917966738341854932541","date":"2025-07-09T22:28:11+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-07-09T22:13:10+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-07-09T22:05:06+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-07-01T04:07:51+00:00","index":"","fulltext":""},{"type":"submitted","content":"Carbonates and Evaporites","date":"2025-06-30T07:06:42+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"carbonates-and-evaporites","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"caev","sideBox":"Learn more about [Carbonates and Evaporites](http://link.springer.com/journal/13146)","snPcode":"13146","submissionUrl":"https://submission.nature.com/new-submission/13146/3","title":"Carbonates and Evaporites","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"eb2f1a40-8c66-43b7-8cf1-d36a138820b7","owner":[],"postedDate":"July 15th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-11-17T15:59:11+00:00","versionOfRecord":{"articleIdentity":"rs-7007312","link":"https://doi.org/10.1007/s13146-025-01192-z","journal":{"identity":"carbonates-and-evaporites","isVorOnly":false,"title":"Carbonates and Evaporites"},"publishedOn":"2025-11-15 15:56:59","publishedOnDateReadable":"November 15th, 2025"},"versionCreatedAt":"2025-07-15 02:38:32","video":"","vorDoi":"10.1007/s13146-025-01192-z","vorDoiUrl":"https://doi.org/10.1007/s13146-025-01192-z","workflowStages":[]},"version":"v1","identity":"rs-7007312","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7007312","identity":"rs-7007312","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}