Marine and Petroleum Geology最新文献

{"title":"Diagenesis and burial history controls on Oligocene Huagang sandstones, southern Xihu Sag (East China Sea Basin): Implications for the formation of effective reservoirs","authors":"Hong-Liang Huo ,&nbsp;Cheng-Lin Liu ,&nbsp;Dao-Wu Huang ,&nbsp;An-Qi Tian ,&nbsp;Rizwan Sarwar Awan ,&nbsp;Hong-Yan Gao ,&nbsp;Chuang-Xin Liu ,&nbsp;Xue-Yong Chen ,&nbsp;Zi-Ye Tian ,&nbsp;Tao-Zheng Yang ,&nbsp;Bin-Bin Liu ,&nbsp;Chao-Jun Liang","doi":"10.1016/j.marpetgeo.2025.107592","DOIUrl":"10.1016/j.marpetgeo.2025.107592","url":null,"abstract":"<div><div>This study aims to reveal the diagenetic evolution sequence and controlling factors of Oligocene Huagang Formation (E₃h) sandstone reservoirs in the HY area, and predict high-quality reservoir distribution to guide hydrocarbon exploration. A comprehensive approach integrating core observation, thin-section petrography, geochemical analysis, and seismic-log interpretation was employed. By combining burial history simulation and diagenetic analysis, we systematically analyzed reservoir quality and diagenetic evolution and established evolution models for effective reservoir pore spaces. Results indicate that E₃h sandstones underwent intense diagenetic processes including compaction, cementation, and dissolution. Diagenesis plays a critical role in controlling reservoir quality: compaction is the primary factor that governs vertical variations in petrophysical properties, where shallower intervals typically exhibit better quality than deeper ones. In contrast, cementation and dissolution serve as secondary controls, explaining property differences between Blocks A and B, with Block A reservoirs being superior. A three-stage relationship has been identified between burial history and diagenesis: (1) early gradual subsidence stage (GSS) with weak feldspar dissolution, early carbonate cementation, chlorite coating, and mechanical compaction; (2) intermediate tectonic activity stage (TAS) with massive feldspar dissolution, quartz overgrowth precipitation, and ferruginous cement formation; (3) late stable burial stage (SBS) featuring intensified compaction and clay mineral transformations. The spatial configuration of fault systems and sandstones, combined with compositional attributes, strongly controls diagenetic evolution. Favorable zones for dissolution development occur at intersections of fault zones and acidic fluid migration pathways, while quartz-feldspar-rich zones mitigate porosity loss via compaction resistance. Three effective reservoir development models were proposed: high dissolution-low cementation-low compaction, moderate dissolution-low cementation-low compaction, and low compaction-low cementation-low dissolution. This research provides a critical basis for predicting E₃h high-quality reservoirs in the study area. Furthermore, the comprehensive burial history-diagenesis analysis method presented here offers a valuable reference for studies on sandstone diagenetic evolution and hydrocarbon exploration in similar geological settings.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"182 ","pages":"Article 107592"},"PeriodicalIF":3.6,"publicationDate":"2025-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145044394","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Depositional conditions affecting proximal to distal variation in the crystallo-chemical properties of Paleogene glauconites: Example from the Mesopotamian basin, Iraq","authors":"Tarang Sarin ,&nbsp;Santanu Banerjee ,&nbsp;Ibrahim Q. Mohammed ,&nbsp;Nibras Zaki ,&nbsp;Sherif Farouk ,&nbsp;Howri Mansurbeg ,&nbsp;Pragya Singh","doi":"10.1016/j.marpetgeo.2025.107591","DOIUrl":"10.1016/j.marpetgeo.2025.107591","url":null,"abstract":"<div><div>The proximal to distal variation in glauconite composition across a basin, although rarely attempted, may provide crucial insights into the depositional conditions. The Paleogene glauconites from the transgressive and condensed deposits are tracked from the proximal to the distal parts of the Mesopotamian basin in Iraq, to delineate their compositional variation. They prevail within the Paleocene Upper Aaliji Formation and the Eocene basal Jaddala Formation. The Fe₂O₃(total) (av. 16.78 wt%) and K₂O (av. 7.04 wt%) contents, and the ordering of the crystal structure and maturity (decreasing d-spacing and FWHM of 001 basal reflection) of glauconites increase, while the Al₂O₃ (av. 9.82 wt%) and MgO (av. 5.24 wt%) contents decrease from the proximal to distal settings. Therefore, the Al-rich and less mature glauconite is attributed to the proximal setting, whereas Fe-rich and more mature glauconites are attributed to the central and distal settings. The proximal setting is enriched with detrital Al-rich clay minerals forming less mature, Al-rich glauconites in kaolinite and illite-smectite precursors within the prevailing gently suboxic conditions. Whereas the central and distal settings sustain a lower sedimentation rate and enhanced mobility of ferrous ions, forming more mature, Fe-rich glauconites within the prevailing oxygen-depleted conditions. Glauconites form within two warming intervals from Late Danian to Late Ypresian and Late Lutetian to Late Bartonian. Warm climatic conditions amplify elemental supply, promote transgressive conditions, intensify reaction kinetics, and produce redox conditions encouraging abundant growth of glauconite. The composition and abundance of glauconites corroborate their formation within warm climatic conditions.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"182 ","pages":"Article 107591"},"PeriodicalIF":3.6,"publicationDate":"2025-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144921643","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Origin and controls on shale oil enrichment of bedding-parallel fractures in the Chang 73 lacustrine shales, Yanchang Formation, Ordos Basin","authors":"Zilong Li ,&nbsp;Kelai Xi ,&nbsp;Yingchang Cao ,&nbsp;Yifan Zhang ,&nbsp;Xiaobing Niu ,&nbsp;Xiujuan Wang ,&nbsp;Wenzhong Ma ,&nbsp;Yuan You ,&nbsp;Yuxuan Wang ,&nbsp;Guanghui Yuan","doi":"10.1016/j.marpetgeo.2025.107590","DOIUrl":"10.1016/j.marpetgeo.2025.107590","url":null,"abstract":"<div><div>As the main fracture type of lacustrine shales, bedding-parallel fractures (BPFs) play a key controlling role in diagenetic mass transfer as well as hydrocarbon migration and accumulation. To reveal the origin of BPFs and their controls on shale oil enrichment, this study integrates core, thin section, scanning electron microscopy (SEM) observations, and fluid inclusion analysis, focusing on the BPFs of the lacustrine shales of the Chang 7₃ sub-member, Yanchang Formation, Ordos Basin. The results show that the variations in mineral composition, arrangement, and size on both sides of the laminae interface induce significant mechanical anisotropy, which become the essential geological prerequisite for the generation and extension of BPFs along the laminae interface. Furthermore, influenced by the mineral planar fabrics, BPFs can also develop within the laminae. Compared with laminated shale, massive mudstone does not show significant BPFs development characteristics due to the lack of lamina fabric. As a consequence of disequilibrium compaction, the vertical seepage force gradient caused by hydrocarbon generation overpressure periodically breaks through the pressure threshold of the closed shale system, resulting in the episodic opening of weak interfaces, thereby constituting the major formation mechanism of BPFs. In addition, the tectonic compression effect near the basin margin can also promote the development of BPFs to a certain extent. In different lithofacies of shales, the differences in the development characteristics and degree of BPFs are mainly caused by the variations in laminae attributes including laminae combination, linear density, and average thickness. High total organic carbon (TOC) content is conducive to increasing hydrocarbon generation overpressure. However, excessive TOC content reduces the compressive strength of rocks and has an adverse effect on the development of BPFs. The analysis of shale oil production indicates that, compared with non-bedding-parallel fractures (NBPFs), BPFs play a dominant role in the enrichment of shale oil and can significantly increase the daily oil production of individual wells. These findings provide a theoretical basis for revealing the origin, development pattern of BPFs and their influence on fluid activity in lacustrine shales.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"182 ","pages":"Article 107590"},"PeriodicalIF":3.6,"publicationDate":"2025-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145010435","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"New data on the identification of magnesium-rich carbonate phases using Fourier Transform Infrared Spectroscopy","authors":"Katarzyna Stanienda-Pilecki ,&nbsp;Dariusz Łukowiec","doi":"10.1016/j.marpetgeo.2025.107585","DOIUrl":"10.1016/j.marpetgeo.2025.107585","url":null,"abstract":"<div><div>This paper presents the theory behind the importance and applicability of Fourier infrared spectroscopy in identifying carbonate phases with varying magnesium content. It presents the results of studies of Triassic limestone and dolomite samples taken from the Polish part of the Germanic Basin, which were analysed using this method. The scientific significance of the FTIR method lies in its ability to identify carbonate phases with varying magnesium content, even at low levels. FTIR is one of the few methods that offer such possibilities.</div><div>The following phases were analysed: low-Mg calcite, high-Mg calcite, dolomite and huntite. These carbonate phases were identified based on wave numbers occurring in the infrared absorption spectra. Low-Mg calcite is the dominant phase in the limestones. Some samples also contain a small amount of high-Mg calcite. Dolomite and huntite were also identified. High-Mg calcite and dolomite are prevalent in dolomites and dolomitic limestones. The research results indicate that the rocks of the Gogolin Unit (Lower Muschelkalk) and Diplopor Unit (Middle Muschelkalk) exhibit the least differentiation in carbonate phase content with varying magnesium contents, whereas the rocks of the Tarnowice and Boruszowice Units (Upper Muschelkalk) exhibit the most. The results suggest that the rocks of the Lower Muschelkalk (Gogolin Unit) and Middle Muschelkalk (Diplopor Unit) are quartz- and kaolinite-rich limestones. In contrast, the rocks of the Upper Muschelkalk (Tarnowice and Boruszowice units) are dolomites and dolomitic limestones. The results of the study demonstrate that Fourier infrared spectroscopy is one of the most effective methods for identifying carbonate phases with varying magnesium content, including those with magnesium substitution, due to its ease of use and high level of accuracy.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"182 ","pages":"Article 107585"},"PeriodicalIF":3.6,"publicationDate":"2025-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144893284","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"3D reconstruction of pore throat connectivity in Shale: An SAXS-MICP integrated framework","authors":"Linhao Zhang ,&nbsp;Shu Jiang ,&nbsp;Jiale Fu ,&nbsp;Fei Xie ,&nbsp;Zhile Han ,&nbsp;Zihao Li ,&nbsp;Mengdi Sun","doi":"10.1016/j.marpetgeo.2025.107584","DOIUrl":"10.1016/j.marpetgeo.2025.107584","url":null,"abstract":"<div><div>Digital rock technology enables simulation of reservoir dynamic response under coupled multi-physical fields, providing scientific basis for optimization of development schemes through virtual experiments. However, traditional CT technology shows significant limitations in processing low-porosity samples (&lt;5 %), with insufficient ability to accurately identify nano-scale throats, resulting in unrealistic isolated pore networks in reconstruction. Meanwhile, challenges remain in balancing resolution and field of view, as well as experimental cost and efficiency. To address these issues, this study innovatively introduces Small-Angle X-ray Scattering technology, leveraging its advantages of wide testing range, excellent sample representativeness, and ability to characterize closed pores. The research employs fast Gaussian random field method for 3D reconstruction, combines Delaunay triangulation and minimum spanning tree algorithms for network structure optimization, and integrates throat parameters obtained from mercury intrusion capillary pressure data. Finally, a low-porosity porous media model with realistic connectivity characteristics was successfully constructed, laying a solid foundation for detailed reservoir characterization and fluid transport mechanism research.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"182 ","pages":"Article 107584"},"PeriodicalIF":3.6,"publicationDate":"2025-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144892257","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Reservoir space types, controlling factors, and evolution models of interbedded shale in the Jurassic Lianggaoshan Formation, Sichuan Basin","authors":"Yan Wu ,&nbsp;Min Wang ,&nbsp;Xuefeng Bai ,&nbsp;Xin Wang ,&nbsp;Yu Sun ,&nbsp;Youzhi Wang ,&nbsp;Xinyi Yang ,&nbsp;Liang Xu ,&nbsp;Tianyi Li","doi":"10.1016/j.marpetgeo.2025.107583","DOIUrl":"10.1016/j.marpetgeo.2025.107583","url":null,"abstract":"<div><div>The type, structure, and origin of shale pores, which serve as both storage spaces for hydrocarbon accumulation and percolation pathways, fundamentally determine reservoir quality and further influence sweet spot identification and production performance in shale oil reservoirs. The heterogeneous interlayers such as siltstone and silty mudstone developed in continental shale have greatly altered the pore structure, fluid storage state and percolation capacity of the reservoir, resulting in significant differences in its reservoir properties compared with shale. This study investigates lacustrine interbedded shale reservoirs through a comprehensive approach incorporating X-ray diffraction (XRD), thin-section petrography, field emission scanning electron microscopy (FE-SEM), low temperature nitrogen adsorption, and nuclear magnetic resonance (NMR) techniques. The results demonstrate that the reservoir properties of different shale lithofacies are generally better than those of fine siltstone lithofacies, especially the organic-rich laminated argillaceous shale (O-rLAS) lithofacies, which has the best reservoir properties. Organic matter (OM) - related pores (particularly organo-clay composite pores) and the interlayer fractures/intercrystalline pores of clay mineral constitute the primary contributors to the reservoir space. Thermal cracking of organic matter and clay mineral transformation enhance the storage capacity of shale lithofacies, whereas cementation is identified as the main factor responsible for the poor reservoir quality of fine siltstone lithofacies. The development of OM-related pores is jointly controlled by thermal maturity, total organic carbon (TOC), and OM type, as well as clay mineral content. The occurrence state of clay minerals with OM and clay mineral type predominantly influence the development of clay mineral interlayer pores. Dissolution pores are mainly affected by TOC and felsic mineral content, while felsic mineral content significantly impacts the development of intergranular pores and microfractures. This study enriches the theoretical understanding of diagenetic and reservoir-forming mechanisms in continental shale reservoirs. It provides critical geological basis and theoretical support for accurately identifying and evaluating the high-quality \"sweet spots\" of continental interbedded shale oil. These findings offer practical guidance for efficient exploration and development of such complex reservoirs.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"182 ","pages":"Article 107583"},"PeriodicalIF":3.6,"publicationDate":"2025-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144863176","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cenozoic sedimentary records from the eastern offshore of China reveal the Eocene birth of the Yangtze River","authors":"Qian Zhao ,&nbsp;Hongtao Zhu ,&nbsp;Tandis S. Bidgoli ,&nbsp;Yiming Jiang ,&nbsp;Yinshan Chang ,&nbsp;Qianghu Liu ,&nbsp;Wei Wang","doi":"10.1016/j.marpetgeo.2025.107558","DOIUrl":"10.1016/j.marpetgeo.2025.107558","url":null,"abstract":"<div><div>The Yangtze River, which links the Tibetan Plateau to the eastern offshore of China, is one of the most important sediment routing systems in East Asia. However, the timing of its establishment has remained controversial. This study examines new and published zircon U-Pb geochronology data from eastern offshore basins (the East China Sea Shelf Basin and South Yellow Sea Basin) and major rivers in East Asia, establishing new constraints on the timing of full integration of the Yangtze River. We report detrital zircon U-Pb ages (n = 664) from Paleogene strata in the East China Sea Shelf Basin, the primary sink for the river during the Cenozoic. Detrital zircons from the Eocene to early Oligocene Pinghu Formation range from 34.9 ± 0.7 to 2800 ± 42 Ma, with 100–250 Ma and 1700–2100 Ma age clusters, and small Paleozoic, Neoproterozoic, and Paleoproterozoic-Archean peaks. A similar age range (33 ± 0.4 to 2842 ± 43 Ma) and nearly identical peaks are documented for the Oligocene Huagang Formation. The maximum depositional age, based on the youngest single grains in our samples, is 34.9 ± 0.7 Ma for Pinghu Formation and 33 ± 0.4 Ma for Huagang Formation. Statistical comparison of the new U-Pb ages with published data from sands collected in major segments of the modern Yangtze River and its estuary demonstrate similar provenance, but with larger contributions of 700–1000 Ma and 1700–2100 Ma zircons, sourced from the Songpan-Garze terrane. Additionally, the new data suggest that both the East China Sea Shelf Basin and the South Yellow Sea Basin retain young (&lt;80 Ma) zircons, likely sourced from the Jinshajiang segment of the Yangtze River. The youngest of these zircons are ∼37-33 Ma and only occur in sands from the upper reaches of the modern river. The high degree of similarity between the eastern offshore samples and the modern Yangtze system suggests the river and source-to-sink system were established by the late Eocene, and may point to topographic adjustments in the Qiangtang portion of the Tibetan Plateau as a driver of drainage expansion and integration.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"182 ","pages":"Article 107558"},"PeriodicalIF":3.6,"publicationDate":"2025-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144828920","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Facies architecture and depositional evolution of an Eocene tropical, shallow-marine, larger-benthic-foraminifera-dominated carbonate ramp, India","authors":"Sreetama Aich,&nbsp;Sudipta Dasgupta,&nbsp;Santanu Banerjee,&nbsp;Kumar Hemant Singh","doi":"10.1016/j.marpetgeo.2025.107582","DOIUrl":"10.1016/j.marpetgeo.2025.107582","url":null,"abstract":"<div><div>In contrast to the most cited carbonate ramp models, the middle Eocene Bombay Offshore Basin developed a unique facies association characterised by its depositional architecture. Based on the textural fabric and the significant biotic assemblages, seven sedimentary lithofacies and sixteen microfacies were classified and grouped into five facies associations that include: i) mid-ramp (FA I), ii) inner-ramp back-shoal (FA II), iii) inner-ramp fore-shoal (FA III), iv) inner-ramp shoal (FA IV), and v) inner-ramp sheltered-lagoon (FA V). Inter-well correlation depicts a heterogeneous mosaic distribution pattern of the depositional subenvironments, which, along with their respective depositional significances, leads us to develop an atypical depositional model for this shallow carbonate ramp deposit. The vertical sedimentary trends propose that several lower-order regressions overprint the basin-scale nth-order middle Eocene transgression. The succession is thus further subdivided into five (n+1)^th-order sequences (SQ I-V) and categorises the sedimentary evolution of the Bassein Formation into two phases. An initial mid-ramp setting (phase I) of the Lower Bassein Member is represented by the retrogradational or deepening-upward sequences of the platform development, followed by the deposition of the Middle and Upper Bassein members, defined by the consistent shallowing upward cycles during the late middle Eocene within the inner ramp, separated by a maximum flooding surface. Phase II of the studied formation shows complex depositional heterogeneity, where the low-energy backshoal and sheltered lagoon subenvironments contain heterogeneous intermittent intercalations of the higher energy bioclastic shoal bars and fore-shoal deposits. This heterogeneous mosaic microfacies distribution within a shallow-marine carbonate ramp deposit is attributed to the autogenic controls overprinting the allogenic controls. Further, the unique larger benthic foraminiferal assemblage of the formation provides a reasonable comparison with other contemporaneous carbonate platforms in the Circum-Tethyan belt, such as those in Oman and Iran, and offers a global analogue variant for the Eocene platform carbonates.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"182 ","pages":"Article 107582"},"PeriodicalIF":3.6,"publicationDate":"2025-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144852018","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Integrated seismic stratigraphic, sedimentological and petrophysical approaches for characterizing the Cenomanian reservoirs in transitional highs of north Western Desert intra-cratonic rift basins, Egypt","authors":"Ahmed Awadalla ,&nbsp;Ali Farag ,&nbsp;Andrea Moscariello ,&nbsp;Mahmoud Leila","doi":"10.1016/j.marpetgeo.2025.107581","DOIUrl":"10.1016/j.marpetgeo.2025.107581","url":null,"abstract":"<div><div>The Cenomanian Bahariya Formation is the most prolific hydrocarbon reservoir within the Mesozoic intra-cratonic rift basins of the Egyptian Western Desert. However, it remains under-explored in the transitional structural highs bordering these basins. These transitional regions host thin hydrocarbon pay zones in the sandstones of the Bahariya Formation. These sandstones exhibit pronounced petrophysical heterogeneity, which poses significant challenges to reservoir characterization and prediction, and their depositional characteristics and controls on the reservoir facies distribution have never been investigated. This study employs an integrated approach utilizing seismic stratigraphy, sedimentary facies analysis and petrophysics to establish the relationship between the Bahariya depositional patterns, reservoir rock types, and hydraulic flow units. Understanding these relationships is essential for assessing reservoir performance and identifying high-quality reservoir intervals for future exploration and production in these transitional regions. The studied core intervals comprise the Upper Bahriya reservoirs in two wells (Wadi El-Rayan-3X “WR-3X″ and Rayan-3X “R-3X”). The cored intervals consist mainly of sixteen sandstone, mudstone and siltstone lithofacies that were grouped into nine facies associations (FA) deposited in a muddy tide-dominated estuarine environment. Sandstone lithofacies were preferentially accumulated in narrow (&lt;1 km width) tidal channels (FA2) and sub-tidal bars (FA3). The sandstones of FA2, FA3 were classified as reservoir rock types (RRTs) 1 and 2 (RRT1, RRT2) with best reservoir characteristics and contribute to more than 90 % of the flow capacity of the Upper Bahariya reservoir. Conversely, mixed tidal flats (FA1) and intertidal sand bars (FA4) exhibit the poorest reservoir quality with pore system dominated by micropores and mesopores and act as effective fluid flow barriers. Petrophysical heterogeneity analysis indicates that sandstone lithofacies deposited within the outer estuarine tidal channels and subtidal bar environments exhibit the lowest degree of pore system heterogeneity. These facies are characterized by the dominance of well-connected macropores. The present results underscore the inherent heterogeneity of tide-dominated estuarine systems, where rapid lateral and vertical facies transitions, driven by fluctuating tidal energy and sediment supply, create complex reservoir architectures. Despite this complexity, the study demonstrates that higher-quality reservoir facies tend to preferentially accumulate in zones subjected to stronger tidal currents—specifically in the outer estuarine domain.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"182 ","pages":"Article 107581"},"PeriodicalIF":3.6,"publicationDate":"2025-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144842653","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Multi-scale characterization and control factors of bedding-parallel fractures in continental shale reservoirs: Insights from the Qingshankou Formation, Songliao Basin, China","authors":"Xiaocen Su ,&nbsp;Rukai Zhu ,&nbsp;Jingya Zhang ,&nbsp;Chang Liu ,&nbsp;Lei Gong ,&nbsp;Xiaohua Jiang ,&nbsp;Xiaofei Fu ,&nbsp;Mehdi Ostadhassan","doi":"10.1016/j.marpetgeo.2025.107580","DOIUrl":"10.1016/j.marpetgeo.2025.107580","url":null,"abstract":"<div><div>Bedding-parallel fractures play a critical role in enhancing storage capacity and horizontal permeability in tight shale reservoirs, significantly influencing the enrichment and productivity of shale oil. This study focuses on the continental shale of the Qingshankou Formation in the Songliao Basin, China, and systematically investigates the development characteristics and controlling factors of bedding-parallel fractures using a multi-scale dataset including core observations, image logs, scanning electron microscopy (SEM), and optical microscopy. Results show that bedding-parallel fractures are extensively developed across nano-to macro-scales, with nano-scale fractures reaching densities of up to 10⁵ fractures/m. Fracture density is negatively correlated with both fracture scale and aperture. These fractures are generally sub-parallel to bedding or exhibit low-angle orientations (mostly &lt;10°), and are typically discontinuous with limited lateral connectivity. Quantitative analyses indicate that fracture density is positively correlated with the contents of clay minerals, pyrite, and carbonate minerals, while showing weak or negative correlations with brittle minerals such as quartz and feldspar. Higher fracture densities are also observed in shales with elevated TOC content and higher thermal maturity. Furthermore, the type, thickness, and density of lamination significantly influence fracture development. At micro- and nano-scales, bedding-parallel fractures primarily act as hydrocarbon storage spaces and micro-flow conduits, whereas at the macro-scale, they mainly serve as horizontal flow pathways. These findings elucidate the multi-scale development mechanisms of bedding-parallel fractures in continental shale and underscore their dominant role in improving reservoir performance.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"182 ","pages":"Article 107580"},"PeriodicalIF":3.6,"publicationDate":"2025-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144826897","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}