The Effect of Salt Movement and Migration on Geological Structures, Abnormal Pore Pressure, and Associated Risks in the Dezful Carbonate Basin, Southwest Iran

The Effect of Salt Movement and Migration on Geological Structures, Abnormal Pore Pressure, and Associated Risks in the Dezful Carbonate Basin, Southwest Iran | 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 The Effect of Salt Movement and Migration on Geological Structures, Abnormal Pore Pressure, and Associated Risks in the Dezful Carbonate Basin, Southwest Iran Vahid Bolandi, Dariush Hasanvand, Arman Heravi, Mohammad Hassan Aliee, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8471148/v1 This work is licensed under a CC BY 4.0 License Status: Under Revision Version 1 posted 12 You are reading this latest preprint version Abstract Salt tectonics is a globally significant geological process that profoundly influences basin evolution, hydrocarbon trapping, and drilling safety in many sedimentary provinces, such as the Gulf of Mexico, North Sea, and Zagros Basin. However, understanding how salt movement interacts with compressional tectonics to modify structural geometry and pore pressure remains a critical challenge. This study focuses on the Dezful Embayment in the Zagros Basin, where salt mobility within the Gachsaran Formation exerts a dominant control on deformation style, pore pressure regimes, and drilling risks. Using integrated seismic interpretation, well log analysis, and structural modeling, an anticline in southwestern Iran was investigated to evaluate the interplay between salt migration and regional compression. Results reveal that the Gachsaran Formation functions as a major detachment horizon, generating structural disharmony between subsalt and suprasalt packages. Subsalt units (Asmari, Pabdeh, Gurpi, and Ilam formations) exhibit pronounced fold-axis rotation and misalignment relative to the overlying Gachsaran, Mishan, and Aghajari formations, which deform more smoothly due to stress buffering by the salt layer. Localized salt thickening at anticline crests correlates with abnormal pore pressure zones, and borehole instability. Drilling data confirm mud losses, saltwater influx, and wellbore collapse within these complex intervals. Overall, the findings demonstrate that halokinetic processes intensify operational risks by forming unpredictable pressure compartments and complex fracture networks. This study not only enhances understanding of salt–tectonic interactions in the Dezful Embayment but also provides practical insights for safer and more efficient drilling strategies in salt-prone basins worldwide. Dezful Embayment Gachsaran Formation Salt tectonics Abnormal pore pressure Drilling hazards Hydrocarbon exploration Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Introduction Salt tectonics, together with abnormal pore pressure are globally significant processes having an intense impact on hydrocarbon exploration, structural evolution, and drilling operation safety, respectively. As a consequence of their inherently ductile nature, salt deposits are capable of experiencing considerable degree of plastic deformation so they can flow while accompanied by pressure and act as décollement horizons; consequently, decoupling the deformation of competent and incompetent rock layers (Gemmer et al., 2004 ; Hudec & Jackson, 2007 ; Urai et al., 2008 ; Leš, 2022 ). This sort of mobility creates complex geological structures such as folds, thrusts, and rotated blocks, and also changes fluid migration pathways as well as pore pressure regimes (Tingay et al., 2011 ; Nikolinakou et al., 2018 ; Hauser, 2020 ; Hassanpour et al., 2021 ; Duffy et al., 2023 ). In many sedimentary basins worldwide including the Gulf of Mexico, the North Sea, and off-shore Brazil, these processes are closely linked with abnormal pressure conditions responsible for drilling hazards such as kicks, blowouts, and influx of salt water (Karakitsios et al., 2001 ; Biju-Duval, 2002 ; Schoenherr et al., 2007 ; Dooley et al., 2012 ; Weijermars et al., 2014 ; Luo et al., 2017 ; Strozyk, 2017 ; Venera and Mario, 2019 ; Baquero Rico, 2022 ; ANJOS et al., 2024 ). The knowledge about the processes through which the movement of salts and compressional forces from tectonics regulate pore pressure is henceforth critical towards safe drilling and effective management of hydrocarcarbon resource exploration, particularly in tectonically active and salt-rich regions such as the Zagros Basin. Within this global context, the Dezful Embayment in the Zagros Basin of southwest Iran provides an especially significant natural laboratory. It is a highly productive hydrocarbon province of the Middle East, whose complex tectonic history has provided the favorable environment for oil and gas accumulations (Koop & Stoneley, 1982 ; Motiei, 1993 ; Bordenave & Huc, 1995 ). The basin has evolved with an extensive tectonic history driven by collision between the Arabian and Eurasian plates, involving uplift, folding, and thrust faulting (Berberian, 1995 ; Alavi, 2004 ; Agard et al., 2011 ). One of the distinguishing features of the Dezful Embayment is the occurrence of thick salts, especially the evaporitic Gachsaran Formation (Motiei, 1993 ; Bordenave & Huc, 1995 ). The salts are plastic with increasing pressure (Munson, 1997 ; Fredrich et al., 2003 ), acting as a main décollement surface decoupling overlying from underlying units (Sepehr & Cosgrove, 2004 ; Sherkati et al., 2005 ; Callot et al., 2012 ). This process enables numerous folds above and below the Gachsaran Formation to be developed and significantly controls structural evolution and pressure regimes within the Zagros foreland fold-and-thrust belt (Sepehr et al., 2006 ; Ghanadian et al., 2017 ; Najafi et al., 2018 ). Despite the extensive amount of work invested in the tectonic history and hydrocarbon systems of the Zagros Basin (Berberian, 1995 ; Alavi, 2004 ; Sepehr et al., 2006 ; Kordi, 2019 ; AbdollahieFard et al., 2019 ; Sun et al., 2023 ; Alipour, 2024 ), the collaborative action of salt movement and compressional forces on the growth of abnormal pore pressure within the Dezful Embayment has not received enough academically attention. Previous works have largely emphasized structural deformation or hydrocarbon accumulation, and thus the role of salt movement in controlling pore pressure and its companion drillability risks has not been sufficiently studied. This study addresses this gap through analyzing of an anticline in southwestern Iran, in the Zagros Basin (Fig. 1 ), to evaluate how tectonic interactions and salt movement contribute to abnormal pressure generation. Through the combination of seismic observance and structural description, we aim to clarify the processes underlying subsalt and suprasalt decoupling, development of fractures, and pathways of fluid migration. These investigations, in addition to enhancing knowledge of the Dezful Embayment, also contribute to more general geologic models of salt-related deformation and pressure regimes in analogous petroleum basins worldwide. Geological background The Zagros Basin, located in southwestern Iran, is a notable geological feature known for its complicated tectonic evolution and numerous sedimentary environments, formed during the Cenozoic era through process of closing Neo-Tethys Ocean occurred by the northward convergence of the Arabian plate toward the Eurasian plate (Fig. 2 ). The basin which is characterized by a series of parallel northwest-southeast mountain ranges, reflecting the compressional deformation of the sedimentary cover on the Arabian continental margin (Berberian, 1995 ; Sarkarinejad & Goftari, 2019 ; Seraj et al., 2020 ), is comprised of both marine and continental sedimentary layers (Berberian, 1995 ; Allen & Armstrong, 2008 ; Kordi, 2019 ; Jafari et al., 2023 ; Alipour, 2024 ). In addition to its tectonic complexity, the Zagros fold and thrust belt is famous for its huge oil and gas storage, which are predominantly trapped within the folded and faulted sedimentary sequences (Koop & Stoneley, 1982 ). The basin's geological framework gives excellent insights into basin formation, sedimentation, and tectonic processes, making it an important region for academic research and resource exploitation (Bahroudi & Koyi, 2004 ; Sembroni et al., 2024 ). Dezful Embayment The Dezful embayment is a prominent geologic feature within the Zagros fold and thrust belt in southwest of Iran, characterized by a complex system of structural highs and lows (Berberian, 1995 ; Alavi, 2004 ). The complex structural architecture combined with the presence of favorable source rocks, reservoir, and cap rock has made the Dezful Embayment a prolific hydrocarbon-producing region that are critical for both local and global energy markets (Motiei, 1993 ; Bordenave & Huc, 1995 ; Alipour, 2024 ). This region is still the focus of intensive geological research, emphasizing its importance in comprehending the Zagros Basin's overall tectonic and sedimentary processes. Therefore, the study of the interplay of tectonics and sedimentation in the Dezful Embayment, including the prominent Gachsaran evaporite formation, provides valuable insights into the processes governing basin evolution and the formation of hydrocarbon reservoirs in the Zagros region, as well as its contribution to geological complexity (Bahroudi & Koyi, 2003 ; Sherkati et al. 2005 ). Gachsaran Formation: The Gachsaran Formation, a key stratigraphic unit within the Dezful Embayment of southwestern Iran, plays a pivotal role in understanding the interplay between compressional tectonics and salt-related processes that contribute to abnormal pressure regimes in the region. This Formation is a thick evaporite sequence that was deposited during the Miocene epoch (Motiei, 1993 ). This formation is composed of a complex interbedding of anhydrite, halite, and Marl, with occasional thin layers of limestone sediments (Fig. 3 ), reflecting a complex depositional environment influenced by tectonic uplift and subsidence (Bordenave & Huc, 1995 ). The Gachsaran Formation plays a crucial role in the structural evolution of the Dezful Embayment, as the evaporites have acted as a primary décollement surface, facilitating the emplacement of thrust sheets and the development of complex fold structures (Sherkati et al., 2005 ) and exhibits a remarkable lateral and vertical variability in its lithological composition and thickness (Bahroudi & Koyi, 2003 ). This formation is composed of a complex interbedding which is including 7 sections as following from youngest to oldest Member1: This Member, known as the Cap Rock (Watson, 1960 ), constitutes the thinnest part of the Gachsaran Formation. It plays a crucial role in drilling operations by acting as a barrier that separates the high-pressure Gachsaran Formation from the low-pressure Asmari Formation. The Ideal cap rock consists of five evaporitic cycles, which include anhydrite, marl, limestone, and some bituminous shale. Member 2: This Member includes the thick layer of salt (Main Salt) and an alternating sequence of anhydrite, gray marls, and thin limestone bands. In the upper parts of this Member, some sylvite has been reported in certain drilled wells. The salts in this Member are among the thickest salts of the Gachsaran Formation in the Dezful basin. Member 2 of the Gachsaran Formation consists of three thick salt layers and two anhydritic layers interspersed with thin marly layers. The thick and basal layer of this formation is known as the Main Salt. Member 3: The lithological composition of Member 3 of the Gachsaran Formation includes both thin and thick layers of anhydrite, gray marls, salt, and also thin interlayers of limestone. This Member presents significant challenges during drilling operations due to the presence of thick marl layers and limestone interlayers, which can lead to issues such as mud loss and tight holes. A notable feature of this Member is the presence of bituminous marls. In this Member, the anhydrites are thicker compared to Member four, and the number and thickness of the salt layers are also less than those in Member four. Member 4: This Member consists of a sequence of thick salts, gray marls, anhydrite, and a small amount of limestone layers. The anhydrite in this Member is thinner compared to Member 3. In certain areas, red marls are also observed within this sequence. The salts of this Member, like those in Member 2, exhibit maximum expansion. The majority of the tectonic phenomena including salt movements associated with the Gachsaran Formation are linked to salt masses within this Member. Given the thick salt layers in this Member, their migration and movement occur more quickly and easily. Key characteristics of this Member include saltwater flow and tight hole occurrence. Member 5: This Member includes a sequence of anhydrite, gray and red marls, salt, and thin limestone bands. Member Five begins according to Watson's description (1960) from the base of the last red marl and ends at the start of the first thick salt layer characteristic of Member Four. In this Member, gray marls are more prevalent than red marls. Member 6: This Member starts with red marl. In the lower parts of this Member, the main sequence primarily consists of anhydrite, red marls, and thin limestone bands. The middle Members contain salt layers, while the upper parts include anhydrite, as well as red and gray marls. The top of this Member marks the beginning of the high-pressure zone just below the first anhydrite layer. Member 7: This Member, if fully developed, consists of three evaporitic layers of anhydrite and two interlayers of gray marl containing a small amount of limestone, representing the final stage of evaporitic deposits and the transition to marine deposits. It marks the last extent of the low-pressure formations of Aghajari and Mishan, with its base resting on the high-pressure zone of Member 6 of the Gachsaran Formation. Notably, Member 7 has also exhibited high-pressure characteristics in certain areas, such as wells 42 and 62 in the Pazanan field (Motiei, 1993 ). This phenomenon can be attributed to the connection of high-pressure areas in the underlying Members through faulting. The limestone in this Member is cream-colored, highly porous, and contains numerous fossil fragments. Numerous studies have been conducted to unravel the stratigraphic complexities of the Gachsaran Formation in the Dezful embayment (Koop & Stoneley, 1982 ; Jahani et al., 2009 ; Farzipour-Saein et al., 2009 ). However, the complex tectonic behavior of the Gachsaran formation, particularly the movement and deformation of the salt layers, can pose significant challenges for drilling, well integrity, and overall reservoir management. Understanding the dynamics of salty formation creep within the Gachsaran formation is crucial for the successful and sustainable exploration and production of hydrocarbon resources in this oilfield and similar geological settings in the region. Materials and Methods This study employed an integrated approach combining seismic interpretation, well log analysis, and structural modeling to investigate the role of salt movement in structural evolution, abnormal pore pressure, and drilling risks across the study area. Seismic reflection profiles were analyzed to image subsurface architecture and identify salt-related features. Gamma Ray and image log data from drilled wells were used to establish stratigraphic correlations and stress orientations. Published stratigraphic charts (Motiei, 1993 ; Bordenave & Huc, 1995 ) and core descriptions further aided in delineating the Gachsaran Formation members and their lithological variability. Seismic interpretation focused on mapping key reflectors of the Asmari, Gachsaran, Mishan, and Aghajari formations. Special attention was given to salt-related geometries such as disharmonic folds, detachment surfaces, and rotated blocks, as well as structural decoupling between subsalt and suprasalt packages. Time slices and seismic attributes were also evaluated to detect faulting and fracture corridors linked to abnormal pore pressures. Structural cross-sections were constructed to assess deformation styles of the study anticline. Evidence for asymmetric folding was examined to determine whether upper and lower anticlines formed through salt detachment, along with analysis of salt thickening, migration pathways, and fold-axis rotation. Image log data provided complementary insight by providing borehole breakouts and drilling-induced fractures analyzing to determine maximum and minimum horizontal stress orientations (Shmax and Shmin). These stress directions were compared with the regional Zagros tectonic framework. Drill records indicating mud losses, kicks, and influx of saltwater were interpreted as an indicator of anomalous pore pressure and correlated with lithological boundaries across the Gachsaran Formation. Integration of seismic, structural, and well information with drilling reports enabled the identification of key operational risks. This included mud loss associated to pressure increases, borehole instability due to salt creep, and unforeseen interactions with overpressured brine. Observations from this analysis were integrated within a conceptual model of the study anticline, highlighting the influence of salt in controlling deformation, pressure distribution, and drilling-linked hazards. Result The integrated analysis of seismic data, well logs, and structural observations reveals several key findings regarding the influence of salt mobility on deformation patterns, pore pressure distribution, and drilling conditions in the Dezful Embayment. Structural Features from Seismic Interpretation Seismic reflection profiles show that the Gachsaran Formation functions as a major detachment horizon. Distinct salt-related geometries are identified, including disharmonic folding, rotated blocks, and detachment surfaces (Fig. 4 ). The anticline structure is expressed in two packages: The lower anticline, composed of the Asmari, Pabdeh, Gurpi, and Ilam formations, displays an oval geometry consistent with strong lateral compression. The upper anticline, consisting of the Gachsaran, Mishan, and Aghajari formations, exhibits a more circular geometry that becomes progressively smoother toward shallower levels. Image log and seismic evidences reinforce this interpretation. Borehole breakouts and drilling-induced fractures in the subsalt Asmari Formation indicate stress orientations, consistent with active tectonic forcing and structural realignment of Zagros (Fig. 5 ). Meanwhile, the upper formations display less rotation, confirming that the influence of compressional stress diminishes upward due to the intervening salt layer according to seismic time slices (Fig. 4 ). Seismic cross-sections and time slices (Fig. 6 ) demonstrate that the lower and upper anticlines are laterally and vertically misaligned, confirming structural disharmony between subsalt and suprasalt packages. Evidence of fold-axis rotation and localized salt thickening is concentrated within the lower structural levels. To further depict these variations, statistical information on thicknesses of different Gachsaran Formation members from this area of study is summarized in Table 1 . This supplementary dataset serves to highlight lateral as well as vertical variations in salt distribution and consequently validates seismic evidence of localized thickening. The geological examination of the area under investigation disclosed several significant characteristics. Owing to the prominent movement of salt and the tectonic activity present in the region, the upper part of the Gachsaran Formation as well as Mishan Formation, along with the Aghajari Formation, displayed minor fractures and faults. This structural deformation was particularly evident under the crest of the upper anticline package, where the salt movement was most pronounced. Furthermore, the analysis identified a sandstone layer that was sandwiched between overlying and underlying impermeable units (Gray Marl and Claystone). As a result of the displacement and faulting in this geological horizon, the sandstone had come into lateral contact with the impermeable marl layers. Consequently, any water or fluids that had accumulated within the sandstone became trapped and confined, unable to escape. The combination of the overburden pressure from the overlying formations and the upward movement of salt from below led to significant pressurization of these confined sandstone layers. This dynamic created displacement that allowed the sandstones to be positioned against the impermeable lithologies, potentially transforming them into high-pressure brine pockets. Table 1 Thickness variations of Gachsaran Mbr. Salt Thickness in the study area Well GS2 (m) GS3 (m) GS4 (m) GS5 (m) Well A 8.53 24.54 18.28 26.97 Well B 8.08 43.89 16.00 16.46 Well C 8.84 43.13 23.47 32.00 Well D 24.23 175.56 25.90 Not Drilled Thus, Operational records show that abnormal pore pressure occurrences, mud losses, and borehole instabilities are concentrated around anticline crests. These occurrences are strongest within the lower anticline package, where fault and fracture growth and abnormal pressures are most prominent. Salt-related features such as thickened zones are also coincidental with such high-risk zones. Discussion The integrated seismic, well log, and structural analyses provide new insights into the impact of salt mobility on structural evolution, pore pressure distribution, and drilling risks in the study area Embayment. Seismic interpretation (Fig. 4 ) highlights the role of the Gachsaran Formation as a major detachment horizon, producing structural disharmony between subsalt and suprasalt units. Distinct salt-related geometries, including disharmonic folding, rotated blocks, and detachment surfaces, are evident. These features indicate that halokinetic processes were a primary driver of structural complexity in the study area. The geometry of the anticlines further supports this interpretation. The lower anticline package, composed of the Asmari, Pabdeh, Gurpi, and Ilam formations, generally exhibits an oval-shaped geometry, reflecting strong lateral compression and rotation caused by forces transmitted from the Arabian plate. In contrast, the upper anticline package, comprising the Gachsaran, Mishan, and Aghajari formations, tends to display a more circular geometry from deeper to shallower depths. This contrast suggests that the Gachsaran salt layer acted as a mechanical buffer or décollement, absorbing tectonic stress and permitting subsalt units to deform more intensely while leaving the suprasalt package less affected. Image log (CBIL log) evidence reinforces this interpretation (Fig. 5 ). Induced fractures (Shmax orientation) and borehole breakouts indicate N57E/S57W and N47W/S47E, respectively (Figs. 5 & 7 ), which are aligned with the overall pattern of the Zagros Mountains stress directions, suggesting that the southwest regional structural framework shapes the directions of maximum and minimum stress directions (Fig. 8 ). Meanwhile, the upper formations display less rotation and more stable stress orientations, confirming that the influence of compressional stress diminishes upward due to the intervening salt layer. Seismic time slices and cross-sections (Fig. 4 ) further illustrate the decoupling effect. The lower anticlines are laterally and vertically misaligned with the upper anticlines, showing independent deformation histories. Evidence of salt thickening and fold-axis rotation is particularly pronounced in the lower package, while the upper anticlines display smoother geometries from deeper to shallower stratigraphic layers (Fig. 10 ). In more detail, in the Mishan Formation, the anticline closure is fairly symmetrical and elliptical, experiencing only slight rotation (~ 0–5°). The Gachsaran Formation reveals moderate rotation (~ 15–20°) such that the long axis is slightly oblique to the Mishan axis, indicating partial decoupling as the Gachsaran salt is functioning as a mobile horizon that accommodates differential slip. The salt layer also restrains the overlying Mishan and other supra-Gachsaran layers from compressional stress, accounting for their reduced degree of rotation than that of shallower units. Conversely, the suprasalt Formations reveals the most pronounced rotation of the anticline axis, wherein for the Asmari Formation the long axis is considerably oblique (~ 30–40° clockwise compared to Mishan) and closure elongated (Fig. 4 ), showing greater deformation under the influence of higher compressional stress. Salt mobility allows detachment folding, differential rotation, as well as stress partitioning across horizons, and the observed anticline disharmony presents strong support that the Gachsaran Formation is, in fact, actively deforming and migrating. From a drilling perspective, this means that subsurface closures may not align with surface structures, and stress regimes within subsalts are rotated, more complex, directly affecting the orientation of fractures, the regimes of pore pressure, as well as drilling hazards. The Gachsaran formation is composed of salt, anhydrite, limestone, and red and gray marls. Salt's inherent characteristics make it more malleable than other rock types, allowing it to distort and fold more easily when subjected to earth's stress. Because of this, a salt layer is more likely to fold when it is adjacent to layers of anhydrite, limestone, or marl because it has less resistance to deformation (Fig. 9 ). This interaction not only results in the development of steeper folds within the geological structure (Fig. 9 B) but also serves as a significant driving force for the movement of the salt layer itself. Basically, all salts deform under stress, which may be defined as a time-dependent plastic deformation of a material under stress. This plasticity, together with its lower specific gravity in comparison to surrounding rocks, contributing to the formation of structures like salt domes by permitting salt to flow and move over geological timescales, for instances those formed from the Hormuz series, which have gradually risen over time, causing the overlying rock layers to fold due to the pressure exerted by the moving salt. Some of these domes have even reached the surface, resulting in visible outcrops. Thus, the continuous, albeit very slow, movement of salts over geological time is supported by their inherent ability to migrate upward under tectonic forces. Therefore, due to its plastic properties, lower specific gravity, and high flexibility, salt tends to move upward over time. This upward movement is particularly intensified in the context of Zagros folding, where salt exploits governing geological conditions to increase its inclination and rise more steeply. Salt can move from high-pressure regions to lower-pressure regions within folded rock as a result of these intense geological pressures. In addition to facilitating salt migration, this dynamic process has the potential to cause extra folding and displacement of the surrounding rock layers, which would further alter the geological structures. Based on salt movement, we observe that in some anticlines, the geological formations down to the Gachsaran formation have developed in parallel layers. Bellow the Gachsaran formation, the Asmari formation and the lowewr layers, exhibit axes that shift relative to the upper anticline including the Gachsaran, Mishan, and Aghajari formations. This leads to the possibility of two asymmetric anticlines stacked on each other: the lower anticline comprises the Asmari, Pabdeh, Gurpi and Ilam formations, while the upper anticline includes the Gachsaran, Mishan, and Aghajari formations. The seismic sections (Fig. 9 C and Fig. 4 ) display clear evidence of differential deformation caused by the presence of a mobile salt layer. The ductile nature of salt permits the subsalt rock masses to shift independently from the overlying layers. This mobility causes differential displacement, where the deeper anticlines shift relative to the shallower ones. The seismic reflections in Fig. 4 indicate that the lower folds are misaligned with the upper anticlines in the study area. This suggests that subsalt structures have reoriented over time. The majority of these salt movements associated with the Gachsaran Formation are linked to salt masses within Gachsaran 4, which is proved to be mostly halite in composition (Bahadori et al., 2011 ; Bavi et al., 2008; Liaghat et al., 2021 ; Soleimani et al., 2015). Different types of salts, namely halite, anhydrite, and gypsum, exhibit varying tectonic behaviors owing to their distinct physical and chemical properties. Halite has a lower Young's modulus; therefore, it is very ductile, that is, it tends to flow under pressure, promoting halokinetic processes, such as salt movement. Halite density, approximately 2.16 g/cm 3 , is lower than most other sedimentary rocks. This causes buoyant upward flow of deeply buried salt. It can undergo significant deformation without fracturing, which affects the surrounding geological structures during tectonic movements. Due to this salt movement and tectonic pressure, we can observe small fractures and faults in the upper part of the Gachsaran formation and the Mishan formation, as well as within the Aghajari Formation, where the salt movement is most pronounced, under the crest of the upper anticline package. This can lead to secondary displacement movements. Moreover, there may be a sandstone layer that is sandwiched between marls above and below. Due to the displacement in this geological horizon, the sandstone may come into contact with the marl layers laterally. As a result, any water that gathers in the sandstones becomes trapped and cannot escape, becoming confined. Due to the pressure from the layers above, along with the upward movement of salt from beneath, these sandstones can undergo considerable pressurization. Therefore, this dynamic creates displacement that allow the sandstones to be positioned against the impermeable lithologies, potentially transforming them into high-pressure brine pockets (Fig. 6 ). The interaction between tectonic movements and salt dynamics within the anticline is the second agent for further movements in the study area. Because of its ductility the salt does not fracture in the subsurface during subsidence and geological deformation, instead it flows and folds at various scales (Arrhenius & Lachmann, 2003 ; Hudec et. Al., 2013 ; Alsop et al., 2015 ; Jackson & Hudec, 2017 ; Rodriguez et al., 2018 ). While the salt deposits are often considered as a homogenous mass, drilling and mining reveal that they are layered and composed of very different interbedded lithologies with contrasting viscosities and mechanical behavior (rheologies) like carbonates, anhydrites, and clays are brittle rocks with a high viscosity, whereas halite and K-Mg-rich salts are ductile rocks with a very low viscosity (Warren, 2006, 2010 ). The release of tectonic energy can generate low-pressure zones, while adjacent high-pressure areas facilitate the continuous upward movement of salt. This upward migration can lead to the formation of small fractures within the geological strata. When the anhydrite layers— acting as efficient seals for the high-pressure zones of Gachsaran Formation—are broken, the hydraulic pressure of saline water may be transferred from Gachsaran 4 or 6 to Gachsaran 7 and the upper layers, suggesting a plausible hydraulic connection. Notably, upon entering Gachsaran 7, we observed that the weight of the drilling mud was equivalent to that in Gachsaran 4, further indicating potential connectivity between these layers, like what has been seen in wells 42 and 62 in the Pazanan field, where Gachsaran 7 has also exhibited high-pressure characteristics which is attributed to the connection of high-pressure areas in the underlying sections through faulting (Motiei, 1993 ). Therefore, the redistribution of stress within the rock matrix caused by lower anticline rotation and shifting along with compaction, forces fluids into isolated zones through these small fractures, causing localized pressure increases. Moreover, the presence of small fractures may remain undetected due to the limitations inherent in seismic data collection, which typically only registers displacements greater than 20 meters. Consequently, displacements below this threshold often go unrecorded in seismic surveys. Within the intrest anticline, movements have been documented in Gachsaran 3, 4, and 5, while seismic data from other regions of Gachsaran reveal a lineament that corroborates the existence of a fault. However, if movements diminish gradually or if displacements in other layers are minor, such changes may not be reflected in seismic data, as they fall below the detectable range. These factors also represent a great risk for drilling operations for such wells, in which exposure to unconventional and unexpectedly high-pressure zones may create serious challenges. It is necessary to understand such dynamics to ensure appropriate drilling strategies and reduce possible hazards of subsurface pressures. These pressures are responsible for mostly operational hazards, including time delays caused in the process of drilling, and can contribute to the complete failure of a well. While this present research primarily deals with the long-term effects of salt displacement on structural evolution and pore pressure conditions, it should be mentioned that salt dynamics also generate diverse short-term effects outside the scope of this research. These involve quick surface deformation through uplift and subsidence, fault reactivation and mini-seismicity as a byproduct of stress redistribution, quick alteration of groundwater pathway and salinity, and sediment redistribution that can cause slope instability. All these mechanisms underscore the immediate geological hazards of salt tectonics but elevate the importance of preparedness via monitoring and control in salt-affecting fields. This investigation pinpoints the dominant role of tectonic compressional force and salt flow in the creation of abnormal pore pressures, but it is important to acknowledge additional potential contributing mechanisms that were not the primary focus of this analysis. Compaction disequilibrium, lateral pressure transfer, and diagenetic reactions (e.g., mineral dehydration) can also be factors in the creation of overpressure within sedimentary basins. In particular, rapid loading of sediments, coupled with low-permeability sealing lithologies, might may exacerbate pressurization independently of the movement of salts. These processes might be active simultaneously with halokinetic processes to augment localized areas of overpressure. Future studies combining basin modeling and geochemical analyses would be useful to quantify the relative influence of these adjunct mechanisms. Conclusion Our analysis indicates that tectonic pressure in the Zagros region, which causes folding, facilitates the movement of salt. This movement can result in two folded packages sliding over one another. A clear example of this phenomenon is observed in the study area’s anticline, where the Asmari, Pabdeh, and Gurpi have experienced slippage under formations, including the Aghajari, Mishan, and Gachsaran formations. This interaction has led to the formation of two asymmetric anticlines on top of each other— Asmari, Pabdeh, and Gurpi—moving along the axis of the anticline in relation to the Gachsaran, Mishan, and Aghajari formations. During drilling operations, it is crucial to consider the movement and thickening of salt towards the axis of the upper folded anticline. As highlighted in Fig. 6 , fractures may develop along the fold axis. These ruptures can result in encountering both low-pressure and high-pressure zones along the drilling path posing serious safety and operational challenges such as severe mud loss coincident of with gain and salt water flow, differential sticking in the low-pressure zones and mechanical stuck caused by well bore stability. If drilling progresses along the axis of the upper folded anticline, we are likely to encounter thickened salt layers, leading to increased pressure in that area. The displacement of salt can further likelihood of contribution to fractured network development in the layers. Therefore, from a drilling perspective, it is advisable to avoid drilling along this axis based on geophysical maps. For optimal target identification, it would be more beneficial to initiate drilling in areas with thinned salt layers that approach the flanks of the fold to reach the subsurface reservoirs. Upon reaching the Asmari formation, directional drilling should be employed to divert the drilling trajectory, thereby reducing exposure to risky zones, assuming the reservoir quality is critical. From an applied perspective, these findings highlight the importance of salt-related deformation and pressurization in drill trajectory planning. Avoiding the thickened salt zones along anticline crest by staying off the crest and targeting the flanks of folds with directional drilling can reduce exposure to high-risk intervals. Overall, the results of this research provide both new insights into the role of salt in structural evolution and practical guidance for mitigating drilling risks in salt-bearing basins across the world. Summary of Key Findings The results demonstrate that: The Gachsaran Formation acts as a major detachment horizon, producing structural disharmony between upper and lower anticlines. Subsalt units show stronger deformation, misalignment, and fold-axis rotation compared to suprasalt units. Stress rotation is observed primarily in the subsalt formations, while suprasalt formations remain comparatively stable. Drilling hazards, including abnormal pore pressure and borehole instability, are concentrated around anticline crests and correlate with zones of salt thickening and faulting. Declarations Author Contribution V.B. conceptualized the study “The Effect of Salt Movement and Migration on Geological Structures, Abnormal Pore Pressure, and Associated Risks in the Dezful Carbonate Basin, Southwest Iran,” conducted the main geological and geomechanical analyses, and wrote the original draft of the manuscript. D.H. contributed to the study design, interpretation of structural evolution and pore pressure data, and critically revised the manuscript. A.H. assisted with data processing, figure preparation, and methodological development. M.H.A. carried out the geophysical studies and provided the necessary datasets. O.T. supported data analysis, result validation, and manuscript editing. A.K. supervised the research, provided overall scientific guidance, and reviewed and finalized the manuscript. All authors read and approved the final version of the manuscript. Acknowledgement: I would like to express my sincere gratitude to Pezhvak Energy Engineering Company for their invaluable support. Special thanks go to Dr. Farid Mohamadi for his thorough and insightful review of this research. Your contributions have been truly instrumental to the success of this work. References Abdali, M.R., Mohamadian, N., Ghorbani, H. and Wood, D.A., 2021. Petroleum well blowouts as a threat to drilling operation and wellbore sustainability: causes, prevention, safety and emergency response. Journal of Construction Materials| Special Issue on Sustainable Petroleum Engineering ISSN, 2652, p.3752. 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14:39:15","extension":"png","order_by":10,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":51160,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-8471148/v1/765acdd6841ccff9b10d3b44.png"},{"id":99812933,"identity":"ecd40013-aa81-4816-be88-0b7cb42f50e2","added_by":"auto","created_at":"2026-01-08 14:38:11","extension":"png","order_by":11,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":2334236,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-8471148/v1/5932c5dccb24aa41f8071b34.png"},{"id":99813339,"identity":"f4414f37-2846-44df-9a99-147920807aa3","added_by":"auto","created_at":"2026-01-08 14:38:52","extension":"jpeg","order_by":12,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":628993,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage9.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8471148/v1/78b92b30fd566772b661e4d1.jpeg"},{"id":99813217,"identity":"f0bcd8a7-0f5a-4b75-beb6-5d27ec6fe779","added_by":"auto","created_at":"2026-01-08 14:38:39","extension":"png","order_by":13,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":115199,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-8471148/v1/90906ab6a1707915f74ea02d.png"},{"id":99813098,"identity":"824d56a3-8f7a-4d5a-8e2f-2197fef08e8c","added_by":"auto","created_at":"2026-01-08 14:38:25","extension":"png","order_by":14,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":102632,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage10.png","url":"https://assets-eu.researchsquare.com/files/rs-8471148/v1/c4bdcd0503a940f4a448ba64.png"},{"id":99813386,"identity":"56be3436-e966-4a1e-ac2d-cd661750ffe7","added_by":"auto","created_at":"2026-01-08 14:38:59","extension":"png","order_by":15,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":44060,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-8471148/v1/0b8411495b1cfe02ecf34714.png"},{"id":99813544,"identity":"41b9e325-cb96-46e3-861b-62de636d34e1","added_by":"auto","created_at":"2026-01-08 14:39:15","extension":"png","order_by":16,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":229474,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-8471148/v1/265ab7cbdef9d46de9ae1e76.png"},{"id":99813278,"identity":"1099c100-6438-4ab7-a33f-d983f6aa895f","added_by":"auto","created_at":"2026-01-08 14:38:47","extension":"png","order_by":17,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":284057,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-8471148/v1/59658d3a3a2548cd96e4bfb6.png"},{"id":99813317,"identity":"7dfe327b-f181-49cd-8f91-f31c9034dc24","added_by":"auto","created_at":"2026-01-08 14:38:49","extension":"png","order_by":18,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":588404,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-8471148/v1/967acf5c7745b88e56afd620.png"},{"id":99813503,"identity":"3a291455-0cec-465b-aed9-aab5b19d4a59","added_by":"auto","created_at":"2026-01-08 14:39:12","extension":"png","order_by":19,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":151847,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-8471148/v1/6f2b94f811d2ef40e0ebe230.png"},{"id":99813129,"identity":"1c9241a9-1683-42a7-ba9b-8e2e685035fc","added_by":"auto","created_at":"2026-01-08 14:38:26","extension":"png","order_by":20,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":11487,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-8471148/v1/5b123996278929c987446237.png"},{"id":99813384,"identity":"0b50161c-745b-4cd2-821f-b1d5f944b0bc","added_by":"auto","created_at":"2026-01-08 14:38:59","extension":"png","order_by":21,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":272596,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-8471148/v1/7d13c11f96f0a016d9885b5f.png"},{"id":99812961,"identity":"f77c410f-44b4-46a2-8510-3fc0deb1f45f","added_by":"auto","created_at":"2026-01-08 14:38:14","extension":"png","order_by":22,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":167799,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage9.png","url":"https://assets-eu.researchsquare.com/files/rs-8471148/v1/a00eb33ba8a592a93133adfb.png"},{"id":100356477,"identity":"2c479b9d-95fe-476d-ae39-5bc3878b9802","added_by":"auto","created_at":"2026-01-16 07:11:02","extension":"xml","order_by":23,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":133173,"visible":true,"origin":"","legend":"","description":"","filename":"39b04d00db524c3ca54169db8adf4af51structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-8471148/v1/0cc045195fd66d10c263cbcc.xml"},{"id":99813167,"identity":"46dcec2a-a09c-4b56-8a08-b7ecc938835c","added_by":"auto","created_at":"2026-01-08 14:38:34","extension":"html","order_by":24,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":142570,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8471148/v1/d91e2e43d779e7d0bcc87b9b.html"},{"id":100356622,"identity":"e5acabf6-8be6-4478-86ae-c421bc13fa17","added_by":"auto","created_at":"2026-01-16 07:16:09","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":942740,"visible":true,"origin":"","legend":"\u003cp\u003eTectonic framework of the Zagros fold-and-thrust belt and surrounding regions, showing the location of the Dezful Embayment in southwest Iran (adapted from Alavi, 2004). Major boundaries include the Main Frontal Fault (MFF) and Zagros Deformation Front (ZDF). The region circled off in the red box designated A is the particular region studied here, placed within the Dezful Embayment of the Zagros Fold Belt.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-8471148/v1/04f3d87fd992b9ef6416d702.png"},{"id":99813072,"identity":"f64b0d49-c460-4570-ab1d-72d36832fbc6","added_by":"auto","created_at":"2026-01-08 14:38:24","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":252113,"visible":true,"origin":"","legend":"\u003cp\u003eTectonic evolution of the Zagros Orogen in the realm of the Neotethys between the Central Iran and Arabian Plates (adapted from Ajirlu et al., 2016)\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-8471148/v1/dd1b393dda68b6e81dc3d02e.png"},{"id":99813215,"identity":"0085dcb9-3b17-4681-b9aa-530757ef891a","added_by":"auto","created_at":"2026-01-08 14:38:39","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1360813,"visible":true,"origin":"","legend":"\u003cp\u003e(Left) Geological map of Iran with the red box (A) indicating the location of the study area. (Right) Stratigraphic column of the Gachsaran Formation showing its full members and major lithologies, including anhydrite, marl, red marl, halite, and limestone, commonly found in the Zagros Basin.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-8471148/v1/0633b0f2111e3e8ebe01e65d.png"},{"id":99813292,"identity":"8446cc46-de44-4188-b16d-dd986e0e7646","added_by":"auto","created_at":"2026-01-08 14:38:48","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":2971085,"visible":true,"origin":"","legend":"\u003cp\u003eA: Time slice at the location of the Mishan Formation; B: Time slice at the location of the Gachsaran Formation; C: Time slice at the location of the Asmari Formation; D: Seismic Section of the study area in the North-South Direction\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-8471148/v1/6cbb899532886b293fdfad6a.png"},{"id":99813376,"identity":"dcf578c8-872e-4dc3-8b2f-b932657310e9","added_by":"auto","created_at":"2026-01-08 14:38:58","extension":"jpeg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":2716951,"visible":true,"origin":"","legend":"\u003cp\u003eThe CBIL image showing borehole breakouts and drilling induced fractures; Orientation of SHmax and SHmin in the Asmari Formation from drilling induced tensile fractures and borehole breakouts respectively.\u003c/p\u003e","description":"","filename":"floatimage5.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8471148/v1/a6888ab9e2c1f1b6d21de6bd.jpeg"},{"id":99813246,"identity":"17075255-a3bc-418c-ba45-77d8415889a7","added_by":"auto","created_at":"2026-01-08 14:38:44","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":1121490,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic three-dimensional perspective of the study area anticline and time slice from 3D seismic data of the Mishan Formation\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-8471148/v1/8a76c91a49367b8bd3dd5296.png"},{"id":99812869,"identity":"151d82a0-033b-46cf-adbd-1c840e81d91b","added_by":"auto","created_at":"2026-01-08 14:38:01","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":67401,"visible":true,"origin":"","legend":"\u003cp\u003eTypical borehole breakout and drilling induced fractures and Orientation of SHmax and SHmin (Fjaer et al., 1992).\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-8471148/v1/52e299da6a7c0ae89f80c5d0.png"},{"id":99812884,"identity":"bfe8cd61-2293-4ae0-9d7a-acbe4032e0db","added_by":"auto","created_at":"2026-01-08 14:38:02","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":2334236,"visible":true,"origin":"","legend":"\u003cp\u003eOrientation of maximum horizontal stress in Iran, derived from the World Stress Map database (Modified after M. Rajabi et al. 2010).\u003c/p\u003e","description":"","filename":"floatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-8471148/v1/41011400b0dde323eaca88d5.png"},{"id":99813264,"identity":"29bcc636-c7d5-4c8a-8eb9-7f470189ab3e","added_by":"auto","created_at":"2026-01-08 14:38:46","extension":"jpeg","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":628993,"visible":true,"origin":"","legend":"\u003cp\u003eA: A basic anticline structure, showing the typical folding of rock layers; B: Salt movement (halokinesis) and compressional tectonics play a crucial role in modifying the fold geometry resulted in Disharmonic folding where layers deform differently based on their mechanical properties; C: Schematic three-dimensional perspective of the study area anticline under unidirectional tectonic compression\u003c/p\u003e","description":"","filename":"floatimage9.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8471148/v1/df65cb246bf00f9e8dabf68a.jpeg"},{"id":99813151,"identity":"fc8cbe0c-34c9-41b2-9c9b-a65d698aac41","added_by":"auto","created_at":"2026-01-08 14:38:33","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":550916,"visible":true,"origin":"","legend":"\u003cp\u003eGachsaran Formation salt thickening correlation in SW- NE section\u003c/p\u003e","description":"","filename":"floatimage10.png","url":"https://assets-eu.researchsquare.com/files/rs-8471148/v1/63a0b2b7299ed1b16ce53d02.png"},{"id":100376721,"identity":"f510de3b-e463-4551-8301-c5f00d954e03","added_by":"auto","created_at":"2026-01-16 08:45:32","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":13103878,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8471148/v1/42da2b05-fc66-4efc-b3ad-81337049c338.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"The Effect of Salt Movement and Migration on Geological Structures, Abnormal Pore Pressure, and Associated Risks in the Dezful Carbonate Basin, Southwest Iran","fulltext":[{"header":"Introduction","content":"\u003cp\u003eSalt tectonics, together with abnormal pore pressure are globally significant processes having an intense impact on hydrocarbon exploration, structural evolution, and drilling operation safety, respectively. As a consequence of their inherently ductile nature, salt deposits are capable of experiencing considerable degree of plastic deformation so they can flow while accompanied by pressure and act as d\u0026eacute;collement horizons; consequently, decoupling the deformation of competent and incompetent rock layers (Gemmer et al., \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2004\u003c/span\u003e; Hudec \u0026amp; Jackson, \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Urai et al., \u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e2008\u003c/span\u003e; Leš, \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). This sort of mobility creates complex geological structures such as folds, thrusts, and rotated blocks, and also changes fluid migration pathways as well as pore pressure regimes (Tingay et al., \u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Nikolinakou et al., \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Hauser, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Hassanpour et al., \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Duffy et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). In many sedimentary basins worldwide including the Gulf of Mexico, the North Sea, and off-shore Brazil, these processes are closely linked with abnormal pressure conditions responsible for drilling hazards such as kicks, blowouts, and influx of salt water (Karakitsios et al., \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2001\u003c/span\u003e; Biju-Duval, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2002\u003c/span\u003e; Schoenherr et al., \u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Dooley et al., \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Weijermars et al., \u003cspan citationid=\"CR68\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Luo et al., \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Strozyk, \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Venera and Mario, \u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Baquero Rico, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; ANJOS et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). The knowledge about the processes through which the movement of salts and compressional forces from tectonics regulate pore pressure is henceforth critical towards safe drilling and effective management of hydrocarcarbon resource exploration, particularly in tectonically active and salt-rich regions such as the Zagros Basin.\u003c/p\u003e \u003cp\u003eWithin this global context, the Dezful Embayment in the Zagros Basin of southwest Iran provides an especially significant natural laboratory. It is a highly productive hydrocarbon province of the Middle East, whose complex tectonic history has provided the favorable environment for oil and gas accumulations (Koop \u0026amp; Stoneley, \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e1982\u003c/span\u003e; Motiei, \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e1993\u003c/span\u003e; Bordenave \u0026amp; Huc, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e1995\u003c/span\u003e). The basin has evolved with an extensive tectonic history driven by collision between the Arabian and Eurasian plates, involving uplift, folding, and thrust faulting (Berberian, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e1995\u003c/span\u003e; Alavi, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2004\u003c/span\u003e; Agard et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). One of the distinguishing features of the Dezful Embayment is the occurrence of thick salts, especially the evaporitic Gachsaran Formation (Motiei, \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e1993\u003c/span\u003e; Bordenave \u0026amp; Huc, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e1995\u003c/span\u003e). The salts are plastic with increasing pressure (Munson, \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e1997\u003c/span\u003e; Fredrich et al., \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2003\u003c/span\u003e), acting as a main d\u0026eacute;collement surface decoupling overlying from underlying units (Sepehr \u0026amp; Cosgrove, \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e2004\u003c/span\u003e; Sherkati et al., \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e2005\u003c/span\u003e; Callot et al., \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). This process enables numerous folds above and below the Gachsaran Formation to be developed and significantly controls structural evolution and pressure regimes within the Zagros foreland fold-and-thrust belt (Sepehr et al., \u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e2006\u003c/span\u003e; Ghanadian et al., \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Najafi et al., \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2018\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eDespite the extensive amount of work invested in the tectonic history and hydrocarbon systems of the Zagros Basin (Berberian, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e1995\u003c/span\u003e; Alavi, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2004\u003c/span\u003e; Sepehr et al., \u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e2006\u003c/span\u003e; Kordi, \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; AbdollahieFard et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Sun et al., \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Alipour, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2024\u003c/span\u003e), the collaborative action of salt movement and compressional forces on the growth of abnormal pore pressure within the Dezful Embayment has not received enough academically attention. Previous works have largely emphasized structural deformation or hydrocarbon accumulation, and thus the role of salt movement in controlling pore pressure and its companion drillability risks has not been sufficiently studied. This study addresses this gap through analyzing of an anticline in southwestern Iran, in the Zagros Basin (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e), to evaluate how tectonic interactions and salt movement contribute to abnormal pressure generation. Through the combination of seismic observance and structural description, we aim to clarify the processes underlying subsalt and suprasalt decoupling, development of fractures, and pathways of fluid migration. These investigations, in addition to enhancing knowledge of the Dezful Embayment, also contribute to more general geologic models of salt-related deformation and pressure regimes in analogous petroleum basins worldwide.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eGeological background\u003c/p\u003e \u003cp\u003eThe Zagros Basin, located in southwestern Iran, is a notable geological feature known for its complicated tectonic evolution and numerous sedimentary environments, formed during the Cenozoic era through process of closing Neo-Tethys Ocean occurred by the northward convergence of the Arabian plate toward the Eurasian plate (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The basin which is characterized by a series of parallel northwest-southeast mountain ranges, reflecting the compressional deformation of the sedimentary cover on the Arabian continental margin (Berberian, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e1995\u003c/span\u003e; Sarkarinejad \u0026amp; Goftari, \u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Seraj et al., \u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e2020\u003c/span\u003e), is comprised of both marine and continental sedimentary layers (Berberian, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e1995\u003c/span\u003e; Allen \u0026amp; Armstrong, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2008\u003c/span\u003e; Kordi, \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Jafari et al., \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Alipour, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). In addition to its tectonic complexity, the Zagros fold and thrust belt is famous for its huge oil and gas storage, which are predominantly trapped within the folded and faulted sedimentary sequences (Koop \u0026amp; Stoneley, \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e1982\u003c/span\u003e). The basin's geological framework gives excellent insights into basin formation, sedimentation, and tectonic processes, making it an important region for academic research and resource exploitation (Bahroudi \u0026amp; Koyi, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2004\u003c/span\u003e; Sembroni et al., \u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e2024\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eDezful Embayment\u003c/p\u003e \u003cp\u003eThe Dezful embayment is a prominent geologic feature within the Zagros fold and thrust belt in southwest of Iran, characterized by a complex system of structural highs and lows (Berberian, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e1995\u003c/span\u003e; Alavi, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2004\u003c/span\u003e). The complex structural architecture combined with the presence of favorable source rocks, reservoir, and cap rock has made the Dezful Embayment a prolific hydrocarbon-producing region that are critical for both local and global energy markets (Motiei, \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e1993\u003c/span\u003e; Bordenave \u0026amp; Huc, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e1995\u003c/span\u003e; Alipour, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). This region is still the focus of intensive geological research, emphasizing its importance in comprehending the Zagros Basin's overall tectonic and sedimentary processes. Therefore, the study of the interplay of tectonics and sedimentation in the Dezful Embayment, including the prominent Gachsaran evaporite formation, provides valuable insights into the processes governing basin evolution and the formation of hydrocarbon reservoirs in the Zagros region, as well as its contribution to geological complexity (Bahroudi \u0026amp; Koyi, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2003\u003c/span\u003e; Sherkati et al. \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e2005\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eGachsaran Formation:\u003c/p\u003e \u003cp\u003eThe Gachsaran Formation, a key stratigraphic unit within the Dezful Embayment of southwestern Iran, plays a pivotal role in understanding the interplay between compressional tectonics and salt-related processes that contribute to abnormal pressure regimes in the region. This Formation is a thick evaporite sequence that was deposited during the Miocene epoch (Motiei, \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e1993\u003c/span\u003e). This formation is composed of a complex interbedding of anhydrite, halite, and Marl, with occasional thin layers of limestone sediments (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e), reflecting a complex depositional environment influenced by tectonic uplift and subsidence (Bordenave \u0026amp; Huc, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e1995\u003c/span\u003e). The Gachsaran Formation plays a crucial role in the structural evolution of the Dezful Embayment, as the evaporites have acted as a primary d\u0026eacute;collement surface, facilitating the emplacement of thrust sheets and the development of complex fold structures (Sherkati et al., \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e2005\u003c/span\u003e) and exhibits a remarkable lateral and vertical variability in its lithological composition and thickness (Bahroudi \u0026amp; Koyi, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2003\u003c/span\u003e). This formation is composed of a complex interbedding which is including 7 sections as following from youngest to oldest\u003c/p\u003e \u003cp\u003eMember1: This Member, known as the Cap Rock (Watson, \u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e1960\u003c/span\u003e), constitutes the thinnest part of the Gachsaran Formation. It plays a crucial role in drilling operations by acting as a barrier that separates the high-pressure Gachsaran Formation from the low-pressure Asmari Formation. The Ideal cap rock consists of five evaporitic cycles, which include anhydrite, marl, limestone, and some bituminous shale.\u003c/p\u003e \u003cp\u003eMember 2: This Member includes the thick layer of salt (Main Salt) and an alternating sequence of anhydrite, gray marls, and thin limestone bands. In the upper parts of this Member, some sylvite has been reported in certain drilled wells. The salts in this Member are among the thickest salts of the Gachsaran Formation in the Dezful basin. Member 2 of the Gachsaran Formation consists of three thick salt layers and two anhydritic layers interspersed with thin marly layers. The thick and basal layer of this formation is known as the Main Salt.\u003c/p\u003e \u003cp\u003eMember 3: The lithological composition of Member 3 of the Gachsaran Formation includes both thin and thick layers of anhydrite, gray marls, salt, and also thin interlayers of limestone. This Member presents significant challenges during drilling operations due to the presence of thick marl layers and limestone interlayers, which can lead to issues such as mud loss and tight holes. A notable feature of this Member is the presence of bituminous marls. In this Member, the anhydrites are thicker compared to Member four, and the number and thickness of the salt layers are also less than those in Member four.\u003c/p\u003e \u003cp\u003eMember 4: This Member consists of a sequence of thick salts, gray marls, anhydrite, and a small amount of limestone layers. The anhydrite in this Member is thinner compared to Member 3. In certain areas, red marls are also observed within this sequence. The salts of this Member, like those in Member 2, exhibit maximum expansion. The majority of the tectonic phenomena including salt movements associated with the Gachsaran Formation are linked to salt masses within this Member. Given the thick salt layers in this Member, their migration and movement occur more quickly and easily. Key characteristics of this Member include saltwater flow and tight hole occurrence.\u003c/p\u003e \u003cp\u003eMember 5: This Member includes a sequence of anhydrite, gray and red marls, salt, and thin limestone bands. Member Five begins according to Watson's description (1960) from the base of the last red marl and ends at the start of the first thick salt layer characteristic of Member Four. In this Member, gray marls are more prevalent than red marls.\u003c/p\u003e \u003cp\u003eMember 6: This Member starts with red marl. In the lower parts of this Member, the main sequence primarily consists of anhydrite, red marls, and thin limestone bands. The middle Members contain salt layers, while the upper parts include anhydrite, as well as red and gray marls. The top of this Member marks the beginning of the high-pressure zone just below the first anhydrite layer.\u003c/p\u003e \u003cp\u003eMember 7: This Member, if fully developed, consists of three evaporitic layers of anhydrite and two interlayers of gray marl containing a small amount of limestone, representing the final stage of evaporitic deposits and the transition to marine deposits. It marks the last extent of the low-pressure formations of Aghajari and Mishan, with its base resting on the high-pressure zone of Member 6 of the Gachsaran Formation. Notably, Member 7 has also exhibited high-pressure characteristics in certain areas, such as wells 42 and 62 in the Pazanan field (Motiei, \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e1993\u003c/span\u003e). This phenomenon can be attributed to the connection of high-pressure areas in the underlying Members through faulting. The limestone in this Member is cream-colored, highly porous, and contains numerous fossil fragments.\u003c/p\u003e \u003cp\u003eNumerous studies have been conducted to unravel the stratigraphic complexities of the Gachsaran Formation in the Dezful embayment (Koop \u0026amp; Stoneley, \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e1982\u003c/span\u003e; Jahani et al., \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Farzipour-Saein et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). However, the complex tectonic behavior of the Gachsaran formation, particularly the movement and deformation of the salt layers, can pose significant challenges for drilling, well integrity, and overall reservoir management. Understanding the dynamics of salty formation creep within the Gachsaran formation is crucial for the successful and sustainable exploration and production of hydrocarbon resources in this oilfield and similar geological settings in the region.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cp\u003eThis study employed an integrated approach combining seismic interpretation, well log analysis, and structural modeling to investigate the role of salt movement in structural evolution, abnormal pore pressure, and drilling risks across the study area.\u003c/p\u003e \u003cp\u003eSeismic reflection profiles were analyzed to image subsurface architecture and identify salt-related features. Gamma Ray and image log data from drilled wells were used to establish stratigraphic correlations and stress orientations. Published stratigraphic charts (Motiei, \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e1993\u003c/span\u003e; Bordenave \u0026amp; Huc, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e1995\u003c/span\u003e) and core descriptions further aided in delineating the Gachsaran Formation members and their lithological variability. Seismic interpretation focused on mapping key reflectors of the Asmari, Gachsaran, Mishan, and Aghajari formations. Special attention was given to salt-related geometries such as disharmonic folds, detachment surfaces, and rotated blocks, as well as structural decoupling between subsalt and suprasalt packages. Time slices and seismic attributes were also evaluated to detect faulting and fracture corridors linked to abnormal pore pressures.\u003c/p\u003e \u003cp\u003eStructural cross-sections were constructed to assess deformation styles of the study anticline. Evidence for asymmetric folding was examined to determine whether upper and lower anticlines formed through salt detachment, along with analysis of salt thickening, migration pathways, and fold-axis rotation.\u003c/p\u003e \u003cp\u003eImage log data provided complementary insight by providing borehole breakouts and drilling-induced fractures analyzing to determine maximum and minimum horizontal stress orientations (Shmax and Shmin). These stress directions were compared with the regional Zagros tectonic framework. Drill records indicating mud losses, kicks, and influx of saltwater were interpreted as an indicator of anomalous pore pressure and correlated with lithological boundaries across the Gachsaran Formation.\u003c/p\u003e \u003cp\u003eIntegration of seismic, structural, and well information with drilling reports enabled the identification of key operational risks. This included mud loss associated to pressure increases, borehole instability due to salt creep, and unforeseen interactions with overpressured brine. Observations from this analysis were integrated within a conceptual model of the study anticline, highlighting the influence of salt in controlling deformation, pressure distribution, and drilling-linked hazards.\u003c/p\u003e "},{"header":"Result","content":"\u003cp\u003eThe integrated analysis of seismic data, well logs, and structural observations reveals several key findings regarding the influence of salt mobility on deformation patterns, pore pressure distribution, and drilling conditions in the Dezful Embayment.\u003c/p\u003e\u003ch2\u003eStructural Features from Seismic Interpretation\u003c/h2\u003e\u003cp\u003eSeismic reflection profiles show that the Gachsaran Formation functions as a major detachment horizon. Distinct salt-related geometries are identified, including disharmonic folding, rotated blocks, and detachment surfaces (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). The anticline structure is expressed in two packages:\u003c/p\u003e\u003cp\u003eThe lower anticline, composed of the Asmari, Pabdeh, Gurpi, and Ilam formations, displays an oval geometry consistent with strong lateral compression.\u003c/p\u003e\u003cp\u003eThe upper anticline, consisting of the Gachsaran, Mishan, and Aghajari formations, exhibits a more circular geometry that becomes progressively smoother toward shallower levels.\u003c/p\u003e\u003cp\u003eImage log and seismic evidences reinforce this interpretation. Borehole breakouts and drilling-induced fractures in the subsalt Asmari Formation indicate stress orientations, consistent with active tectonic forcing and structural realignment of Zagros (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). Meanwhile, the upper formations display less rotation, confirming that the influence of compressional stress diminishes upward due to the intervening salt layer according to seismic time slices (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e \u003c/p\u003e\u003cp\u003e \u003c/p\u003e\u003cp\u003eSeismic cross-sections and time slices (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e) demonstrate that the lower and upper anticlines are laterally and vertically misaligned, confirming structural disharmony between subsalt and suprasalt packages. Evidence of fold-axis rotation and localized salt thickening is concentrated within the lower structural levels. To further depict these variations, statistical information on thicknesses of different Gachsaran Formation members from this area of study is summarized in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. This supplementary dataset serves to highlight lateral as well as vertical variations in salt distribution and consequently validates seismic evidence of localized thickening. The geological examination of the area under investigation disclosed several significant characteristics. Owing to the prominent movement of salt and the tectonic activity present in the region, the upper part of the Gachsaran Formation as well as Mishan Formation, along with the Aghajari Formation, displayed minor fractures and faults. This structural deformation was particularly evident under the crest of the upper anticline package, where the salt movement was most pronounced. Furthermore, the analysis identified a sandstone layer that was sandwiched between overlying and underlying impermeable units (Gray Marl and Claystone). As a result of the displacement and faulting in this geological horizon, the sandstone had come into lateral contact with the impermeable marl layers. Consequently, any water or fluids that had accumulated within the sandstone became trapped and confined, unable to escape. The combination of the overburden pressure from the overlying formations and the upward movement of salt from below led to significant pressurization of these confined sandstone layers. This dynamic created displacement that allowed the sandstones to be positioned against the impermeable lithologies, potentially transforming them into high-pressure brine pockets.\u003c/p\u003e\u003cp\u003e \u003c/p\u003e\u003cdiv class=\"gridtable\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eThickness variations of Gachsaran Mbr. Salt Thickness in the study area\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003c/colgroup\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eWell\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGS2\u003c/p\u003e \u003cp\u003e(m)\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eGS3\u003c/p\u003e \u003cp\u003e(m)\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eGS4\u003c/p\u003e \u003cp\u003e(m)\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eGS5\u003c/p\u003e \u003cp\u003e(m)\u003c/p\u003e \u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eWell A\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e8.53\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e24.54\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e18.28\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e26.97\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eWell B\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e8.08\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e43.89\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e16.00\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e16.46\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eWell C\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e8.84\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e43.13\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e23.47\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e32.00\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eWell D\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e24.23\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e175.56\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e25.90\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eNot Drilled\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/table\u003e\u003c/div\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e \u003c/p\u003e\u003cp\u003eThus, Operational records show that abnormal pore pressure occurrences, mud losses, and borehole instabilities are concentrated around anticline crests. These occurrences are strongest within the lower anticline package, where fault and fracture growth and abnormal pressures are most prominent. Salt-related features such as thickened zones are also coincidental with such high-risk zones.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe integrated seismic, well log, and structural analyses provide new insights into the impact of salt mobility on structural evolution, pore pressure distribution, and drilling risks in the study area Embayment. Seismic interpretation (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e) highlights the role of the Gachsaran Formation as a major detachment horizon, producing structural disharmony between subsalt and suprasalt units. Distinct salt-related geometries, including disharmonic folding, rotated blocks, and detachment surfaces, are evident. These features indicate that halokinetic processes were a primary driver of structural complexity in the study area. The geometry of the anticlines further supports this interpretation. The lower anticline package, composed of the Asmari, Pabdeh, Gurpi, and Ilam formations, generally exhibits an oval-shaped geometry, reflecting strong lateral compression and rotation caused by forces transmitted from the Arabian plate. In contrast, the upper anticline package, comprising the Gachsaran, Mishan, and Aghajari formations, tends to display a more circular geometry from deeper to shallower depths. This contrast suggests that the Gachsaran salt layer acted as a mechanical buffer or d\u0026eacute;collement, absorbing tectonic stress and permitting subsalt units to deform more intensely while leaving the suprasalt package less affected. Image log (CBIL log) evidence reinforces this interpretation (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). Induced fractures (Shmax orientation) and borehole breakouts indicate N57E/S57W and N47W/S47E, respectively (Figs.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e \u0026amp; \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e), which are aligned with the overall pattern of the Zagros Mountains stress directions, suggesting that the southwest regional structural framework shapes the directions of maximum and minimum stress directions (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e). Meanwhile, the upper formations display less rotation and more stable stress orientations, confirming that the influence of compressional stress diminishes upward due to the intervening salt layer. Seismic time slices and cross-sections (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e) further illustrate the decoupling effect. The lower anticlines are laterally and vertically misaligned with the upper anticlines, showing independent deformation histories. Evidence of salt thickening and fold-axis rotation is particularly pronounced in the lower package, while the upper anticlines display smoother geometries from deeper to shallower stratigraphic layers (Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e). In more detail, in the Mishan Formation, the anticline closure is fairly symmetrical and elliptical, experiencing only slight rotation (~\u0026thinsp;0\u0026ndash;5\u0026deg;). The Gachsaran Formation reveals moderate rotation (~\u0026thinsp;15\u0026ndash;20\u0026deg;) such that the long axis is slightly oblique to the Mishan axis, indicating partial decoupling as the Gachsaran salt is functioning as a mobile horizon that accommodates differential slip. The salt layer also restrains the overlying Mishan and other supra-Gachsaran layers from compressional stress, accounting for their reduced degree of rotation than that of shallower units. Conversely, the suprasalt Formations reveals the most pronounced rotation of the anticline axis, wherein for the Asmari Formation the long axis is considerably oblique (~\u0026thinsp;30\u0026ndash;40\u0026deg; clockwise compared to Mishan) and closure elongated (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e), showing greater deformation under the influence of higher compressional stress. Salt mobility allows detachment folding, differential rotation, as well as stress partitioning across horizons, and the observed anticline disharmony presents strong support that the Gachsaran Formation is, in fact, actively deforming and migrating. From a drilling perspective, this means that subsurface closures may not align with surface structures, and stress regimes within subsalts are rotated, more complex, directly affecting the orientation of fractures, the regimes of pore pressure, as well as drilling hazards.\u003c/p\u003e \u003cp\u003eThe Gachsaran formation is composed of salt, anhydrite, limestone, and red and gray marls. Salt's inherent characteristics make it more malleable than other rock types, allowing it to distort and fold more easily when subjected to earth's stress. Because of this, a salt layer is more likely to fold when it is adjacent to layers of anhydrite, limestone, or marl because it has less resistance to deformation (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e). This interaction not only results in the development of steeper folds within the geological structure (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003eB) but also serves as a significant driving force for the movement of the salt layer itself. Basically, all salts deform under stress, which may be defined as a time-dependent plastic deformation of a material under stress. This plasticity, together with its lower specific gravity in comparison to surrounding rocks, contributing to the formation of structures like salt domes by permitting salt to flow and move over geological timescales, for instances those formed from the Hormuz series, which have gradually risen over time, causing the overlying rock layers to fold due to the pressure exerted by the moving salt. Some of these domes have even reached the surface, resulting in visible outcrops. Thus, the continuous, albeit very slow, movement of salts over geological time is supported by their inherent ability to migrate upward under tectonic forces. Therefore, due to its plastic properties, lower specific gravity, and high flexibility, salt tends to move upward over time. This upward movement is particularly intensified in the context of Zagros folding, where salt exploits governing geological conditions to increase its inclination and rise more steeply. Salt can move from high-pressure regions to lower-pressure regions within folded rock as a result of these intense geological pressures. In addition to facilitating salt migration, this dynamic process has the potential to cause extra folding and displacement of the surrounding rock layers, which would further alter the geological structures.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eBased on salt movement, we observe that in some anticlines, the geological formations down to the Gachsaran formation have developed in parallel layers. Bellow the Gachsaran formation, the Asmari formation and the lowewr layers, exhibit axes that shift relative to the upper anticline including the Gachsaran, Mishan, and Aghajari formations. This leads to the possibility of two asymmetric anticlines stacked on each other: the lower anticline comprises the Asmari, Pabdeh, Gurpi and Ilam formations, while the upper anticline includes the Gachsaran, Mishan, and Aghajari formations. The seismic sections (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003eC and Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e) display clear evidence of differential deformation caused by the presence of a mobile salt layer. The ductile nature of salt permits the subsalt rock masses to shift independently from the overlying layers. This mobility causes differential displacement, where the deeper anticlines shift relative to the shallower ones. The seismic reflections in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e indicate that the lower folds are misaligned with the upper anticlines in the study area. This suggests that subsalt structures have reoriented over time.\u003c/p\u003e \u003cp\u003eThe majority of these salt movements associated with the Gachsaran Formation are linked to salt masses within Gachsaran 4, which is proved to be mostly halite in composition (Bahadori et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Bavi et al., 2008; Liaghat et al., \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Soleimani et al., 2015). Different types of salts, namely halite, anhydrite, and gypsum, exhibit varying tectonic behaviors owing to their distinct physical and chemical properties. Halite has a lower Young's modulus; therefore, it is very ductile, that is, it tends to flow under pressure, promoting halokinetic processes, such as salt movement. Halite density, approximately 2.16 g/cm\u003csup\u003e3\u003c/sup\u003e, is lower than most other sedimentary rocks. This causes buoyant upward flow of deeply buried salt. It can undergo significant deformation without fracturing, which affects the surrounding geological structures during tectonic movements. Due to this salt movement and tectonic pressure, we can observe small fractures and faults in the upper part of the Gachsaran formation and the Mishan formation, as well as within the Aghajari Formation, where the salt movement is most pronounced, under the crest of the upper anticline package. This can lead to secondary displacement movements. Moreover, there may be a sandstone layer that is sandwiched between marls above and below. Due to the displacement in this geological horizon, the sandstone may come into contact with the marl layers laterally. As a result, any water that gathers in the sandstones becomes trapped and cannot escape, becoming confined. Due to the pressure from the layers above, along with the upward movement of salt from beneath, these sandstones can undergo considerable pressurization. Therefore, this dynamic creates displacement that allow the sandstones to be positioned against the impermeable lithologies, potentially transforming them into high-pressure brine pockets (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe interaction between tectonic movements and salt dynamics within the anticline is the second agent for further movements in the study area. Because of its ductility the salt does not fracture in the subsurface during subsidence and geological deformation, instead it flows and folds at various scales (Arrhenius \u0026amp; Lachmann, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2003\u003c/span\u003e; Hudec et. Al., \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Alsop et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Jackson \u0026amp; Hudec, \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Rodriguez et al., \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). While the salt deposits are often considered as a homogenous mass, drilling and mining reveal that they are layered and composed of very different interbedded lithologies with contrasting viscosities and mechanical behavior (rheologies) like carbonates, anhydrites, and clays are brittle rocks with a high viscosity, whereas halite and K-Mg-rich salts are ductile rocks with a very low viscosity (Warren, 2006, \u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). The release of tectonic energy can generate low-pressure zones, while adjacent high-pressure areas facilitate the continuous upward movement of salt. This upward migration can lead to the formation of small fractures within the geological strata. When the anhydrite layers\u0026mdash; acting as efficient seals for the high-pressure zones of Gachsaran Formation\u0026mdash;are broken, the hydraulic pressure of saline water may be transferred from Gachsaran 4 or 6 to Gachsaran 7 and the upper layers, suggesting a plausible hydraulic connection. Notably, upon entering Gachsaran 7, we observed that the weight of the drilling mud was equivalent to that in Gachsaran 4, further indicating potential connectivity between these layers, like what has been seen in wells 42 and 62 in the Pazanan field, where Gachsaran 7 has also exhibited high-pressure characteristics which is attributed to the connection of high-pressure areas in the underlying sections through faulting (Motiei, \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e1993\u003c/span\u003e). Therefore, the redistribution of stress within the rock matrix caused by lower anticline rotation and shifting along with compaction, forces fluids into isolated zones through these small fractures, causing localized pressure increases. Moreover, the presence of small fractures may remain undetected due to the limitations inherent in seismic data collection, which typically only registers displacements greater than 20 meters. Consequently, displacements below this threshold often go unrecorded in seismic surveys. Within the intrest anticline, movements have been documented in Gachsaran 3, 4, and 5, while seismic data from other regions of Gachsaran reveal a lineament that corroborates the existence of a fault. However, if movements diminish gradually or if displacements in other layers are minor, such changes may not be reflected in seismic data, as they fall below the detectable range. These factors also represent a great risk for drilling operations for such wells, in which exposure to unconventional and unexpectedly high-pressure zones may create serious challenges. It is necessary to understand such dynamics to ensure appropriate drilling strategies and reduce possible hazards of subsurface pressures. These pressures are responsible for mostly operational hazards, including time delays caused in the process of drilling, and can contribute to the complete failure of a well.\u003c/p\u003e \u003cp\u003eWhile this present research primarily deals with the long-term effects of salt displacement on structural evolution and pore pressure conditions, it should be mentioned that salt dynamics also generate diverse short-term effects outside the scope of this research. These involve quick surface deformation through uplift and subsidence, fault reactivation and mini-seismicity as a byproduct of stress redistribution, quick alteration of groundwater pathway and salinity, and sediment redistribution that can cause slope instability. All these mechanisms underscore the immediate geological hazards of salt tectonics but elevate the importance of preparedness via monitoring and control in salt-affecting fields.\u003c/p\u003e \u003cp\u003eThis investigation pinpoints the dominant role of tectonic compressional force and salt flow in the creation of abnormal pore pressures, but it is important to acknowledge additional potential contributing mechanisms that were not the primary focus of this analysis. Compaction disequilibrium, lateral pressure transfer, and diagenetic reactions (e.g., mineral dehydration) can also be factors in the creation of overpressure within sedimentary basins. In particular, rapid loading of sediments, coupled with low-permeability sealing lithologies, might may exacerbate pressurization independently of the movement of salts. These processes might be active simultaneously with halokinetic processes to augment localized areas of overpressure. Future studies combining basin modeling and geochemical analyses would be useful to quantify the relative influence of these adjunct mechanisms.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eOur analysis indicates that tectonic pressure in the Zagros region, which causes folding, facilitates the movement of salt. This movement can result in two folded packages sliding over one another. A clear example of this phenomenon is observed in the study area\u0026rsquo;s anticline, where the Asmari, Pabdeh, and Gurpi have experienced slippage under formations, including the Aghajari, Mishan, and Gachsaran formations. This interaction has led to the formation of two asymmetric anticlines on top of each other\u0026mdash; Asmari, Pabdeh, and Gurpi\u0026mdash;moving along the axis of the anticline in relation to the Gachsaran, Mishan, and Aghajari formations.\u003c/p\u003e \u003cp\u003eDuring drilling operations, it is crucial to consider the movement and thickening of salt towards the axis of the upper folded anticline. As highlighted in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e, fractures may develop along the fold axis. These ruptures can result in encountering both low-pressure and high-pressure zones along the drilling path posing serious safety and operational challenges such as severe mud loss coincident of with gain and salt water flow, differential sticking in the low-pressure zones and mechanical stuck caused by well bore stability.\u003c/p\u003e \u003cp\u003eIf drilling progresses along the axis of the upper folded anticline, we are likely to encounter thickened salt layers, leading to increased pressure in that area. The displacement of salt can further likelihood of contribution to fractured network development in the layers. Therefore, from a drilling perspective, it is advisable to avoid drilling along this axis based on geophysical maps.\u003c/p\u003e \u003cp\u003eFor optimal target identification, it would be more beneficial to initiate drilling in areas with thinned salt layers that approach the flanks of the fold to reach the subsurface reservoirs. Upon reaching the Asmari formation, directional drilling should be employed to divert the drilling trajectory, thereby reducing exposure to risky zones, assuming the reservoir quality is critical.\u003c/p\u003e \u003cp\u003eFrom an applied perspective, these findings highlight the importance of salt-related deformation and pressurization in drill trajectory planning. Avoiding the thickened salt zones along anticline crest by staying off the crest and targeting the flanks of folds with directional drilling can reduce exposure to high-risk intervals. Overall, the results of this research provide both new insights into the role of salt in structural evolution and practical guidance for mitigating drilling risks in salt-bearing basins across the world.\u003c/p\u003e"},{"header":"Summary of Key Findings","content":"\u003cp\u003eThe results demonstrate that:\u003c/p\u003e \u003cp\u003e \u003col\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe Gachsaran Formation acts as a major detachment horizon, producing structural disharmony between upper and lower anticlines.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eSubsalt units show stronger deformation, misalignment, and fold-axis rotation compared to suprasalt units.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eStress rotation is observed primarily in the subsalt formations, while suprasalt formations remain comparatively stable.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eDrilling hazards, including abnormal pore pressure and borehole instability, are concentrated around anticline crests and correlate with zones of salt thickening and faulting.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003c/ol\u003e \u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eV.B. conceptualized the study \u0026ldquo;The Effect of Salt Movement and Migration on Geological Structures, Abnormal Pore Pressure, and Associated Risks in the Dezful Carbonate Basin, Southwest Iran,\u0026rdquo; conducted the main geological and geomechanical analyses, and wrote the original draft of the manuscript. D.H. contributed to the study design, interpretation of structural evolution and pore pressure data, and critically revised the manuscript. A.H. assisted with data processing, figure preparation, and methodological development. M.H.A. carried out the geophysical studies and provided the necessary datasets. O.T. supported data analysis, result validation, and manuscript editing. A.K. supervised the research, provided overall scientific guidance, and reviewed and finalized the manuscript. All authors read and approved the final version of the manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgement:\u003c/h2\u003e \u003cp\u003eI would like to express my sincere gratitude to Pezhvak Energy Engineering Company for their invaluable support. Special thanks go to Dr. Farid Mohamadi for his thorough and insightful review of this research. Your contributions have been truly instrumental to the success of this work.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAbdali, M.R., Mohamadian, N., Ghorbani, H. and Wood, D.A., 2021. Petroleum well blowouts as a threat to drilling operation and wellbore sustainability: causes, prevention, safety and emergency response. Journal of Construction Materials| Special Issue on Sustainable Petroleum Engineering ISSN, 2652, p.3752.\u003c/li\u003e\n\u003cli\u003eAbdollahieFard, I., Sherkati, S., McClay, K. and Haq, B.U., 2019. Tectono-sedimentary evolution of the Iranian Zagros in a global context and its impact on petroleum habitats. In Developments in structural geology and tectonics (Vol. 3, pp. 17-28). Elsevier.\u003c/li\u003e\n\u003cli\u003eAgard, P., Omrani, J., Jolivet, L., Whitechurch, H., Vrielynck, B., Spakman, W., Moni\u0026eacute;, P., Meyer, B. and Wortel, R., 2011. Zagros orogeny: a subduction-dominated process. 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SPE.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"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":"Dezful Embayment, Gachsaran Formation, Salt tectonics, Abnormal pore pressure, Drilling hazards, Hydrocarbon exploration","lastPublishedDoi":"10.21203/rs.3.rs-8471148/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8471148/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eSalt tectonics is a globally significant geological process that profoundly influences basin evolution, hydrocarbon trapping, and drilling safety in many sedimentary provinces, such as the Gulf of Mexico, North Sea, and Zagros Basin. However, understanding how salt movement interacts with compressional tectonics to modify structural geometry and pore pressure remains a critical challenge. This study focuses on the Dezful Embayment in the Zagros Basin, where salt mobility within the Gachsaran Formation exerts a dominant control on deformation style, pore pressure regimes, and drilling risks. Using integrated seismic interpretation, well log analysis, and structural modeling, an anticline in southwestern Iran was investigated to evaluate the interplay between salt migration and regional compression. Results reveal that the Gachsaran Formation functions as a major detachment horizon, generating structural disharmony between subsalt and suprasalt packages. Subsalt units (Asmari, Pabdeh, Gurpi, and Ilam formations) exhibit pronounced fold-axis rotation and misalignment relative to the overlying Gachsaran, Mishan, and Aghajari formations, which deform more smoothly due to stress buffering by the salt layer. Localized salt thickening at anticline crests correlates with abnormal pore pressure zones, and borehole instability. Drilling data confirm mud losses, saltwater influx, and wellbore collapse within these complex intervals. Overall, the findings demonstrate that halokinetic processes intensify operational risks by forming unpredictable pressure compartments and complex fracture networks. This study not only enhances understanding of salt\u0026ndash;tectonic interactions in the Dezful Embayment but also provides practical insights for safer and more efficient drilling strategies in salt-prone basins worldwide.\u003c/p\u003e","manuscriptTitle":"The Effect of Salt Movement and Migration on Geological Structures, Abnormal Pore Pressure, and Associated Risks in the Dezful Carbonate Basin, Southwest Iran","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-08 14:01:43","doi":"10.21203/rs.3.rs-8471148/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-04-02T01:51:07+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-03-26T17:48:08+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-03-16T12:59:42+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"6843903688736693786207614493687774427","date":"2026-03-12T18:33:01+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"173595025352744489280549221478382668403","date":"2026-03-09T01:22:14+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-03-08T06:41:01+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"90550373504561532426984885091855976913","date":"2026-03-08T02:31:57+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"156727987559356993694986250407859561858","date":"2026-02-21T01:35:45+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-01-07T03:21:56+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-01-07T03:16:46+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-12-31T12:11:38+00:00","index":"","fulltext":""},{"type":"submitted","content":"Carbonates and Evaporites","date":"2025-12-29T08:46:57+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":"49dde4a8-39df-4acc-9074-df64eec150cd","owner":[],"postedDate":"January 8th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"in-revision","subjectAreas":[],"tags":[],"updatedAt":"2026-04-02T01:54:55+00:00","versionOfRecord":[],"versionCreatedAt":"2026-01-08 14:01:43","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8471148","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8471148","identity":"rs-8471148","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}