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The Lower Cretaceous Laiyang Group on Lingshan Island contains typical gas source and clastic reservoir rocks. The densification mechanism of clastic rock and its diagenetic connection have not been systematically studied, which significantly increases the risk associated with hydrocarbon exploration in eastern China. A comprehensive study was conducted on core samples obtained from the Scientific Drilling Borehole LK-1, utilizing core data in conjunction with a range of techniques, including microscopic observation, X-ray diffraction, physical property measurements, and low-temperature nitrogen adsorption. The results indicate that the sandstones are primarily composed of feldspathic litharenite, exhibiting a poorly to moderately sorted texture and a fine-to-medium grain size. The reservoir quality is quite poor, characterized by extremely low porosity and permeability. The reservoir space of tight sandstones is constituted by three main types of pores: residual primary pores, secondary dissolution pores, and intercrystalline pores. Tight sandstone reservoirs experienced notable diagenetic alteration during burial, with calcite, dolomite, quartz, and clay cements identified as the primary diagenetic minerals. Intense compaction and carbonate cementation are the principal mechanisms contributing to the densification of sandstones. Pore-filling clay minerals subdivide macropores into numerous micropores, significantly reducing reservoir permeability. The migration of dissolution products out of the system is a difficult process, which hinders the effectiveness of mineral dissolution in enhancing overall reservoir quality. This study may provide a valuable reference for the effective exploration of Lower Cretaceous clastic reservoirs in eastern Shandong. [ABSTRACT FROM AUTHOR]

The breakthrough of bauxite natural gas in the Taiyuan Formation in the Longdong area of the Ordos Basin makes bauxite natural gas gradually become a new exploration direction. However, the complex sedimentary conditions and diverse developmental strata of the Linxing region present difficulties for the exploration of bauxite gas. In this research, samples of bauxite cores from significant drilling sections in the Linxing area were obtained for comprehensive geochemical, mineralogical, and pore structure analysis. This study investigates the impact of sedimentary environments on the physical properties of bauxite reservoirs within the Benxi Formation, focusing on lithofacies categorization, mineral composition, and pore structure. This study established a lithofacies categorization system that iron minerals, aluminum minerals + titanium minerals, clay minerals as three end‐member components. The study identified four lithofacies types: pure bauxite, clayey bauxite, mixed bauxite, and bauxite mudstone. According to geochemical analysis, the bauxite rock in the study area is deposited in a semi‐enclosed bay with terrestrial freshwater input. The physical properties of bauxite reservoir in the study area are relatively poor, among which the physical properties of bauxite reservoir are the best. Authigenic minerals like pyrite are often filled in dissolution pores. The constraint of sedimentary environment on bauxite reservoir is mainly manifested as the influence on the formation of diaspore mineral framework, and its acidity and alkalinity are very important for the formation of diaspore. Hence, diaspore commonly forms in the shallow lake environments characterized by pure bauxite rock, exhibiting favorable reservoir conditions. This research examines the impact of mineral composition on bauxite reservoirs through the lens of lithofacies and sedimentary environments. The variations in bauxite rock reservoirs across distinct sedimentary environments have been elucidated. It provides a new guidance for the exploration of natural gas in Benxi Formation bauxite in Ordos Basin. [ABSTRACT FROM AUTHOR]

The editorial discusses the differences in shale oil and gas reservoirs across various sedimentary environments, focusing on theories and applications. It highlights the significance of shale oil and gas as unconventional resources crucial for global energy optimization and carbon neutrality goals. The text explores the development of shale oil and gas in the United States and China, emphasizing technological advancements, resource estimates, and exploration efforts. Additionally, it delves into the characterization of shale pore structure, hydraulic fracturing techniques, and the influence of depositional environments on shale properties, providing valuable insights for future research and development in the field. [Extracted from the article]

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The seventh member of the Triassic Yanchang Formation (Chang 7 Member) in the Xunyi area of the Ordos Basin is a typical tight oil reservoir characterized by low porosity, low permeability, and strong heterogeneity. Elucidating the pore development characteristics and primary controlling factors of the reservoir is beneficial for tight oil exploration and development. Through thin-section analysis, physical property tests, scanning electron microscopy(SEM), X-ray diffraction (XRD) analysis, and mercury intrusion porosimetry, this study investigated the petrological characteristics, reservoir space, and diagenetic evolution of the tight oil reservoir, revealing its main controlling factors. The reservoir depth in Chang 7 Member of the Xunyi area of the Ordos Basin ranged from 500 to 1 250 m. The lithology was primarily composed of lithic arkose sandstone, followed by feldspar lithic sandstone, with the interstitial materials mainly consisting of calcite, dolomite, and mud. The sand bodies in the reservoir were thick, with high compositional maturity. Rigid minerals, such as quartz and feldspar, which are highly resistant to weathering, made up a large portion of the framework grains. The quartz content ranged from 30% to 77%, with an average of 44.97%, while the feldspar content ranged from 4% to 52%, with an average of 31.61%. The pore types were mostly intergranular dissolved pores and intragranular dissolved pores, followed by residual intergranular pores and a few microfractures. The average porosity was 7.3%, and the average permeability was 0.4×10-3 μm2. The reservoir is in the middle diagenetic stage A and has completed tight compaction during the Cretaceous. The primary factors contributing to reservoir densification included its poor resistance to compaction, carbonate cementation, illite/smectite mixed layers, and authigenic quartz. The quartz and feldspar content and early oil and gas charging preserved a significant quantity of primary pores. The ongoing dissolution and fragmentation during the middle diagenetic stage were the primary causes for the development of secondary pores.

The Jurassic Shaximiao Formation in the Sichuan Basin represents a significant tight gas reservoir, exhibiting marked permeability variations between the southern and northern regions of western Sichuan. This study examines the reservoir characteristics of the Shaximiao Formation, with a focus on the evolution of sandstone porosity under bidirectional provenance conditions and the underlying causes of permeability variations. The insights derived from this research are critical for the effective exploration and development of tight sandstone gas reservoirs. Analysis of core samples and thin sections through X-ray diffraction, cathodoluminescence, scanning electron microscopy, and electron probe microanalysis reveals that the southern region predominantly consists of feldspathic and lithic sandstone, whereas the northern region is characterized by feldspathic lithic and lithic feldspathic sandstone. The average porosity and permeability in the southern region are 10.52% and 0.1334 × 10−3 μm2, respectively, while in the northern region, they are 9.74% and 0.5262 × 10−3 μm2. The primary reservoir spaces are intergranular primary pores and intragranular secondary dissolution pores. Compaction significantly reduces porosity, particularly in the northern region (23.94%) compared to the southern region (22.75%), primarily due to the presence of chlorite coatings. Cementation further reduces porosity, whereas dissolution processes enhance it, elucidating the similar porosity values but differing permeabilities between the regions.

The Lower Ordovician Tongzi Formation containing abundant shoal sediments is the most promising stratum for the petroleum exploration in the Sichuan Basin. However, the current studies mainly focus on the central part of the Basin, the systematic analysis of the southeastern part with well-developed shoal facies is lacking. This paper aims to clarify the characteristics and genesis of the Tongzi Formation reservoir in Southeastern Sichuan Basin, following an analysis of sedimentary facies within the sequence stratigraphic framework. The research shows that the main types of reservoir rocks are oolitic, intraclastic and bioclastic dolostones. And the reservoir spaces consist mainly of intergranular (dissolved) pores, intercrystalline (dissolved) pores, intragranular dissolved pores and fractures. Among them, intergranular pores account for the highest proportion, which is followed by intragranular dissolved pores. In addition, most throats are necking and flaky which mainly connect intergranular and intercrystalline pores, respectively. The diagenetic sequence shows that penecontemporaneous karst well improved the porosity of the reservoir in the early-stage although the cementation and compaction reduced parts of pores. The reservoir formation is associated with the tectonic-depositional settings, diageneses and terrigenous contamination. Paleohighlands and submerged uplifts, forming in the early Ordovician amalgamation between Yangtze and Cathaysia blocks, accumulated shoal sediments as the material basis for the reservoir formation. Penecontemporaneous karst forming intragranular dissolved pores and the dolomitization aiding grainstones to resist the pressure solution are the key to increasing porosity and preserving pores. The absence of terrigenous contamination prevented intergranular pores from being strongly cemented, which resulted in the reservoir difference between the central and southeastern Sichuan Basin. The study can be used as a reference for the further exploration of Ordovician petroleum in the Sichuan Basin and other regions owning similar geological settings.

The exploration of the first member of Permian Maokou Formation (Maokou 1) in the Weiyuan area of southern Sichuan Basin has been limited. Previous analyses of cast thin sections and argon ion electron microscopy based on earlier drilling data suggested that talc pores were the primary reservoir spaces, with talc formation significantly contributing to the reservoir. However, the latest drilling data shows substantial differences in the types of reservoir spaces and the genesis of the Maokou 1 marlstone reservoirs compared to earlier understanding. It is necessary to further clarify the main controlling factors for the development of these reservoirs in the Maokou 1 member. Through core observation, thin section identification, physical property analysis, nitrogen adsorption, argon ion polishing scanning electron microscopy, and quantitative pore characterization, the primary reservoir spaces and types of the Maokou 1 marlstone were analyzed from both qualitative and quantitative perspectives. The main controlling factors for the development of these reservoirs were identified by combining total organic carbon (TOC) content determination, rare earth element analysis, and whole rock X-ray diffraction. High-quality reservoirs in the Maokou 1 member of the Weiyuan area are developed in marlstone, characterized by low porosity and permeability fractures and pore-type reservoirs, predominantly Type Ⅲ with some Type Ⅱ reservoirs. The main reservoir spaces include corroded pores, organic matter pores, and talc pores and fractures, with pore development closely related to TOC content. Talc formation, dolomitization, and silicification did not significantly contribute to secondary reservoir spaces, and their contribution to porosity is minimal. The development of marlstone reservoirs is jointly controlled by early dissolution, sedimentary facies, and organic matter abundance. Early dissolution is the key to the formation of corroded pores and fractures, while high primary productivity and high organic matter settling rate of the inner gentle slope shallow water environment provided the material basis for the formation of organic matter pores. This understanding provides theoretical support for the exploration of similar oil and gas reservoirs in the basin.

Based on an elaboration of the resource potential and annual production of tight sandstone gas and shale gas in the United States and China, this paper reviews the researches on the distribution of tight sandstone gas and shale gas reservoirs, and analyzes the distribution characteristics and genetic types of tight sandstone gas reservoirs. In the United States, the proportion of tight sandstone gas in the total gas production declined from 20%–35% in 2008 to about 8% in 2023, and the shale gas production was 8 310×108 m3 in 2023, about 80% of the total gas production, in contrast to the range of 5%–17% during 2000–2008. In China, the proportion of tight sandstone gas in the total gas production increased from 16% in 2010 to 28% or higher in 2023. China began to produce shale gas in 2012, with the production reaching 250×108 m3 in 2023, about 11% of the total gas production of the country. The distribution of shale gas reservoirs is continuous. According to the fault presence, fault displacement and gas layer thickness, the continuous shale gas reservoirs can be divided into two types: continuity and intermittency. Most previous studies believed that both tight sandstone gas reservoirs and shale gas reservoirs are continuous, but this paper holds that the distribution of tight sandstone gas reservoirs is not continuous. According to the trap types, tight sandstone gas reservoirs can be divided into lithologic, anticlinal, and synclinal reservoirs. The tight sandstone gas is coal-derived in typical basins in China and Egypt, but oil-type gas in typical basins in the United States and Oman.

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The geological storage of carbon dioxide (CO2) in offshore saline aquifers stands as a primary option for reducing CO2 emissions in coastal regions. China's coastal regions, particularly Shandong and Jiangsu provinces, face significant challenges in CO2 reduction. Therefore, evaluating the feasibility of CO2 geological storage in the adjacent seas is critical. To assess the suitability of a CO2 storage site, understanding its structural and reservoir characteristics is essential to mitigate injection and storage risks. In this study, we analyzed the structural characteristics and potential traps of the Yantai Depression in the South Yellow Sea Basin based on seismic data interpretation. We further conducted well logging analysis and post-stack seismic inversion to obtain lithological data, including acoustic impedance and sandstone content percentages from the Cenozoic Funing Formation, Dainan–Sanduo Formation, and Yancheng Formation. Our findings highlight that the Yantai Depression in the South Yellow Sea Basin exhibits diverse structural traps and favorable reservoir–caprock combinations, suggesting promising geological conditions for CO2 storage. This area emerges as a suitable candidate for implementing CO2 geological storage initiatives. [ABSTRACT FROM AUTHOR]

Recent exploration efforts have revealed significant industrial gas flow from the Wujiaping Formation marine shale in the Longmen-Wushankan area of the eastern Sichuan Basin, underscoring its considerable exploration potential. In this study, the reservoir characteristics and exploration potential of the Wujiaping Formation shale gas in this area are further evaluated. On the basis of well rock electrical properties, experimental analyses, and depositional and structural patterns in the eastern region, we characterize the reservoir properties and identify the primary factors controlling shale gas accumulation. The results indicate that the Wujiaping shale is characterized by a high organic matter content, favorable pore types, high porosity, and a high content of brittle minerals, which are conducive to subsequent development and fracturing. A positive correlation is observed between the total organic carbon (TOC) content, porosity, brittle mineral content, and shale gas content. The TOC content is strongly correlated with the gas content (the correlation coefficient is 0.75). The high shale gas yield of the Wujiaping Formation is attributed to a combination of favorable sedimentary environments, pore conditions, roof and floor conditions, and fracturing capabilities. However, compared with the Longmaxi Formation in the Sichuan Basin, the Wujiaping Formation shale is characterized by a lower porosity, thinner shale, and deeper burial, posing challenges for exploration and development. In this study, criteria for evaluating Wujiaping Formation shale gas are established, and four favorable exploration areas are identified. Overall, the Permian Wujiaping Formation marine shale in the Longmen-Wushankan area holds promising exploration and development potential. Further exploration and an enhanced understanding of this formation will provide valuable guidance for future marine shale gas exploration and development in this area. [ABSTRACT FROM AUTHOR]

As one of the most important future clean energy sources, natural gas hydrate (NGH) is attracting widespread attention due to the vast reserves available and high energy density. How to extract this source in a safe, efficient, and environmentally friendly manner has become the key to the commercial utilization of its resources. This paper reviews the recent advances in the study of the fundamental reservoir properties of offshore NGH, summarizing the methods and technologies for testing the sedimentary properties of reservoirs, analyzing the characteristics in reservoir mechanics, electrics, thermodynamics, and fluid dynamics, and discusses the influence of reservoir fundamental properties on NGH exploitation. The aim is to provide guidance and reference for research on the exploitation of NGH in different target exploitation areas offshore. [ABSTRACT FROM AUTHOR]

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Copyright of Acta Sedimentologica Sinica is the property of Acta Sedimentologica Sinica Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To further study the reservoir characteristics and adsorption capacity of the Taiyuan Formation shale in the South North China Basin (SNCB), the pore structure and adsorption capacity of shale are discussed using various analysis tests, including elemental geochemistry, organic geochemistry, mineral composition, low-temperature nitrogen adsorption (LTNA), and methane adsorption experiments. The results indicate that the Taiyuan Formation shale formed in a poor oxygen and anaerobic sedimentary environment in still water. The average value of total organic carbon (TOC) content is 2.37%. The organic matter type mainly consists of type III kerogen. The vitinite reflectance (Ro) ranges from 3.11% to 3.50%. The clay mineral content varies greatly, averaging at 40.7%, while the quartz content averages at 37.7%. The Taiyuan Formation shale mainly develops interparticle (InterP) pores, followed by organic pores, intraparticle (IntraP) pores, solution pores, and microfractures. BET specific surface area (SSA) is between 9.47 m2/g and 22.14 m2/g, while pore volume (PV) ranges from 0.0098 cm3/g to 0.022 cm3/g, indicating favorable conditions for shale gas storage. According to the results of the CH4 adsorption experiment, Langmuir volume from Taiyuan Formation shales exhibits 1.35~4.30 cm3/g, indicating excellent adsorption capacity. TOC content shows a positive correlation with both Langmuir volume and BET SSA from Taiyuan Formation shales, suggesting that TOC plays a crucial role in controlling microscopic pores and gas adsorption capacity. Organic matter enhances the shale adsorption capacity by providing abundant pore SSA. Due to formation compaction, the pore size of clay minerals decreases, leading to an increase in pore SSA, while kaolinite exhibits weak hydrophilic ability. Consequently, with the increase in clay minerals and kaolinite content, the shale adsorption capacity is enhanced to a certain extent. However, an increase in the carbonate mineral content may result in a decrease in the proportion of clay minerals, therefore reducing the CH4 adsorption capacity of shale. [ABSTRACT FROM AUTHOR]

Due to large burial depths， ultra-deep clastic rock reservoirs have poor physical properties and low oil and gas productivity. However， the newly drilled Well Zheng10 in Shawan Sag， Sinopec exploration area， has encountered high-quality thick reservoirs in the Triassic Karamay Formation at a buried depth of 6 700 m， and conventional tests have obtained high industrial oil and gas flow. To reveal the characteristics of this set of reservoirs and favorable main controlling factors， clarify the direction of ultra-deep clastic rock exploration， and reduce the risk of further oil and gas exploration in this area， this paper comprehensively analyzed the data of core， well logging， cast thin sections， physical properties， scanning electron microscopy， and diagenetic evolution of the reservoirs， and discussed the petrological， physical， and pore characteristics of reservoirs in the Triassic Karamay Formation in this area. The results show that the ultra-deep clastic rocks of the Triassic Karamay Formation in Well Zheng10 area are deposited in the front of the braided river delta. The lithology is dominated by glutenites， gravel-bearing fine sandstones， and fine sandstones， and the rock types are mainly feldspar lithic sandstones with low composition maturity. The remaining primary pores and solution pores dominate the reservoir space. The average porosity of the reservoirs is 9.1%， and the average permeability is 2.85 mD. The reservoir belongs to the ultra-low porosity and ultra-low permeability type and low porosity and low permeability type as a whole. Favorable sedimentary facies zones， constructive diagenesis， and abnormal high-pressure control the development and distribution of favorable reservoirs in this area. Among them， sedimentary microfacies are the basis of favorable reservoir development. The fine sandstones deposited in the underwater distributary channel at the front of the braided river delta are better sorted and rounded. The contents of the muddy matrix are low， and the physical properties of the reservoir are better， which are the dominant phase zones for favorable reservoir development. The sodium feldspar cements generated in the early diagenetic process are dissolved by acids in the later period， which increases the dissolution pores and is an essential constructive diagenesis. The abnormal high-pressures formed by continuous oil and gas charging form early and develop continuously for a long time， playing an important construction role. The research results have a guiding role for the subsequent ultra-deep oil and gas exploration in this area.

The Lower Cambrian Longwangmiao Formation in the Penglai gas area has promising carbonate reservoirs and exhibit strong gas indications, making itself a pivotal exploration zone following the Anyue gas field in the central Sichuan region. However, the lack of clarity regarding reservoir development patterns has constrained exploration deployment. Through comprehensive analysis of the most recent drilling and testing data, this study systematically examines the reservoir characteristics and primary controlling factors of the Longwangmiao Formation in Penglai gas area. Results reveal a mixed sedimentary background of terrigenous debris and carbonate, with reservoirs predominantly situated in the middle and upper strata of the Longwangmiao Formation. The reservoir rock types are predominantly (residual) granular dolomite and crystalline dolomite. Main types of reservoir space include intergranular dissolved pores, intragranular dissolved pores, intercrystalline dissolved pores, and micro-fractures. The reservoir is characterized by low porosity and permeability, with thickness typically ranging between 10-42 m. Reservoir development is controlled by sequence stratigraphy, lithology and diagenesis, particularly evident in the granular dolomite and crystalline dolomite within the middle and upper sections of the progradational parasequence set. Key constructive diagenetic processes include atmospheric freshwater dissolution, oil and gas dissolution and fracture. A comparison with the Moxi-Gaoshiti area in the main area of Anyue gas field suggests similar controlling factors, primarily revolving around granular dolomite, dissolution and fracturing. Nonetheless, the Longwangmiao Formation reservoir in Penglai gas area exhibit distinctive traits such as high ash content, elevated terrigenous clastic content and limited penecontemporaneous exposure. Consequently, identifying high-energy granular dolomite and fine-grained dolomite exposed during the penecontemporaneous period, as well as dolomite modified by supergene karst, emerges as imperative in targeting reservoirs within the Penglai gas area.

In order to explore the strong heterogeneity of evaporite-carbonate symbolic system, based on core and logging data, this paper clarifies microfacies types of Arab Formation in B Oilfield of Abu Dhabi, and analyzes the reservoir characteristics of various microfacies and the main controlling factors of high-quality reservoirs. Twelve microfacies types (MF1--MF12) can be identified in the Arab Formation. Microfacies types and associations indicate that it is a sedimentary system of Sabha tidal flat-lagoon-barrier beach under the background of limited-evaporation. Microfacies control reservoir quality. MF2 and MF9--MF12 have thicker pore throats, better connectivity, and higher porosity and permeability, making them favorable microfacies types for reservoir development. MF2 and MF10 develop dolomite reservoirs, with the reservoir space mainly composed of intergranular pores, residual intergranular pores and intragranular dissolution pores. Grainstone reservoirs are developed in MF9, MF11 and MF12, with the reservoir space dominated by intergranular (dissolution) pores, mold pores and intragranular dissolution pores. The seismic change of relative sea level causes orderly stacking of sedimentary facies belts in longitudinal direction. The difference of microfacies types and diagenesis between different sedimentary facies belts and within the same sedimentary facies belt is the fundamental reason for the strong heterogeneity of the Arab Formation reservoir. The barrier beach and supratidal are favorable facies belts for the development of high-quality reservoirs. The primary intergranular pores of high-quality reservoirs in the barrier beach facies are well maintained and superimposed with significant early exposure and dissolution, resulting in the generation of secondary pores and the further improvement of pore structure. The development of high-quality reservoirs in the supratidal is controlled by early dolomitization and penecontemporaneous dissolution. Dolomitization improves pore structure, which is conducive to early pore preservation. The early dissolution of dispersed anhydrite produces a large number of secondary pores, significantly improving reservoir physical properties. [ABSTRACT FROM AUTHOR]

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Wenchang A oilfield is a recently discovered low-permeability oilfield in the western South China Sea. The exploration target is the Zhuhai Formation, which reservoir lithology changes significantly, and the distribution of favorable reservoirs is unclear. In this study, the reservoir characteristics of the Zhuhai Formation in the Wenchang A oilfield, South China Sea, were analyzed through core identification, thin section identification, physical property testing, prestack geostatistical inversion, and frequency-based AVO inversion. Pre-stack geostatistical inversion is based on geostatistics and combines the seismic inversion algorithm with the stochastic sequential simulation algorithm. While the frequency-varying AVO inversion method is an extension of the conventional AVO inversion method, with its core technology being spectrum decomposition. After frequency division, multiple data sets directly participate in the calculation, which enhances the stability and accuracy of inversion.We also predict the favorable reservoir areas of six small layers in the Zhuhai Formation. The results show that 1) the reservoir lithology of the Zhuhai Formation mainly consists of feldspar quartz sandstone and feldspar quartz sandstone, indicating high compositional maturity. The porosity of the reservoir ranges from 14.0% to 19.0%, with an average value of 16.3%. The permeability of the reservoir ranges from 3.1 mD to 126.1 mD, with an average value of 22.4 mD, indicating a medium porosity and low permeability reservoir. The supporting structure of a sandstone reservoir is particle-supported, with the main contact being the "point-line" contact between particles. The main types of pores in sandstone are primary intergranular pores and secondary intergranular dissolved pores. Some pores are feldspar-dissolved pores, and occasionally there are hetero-based micropore. 2) The diagenesis of the Zhuhai Formation reservoir mainly includes compaction, cementation, and dissolution. Cementation and dissolution have minimal impact on the physical properties of reservoirs. The porosity loss of the reservoir after compaction ranges between 16.0% and 27.9%, and the compaction rate ranges between 40.0% and 69.8%, indicating a medium compaction diagenetic facies. 3) The favorable areas of each layer of the Zhuhai Formation are mainly concentrated in the southwest of the study area. The upper layer of ZH1I, the upper layer of ZH1II and the lower layer of ZH1II exhibit the best physical properties, the thickest favorable sand body, the strongest oil and gas display, the widest range of favorable areas, and the greatest exploration potential. The favorable exploration potential of layer 1 in the lower part of ZH1I and layer 2 in the upper part of ZH1II is moderate. The second layer in the lower part of ZH1II has the poorest properties and lower exploration potential. The main factors affecting the favorable area include physical properties, oil and gas display, sand body thickness, etc. [ABSTRACT FROM AUTHOR]

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Reservoir characterization is an important component of hydrocarbon exploration and production, which requires the integration of different disciplines for accurate subsurface modeling. This comprehensive research paper delves into the complex interplay of rock materials, rock formation techniques, and geological modeling techniques for improving reservoir quality. The research plays an important role dominated by petrophysical factors such as porosity, shale volume, water content, and permeability—as important indicators of reservoir properties, fluid behavior, and hydrocarbon potential. It examines various rock cataloging techniques, focusing on rock aggregation techniques and self-organizing maps (SOMs) to identify specific and anomalous rock faces. Furthermore, the paper explores the adoption of advanced methods, including hydraulic flow units (HFU), providing a fine-grained understanding of reservoir heterogeneity and contributing to the prediction of flow dynamics. The final section includes structural geological models, petrophysical data collected, rock type classification, and spatial data to better represent the reservoir bottom structure. It provides a valuable resource for researchers, geologists, and engineers seeking to characterize reservoirs and make optimal decisions on hydrocarbon exploration and production. It is an important component of hydrocarbon exploration and production, which requires the integration of different disciplines for accurate subsurface modeling.

Recent exploration efforts have revealed significant industrial gas flow from the Wujiaping Formation marine shale in the Longmen–Wushankan area of the eastern Sichuan Basin, underscoring its considerable exploration potential. In this study, the reservoir characteristics and exploration potential of the Wujiaping Formation shale gas in this area are further evaluated. On the basis of well rock electrical properties, experimental analyses, and depositional and structural patterns in the eastern region, we characterize the reservoir properties and identify the primary factors controlling shale gas accumulation. The results indicate that the Wujiaping shale is characterized by a high organic matter content, favorable pore types, high porosity, and a high content of brittle minerals, which are conducive to subsequent development and fracturing. A positive correlation is observed between the total organic carbon (TOC) content, porosity, brittle mineral content, and shale gas content. The TOC content is strongly correlated with the gas content (the correlation coefficient is 0.75). The high shale gas yield of the Wujiaping Formation is attributed to a combination of favorable sedimentary environments, pore conditions, roof and floor conditions, and fracturing capabilities. However, compared with the Longmaxi Formation in the Sichuan Basin, the Wujiaping Formation shale is characterized by a lower porosity, thinner shale, and deeper burial, posing challenges for exploration and development. In this study, criteria for evaluating Wujiaping Formation shale gas are established, and four favorable exploration areas are identified. Overall, the Permian Wujiaping Formation marine shale in the Longmen–Wushankan area holds promising exploration and development potential. Further exploration and an enhanced understanding of this formation will provide valuable guidance for future marine shale gas exploration and development in this area.

The Fuxing area of the Sichuan Basin is known for its multiple sets of organic-rich shale in the Jurassic period, with several wells yielding significant amounts of industrial oil and gas. Understanding the characteristics and factors influencing the enrichment of different shale facies sedimentary reservoirs is crucial for effective exploration. Through detailed rock core descriptions, experimental analysis, and drilling exploration, the author has classified and compared fine-grained sedimentary rock facies in terrestrial strata, characterized reservoirs, identified types of oil and gas reservoirs, and analyzed the main factors influencing enrichment and productivity. The study reveals that the Jurassic strata in the Fuxing area contain two sets of high-quality shale with semi-deep lacustrine facies: the first sub-section of the Dongyuemiao section of the Ziliujing Formation and the lower sub-section of the second section of the Lianggaoshan Formation. These shale layers exhibit multi-layer stacking, moderate TOC content, well-developed bedding, integrated source storage, and high gas/oil ratio characteristics. The lithology of these target shale layers is complex, leading to the establishment of a four-element lithofacies classification scheme based on "color-TOC-sedimentary structure-mineral composition". This scheme identifies the gray-black high carbon sand-laminated clay shale as the favorable lithofacies for the lower sub-section of the second section of the Lianggaoshan Formation, and the gray-black high carbon medium debris-laminated and fine sand medium debris-laminated clay shale as the favorable lithofacies for the eastern sub-section. The three lithofacies in the study area are horizontally distributed in a stable manner. The gray-black high carbon fine sand layer, medium debris layer, and fine sand-medium debris layer type clay shale exhibit reservoir characteristics of "porous coexistence, large pores and throats, and integrated pores and fractures". These reservoir properties, including good permeability, facilitate the efficient storage and flow of shale oil and gas in the pore-fracture storage system. The first sub-section of the Dongyuemiao section is a condensate gas reservoir, while the lower sub-section of the Lianggaoshan Formation's second section is a volatile oil reservoir. Key factors contributing to the enrichment of continental shale oil and gas have been identified, including medium to high hydrocarbon generation potential and strong retention rates supporting the accumulation of laminated shale oil and gas. A favorable hydrocarbon-diagenesis-reservoir formation configuration promotes oil and gas accumulation. Additionally, the development of micro cracks and suitable thermal evolution aids in hydrocarbon enrichment and flow, while large, wide, gentle synclines and high-pressure overpressure conditions support the sustained preservation of hydrocarbons.

Objective The main controlling factors and densification genesis of sandstone reservoirs around the paleo-uplift in the southern Tianshan area of the Tarim Basin have always restricted the increase in reserves and production in this area. Methods By using thin section and cathode luminescence (CL) observations, physical property testing, mercury injection analysis, and other related methods, the characteristics of sandstone reservoirs in the Lower Cretaceous Baxigai and Shushanhe Formations were studied, and the main factors controlling the reservoir properties were also summarized. Results The study draws the following conclusions: The porosity of the target layer in the study area is mostly less than 10%, and the permeability is less than 1×10-3 μm2, which is a typical tight sandstone reservoir. Among them, the braided river delta sandstones exhibit the best physical properties (φ=12.3%, k=60.4×10-3 μm2) and pore structure, followed by the fan delta sandstones (φ=6.9%, k=1.9×10-3 μm2), while the lacustrine sand bar facies features the worst physical properties (φ=6.7%, k=0.34×10-3 μm2). The evolution of paleo-uplift controlled the differences between sedimentary facies and diagenetic processes. The sedimentary environment of braided river deltas and fan deltas has strong hydrodynamic forces, coarser particles, and weak cementation, so the porosity and permeability are high. In contrast, the lacustrine sand bar facies are far away from terrigenous input, the grains are fine, and the underwater paleo-uplift controlled the formation of carbonate cement with high contents in the diagenetic stage, which blocked the pore throat and reduced the physical properties of the sandstone reservoir. Conclusion These results provide a reference for petroleum exploration and development of the Lower Cretaceous successions in the southern Tianshan area.

Through core observation, thin section identification, X-ray diffraction analysis, scanning electron microscopy, and low-temperature nitrogen adsorption and isothermal adsorption experiments, the lithology and pore characteristics of the Upper Carboniferous bauxite series in eastern Ordos Basin were analyzed to reveal the formation and evolution process of the bauxite reservoirs. A petrological nomenclature and classification scheme for bauxitic rocks based on three units (aluminum hydroxides, iron minerals and clay minerals) is proposed. It is found that bauxitic mudstone is in the form of dense massive and clastic structures, while the (clayey) bauxite is of dense massive, pisolite, oolite, porous soil and clastic structures. Both bauxitic mudstone and bauxite reservoirs develop dissolution pores, intercrystalline pores, and microfractures as the dominant gas storage space, with the porosity less than 10% and mesopores in dominance. The bauxite series in the North China Craton, which can be divided into five sections, i.e., ferrilite (Shanxi-style iron ore, section A), bauxitic mudstone (section B), bauxite (section C), bauxite mudstone (debris-containing, section D) and dark mudstone-coal section (section E). The burrow/funnel filling, lenticular, layered/massive bauxite deposits occur separately in the karst platforms, gentle slopes and low-lying areas. The karst platforms and gentle slopes are conducive to surface water leaching, with strong karstification, well-developed pores, large reservoir thickness and good physical properties, but poor strata continuity. The low-lying areas have poor physical properties but relatively continuous and stable reservoirs. The gas enrichment in bauxites is jointly controlled by source rock, reservoir rock and fractures. This recognition provides geological basis for the exploration and development of natural gas in the Upper Carboniferous in the study area and similar bauxite systems.

To facilitate the efficient exploration and development of coalbed methane of the Longtan Formation in the Guxu coal mining area, Sichuan, it is essential to evaluate the reservoir characteristics of the main production layers. In this study, scanning electron microscopy, low-temperature liquid nitrogen adsorption experiments, high-pressure mercury pressure experiments, and isothermal adsorption experiments were conducted to investigate the reservoir characteristics of favorable coalbed methane reservoirs. The results indicate that the main coal seams in the Longtan Formation are medium-to-high ash content anthracite with a well-developed pore–fracture system. The pore size distribution exhibits both unimodal and bimodal types, while the pore morphology includes impermeable pores closed at one end, open permeable pores, and ink bottle-shaped pores. It shows that the middle part of Longtan Formation acts as an enrichment zone for coalbed methane, which is characterized by a stronger adsorption capacity, high Langmuir volume, high gas content, and high gas saturation distribution. The pH value, mineralization degree, and hydrogen–oxygen isotope of the produced water in the main coal seams indicate that the enrichment zone is typically located in a stagnant flow zone with a reducing environment and favorable storage conditions. [ABSTRACT FROM AUTHOR]

The complexity and heterogeneity of pore structures in carbonate reservoirs pose significant challenges for accurately characterizing the influence of different pore micro-parameters on reservoir physical properties. Drawing upon the principles of fractal geometry theory applied to reservoir rocks, this study combines mercury intrusion porosimetry (MIP) and nuclear magnetic resonance (NMR) T2 spectrum methods to explore the relationship between the fractal dimension and micro-parameters of pore throats at various scales. Additionally, it clarifies how the fractal dimension of pores at different scales impacts reservoir physical properties. Moreover, a permeability prediction model that incorporates fractal dimensions is developed. The findings demonstrate that the fractal dimension effectively captures the complexity and multi-scale nature of reservoir microstructures, leading to higher reliability in predicting permeability when using the model incorporating the fractal dimension. It provides a theoretical basis for predicting the absolute permeability of fractured carbonate rocks in dual media. [ABSTRACT FROM AUTHOR]

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In current energy structure adjustments, the prominence of unconventional oil and gas resources continues to grow, with increasing attention being paid to tight gas, a major component of natural gas production. The Xujiahe Formation gas reservoir in the Western Sichuan Depression represents a typical tight gas reservoir and the study of its reservoir characteristics is a key focus for current and future exploration and development efforts. This review employs the PRISMA method to screen and integrate the primary findings of 26 documents spanning the period from 2008 to 2023, with the aim of providing a comprehensive overview of the progress and outcomes of research on the tight gas reservoir characteristics of the Xujiahe Formation in the Western Sichuan Depression. The selected research documents summarize the characteristics of the Xujiahe Formation tight gas reservoir in the Western Sichuan Depression from four perspectives: lithology, physical properties, reservoir space, and the main factors influencing reservoir quality. Through a review of these previous studies, it is evident that existing research has predominantly focused on the relationship between diagenesis and reservoir densification, indicating certain limitations. We also delve into the characteristics of tight gas sandstone reservoirs in the study area, considering their depositional systems, fracture development, cementation, and impact on the exploration and development of tight gas reservoirs. Additionally, we propose measures to stabilize and enhance tight gas production in the Xujiahe Formation in the Western Sichuan Depression. Moreover, we outline the next steps for further research and exploration. [ABSTRACT FROM AUTHOR]

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Copyright of Coal Geology & Exploration is the property of Xian Research Institute of China Coal Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Wenchang A oilfield is a recently discovered low-permeability oilfield in the western South China Sea. The exploration target is the Zhuhai Formation, which reservoir lithology changes significantly, and the distribution of favorable reservoirs is unclear. In this study, the reservoir characteristics of the Zhuhai Formation in the Wenchang A oilfield, South China Sea, were analyzed through core identification, thin section identification, physical property testing, pre-stack geostatistical inversion, and frequency-based AVO inversion. Pre-stack geostatistical inversion is based on geostatistics and combines the seismic inversion algorithm with the stochastic sequential simulation algorithm. While the frequency-varying AVO inversion method is an extension of the conventional AVO inversion method, with its core technology being spectrum decomposition. After frequency division, multiple data sets directly participate in the calculation, which enhances the stability and accuracy of inversion.We also predict the favorable reservoir areas of six small layers in the Zhuhai Formation. The results show that 1) the reservoir lithology of the Zhuhai Formation mainly consists of feldspar quartz sandstone and feldspar quartz sandstone, indicating high compositional maturity. The porosity of the reservoir ranges from 14.0% to 19.0%, with an average value of 16.3%. The permeability of the reservoir ranges from 3.1 mD to 126.1 mD, with an average value of 22.4 mD, indicating a medium porosity and low permeability reservoir. The supporting structure of a sandstone reservoir is particle-supported, with the main contact being the “point-line” contact between particles. The main types of pores in sandstone are primary intergranular pores and secondary intergranular dissolved pores. Some pores are feldspar-dissolved pores, and occasionally there are hetero-based micropore. 2) The diagenesis of the Zhuhai Formation reservoir mainly includes compaction, cementation, and dissolution. Cementation and dissolution have minimal impact on the physical properties of reservoirs. The porosity loss of the reservoir after compaction ranges between 16.0% and 27.9%, and the compaction rate ranges between 40.0% and 69.8%, indicating a medium compaction diagenetic facies. 3) The favorable areas of each layer of the Zhuhai Formation are mainly concentrated in the southwest of the study area. The upper layer of ZH1I, the upper layer of ZH1II and the lower layer of ZH1II exhibit the best physical properties, the thickest favorable sand body, the strongest oil and gas display, the widest range of favorable areas, and the greatest exploration potential. The favorable exploration potential of layer 1 in the lower part of ZH1I and layer 2 in the upper part of ZH1II is moderate. The second layer in the lower part of ZH1II has the poorest properties and lower exploration potential. The main factors affecting the favorable area include physical properties, oil and gas display, sand body thickness, etc.

To further guide the exploration and development of shale oil in the Da'anzhai Member of the Jurassic Ziliujing Formation in the Sichuan Basin, it is urgent to clarify the favorable lithofacies of shale oil. In this study, core observation, thin section authentication, high pressure mercury injection, NMR, rock pyrolysis analysis and other experiments were used to analyze the reservoir space types, pore structure characteristics and oil-bearing properties of different lithofacies of shale series in the Da'anzhai Member. The results show that mainly six types of lithofacies are developed in the Da'anzhai Member: massive (argillaceous) shell limestone, layered argillaceous shell limestone, layered shell shale, laminar shell-bearing shale, massive shell-bearing clay shale and foliated siltstone-bearing clay shale. The physical properties of shale in the Da'anzhai Member are much better than those of shell limestone, and with the increase of calcareous content, the pore size of the shale gradually increases, but the total pore volume and total connected volume gradually decrease. The average free oil value (S1) of the shale series in the Da'anzhai Member is 1.31 mg/g, with moderate oil-bearing property. The S1 values of the foliated siltstone-bearing clay shale and the laminar shell-bearing shale are relatively higher, which are 2.37 mg/g and 1.82 mg/g, respectively. In summary, it is believed that the foliated siltstone-bearing clay shale and the laminar shell-bearing shale have good reservoir properties and high oil-bearing properties. The lithofacies combination of the two can be a key exploration target for shale oil in the Da'anzhai Member.

The geological storage of carbon dioxide (CO2) in offshore saline aquifers stands as a primary option for reducing CO2 emissions in coastal regions. China’s coastal regions, particularly Shandong and Jiangsu provinces, face significant challenges in CO2 reduction. Therefore, evaluating the feasibility of CO2 geological storage in the adjacent seas is critical. To assess the suitability of a CO2 storage site, understanding its structural and reservoir characteristics is essential to mitigate injection and storage risks. In this study, we analyzed the structural characteristics and potential traps of the Yantai Depression in the South Yellow Sea Basin based on seismic data interpretation. We further conducted well logging analysis and post-stack seismic inversion to obtain lithological data, including acoustic impedance and sandstone content percentages from the Cenozoic Funing Formation, Dainan–Sanduo Formation, and Yancheng Formation. Our findings highlight that the Yantai Depression in the South Yellow Sea Basin exhibits diverse structural traps and favorable reservoir–caprock combinations, suggesting promising geological conditions for CO2 storage. This area emerges as a suitable candidate for implementing CO2 geological storage initiatives.

Tight limestone reservoirs in the Permian Taiyuan Formation of the Ordos Basin have garnered increasing attention in recent years, emerging as a pivotal domain in the quest for natural gas exploration. This research delves into the comprehensive investigation of petrology, reservoir space, reservoir physical properties, and microscopic characteristics through the examination of field outcrops, core observations, thin section identification, scanning electron microscopy, stable carbon and oxygen isotope analysis, and testing. The systematic analysis focused on elucidating the development characteristics of these reservoirs and identifying the controlling factors governing favorable reservoir conditions. Based on our research analysis, the specific rock types with the potential to serve as excellent reservoirs, includes bioclastic silty limestone, bioclastic micrite limestone, and algal-rich limestone. The predominant reservoir spaces within these formations were found to consist of dissolved pores, residual bioclastic cavity pores, intercrystalline pores, and microfractures. These reservoirs exhibit an average porosity of 2.1%, and an average permeability of 0.22 × 10−3 μm2, indicating their classification as low porosity and low permeability reservoirs. The formation of favorable reservoirs in the Taiyuan Formation limestone was determined to be influenced by many factors; notably, the favorable sedimentary microfacies associated with bioclastic shoals and bioherms provided the foundational material basis for the formation of reservoirs, influencing the type of reservoir space and its extensive planar distribution. Penecontemporaneous karstification, guided by high-frequency cycles, was favorable for the formation of dissolution holes, effectively improving reservoir performance and facilitating the development of thick limestone reservoirs. Furthermore, fractures were identified as crucial agents in improving the seepage capacity of these tight limestone reservoirs. Drawing from our research results, this study offers valuable guidance for the future exploration of limestone formations in the Taiyuan Formation in the Ordos Basin. Additionally, these findings hold considerable significance as a reference point for research and exploration endeavors focused on bioclastic limestone reservoirs in the North China Platform.

Since 2002, the Upper Cretaceous Abu Roash (G) Member in the Karama Oil Field has been considered to be one of the most important reservoirs in the Abu Gharadig Basin in the North‐Western Desert. This member is located in the Karama Oil Field. For the purpose of increasing oil production, a three‐dimensional reservoir model was developed, and the area's oil resource was determined by employing thirty two‐dimensional seismic lines dispersed in the north–south and east–west directions, in addition to five well logs. Within the Abu Roash Formation, which conformably overlies the Bahariya Formation and unconformably underlies the Khoman Formation, there are seven normal faults that allow for three‐way dip closure for oil accumulation. These faults cut through the Abu Roash Formation. The Abu Roash (G) Member is mostly composed of limestone, shale and intercalated siltstone and sandstone, and it ranges in thickness from 54 to 168 feet (16.5 to 51.2 m) in terms of its net pay. Effective porosity ranges anywhere from 20% to 30%, shale content can be anywhere from 13% to 24%, water saturation can be anywhere from 40% to 55% and hydrocarbon saturation can be as high as 60%. Through the integration of the constructed structural and property models, two new prospect areas have been presented (in the northern part of the study area). In these areas, the petrophysical parameters are good, and the Original oil in place (OOIP) is predicted to be 1107 × 106 Stock Tank Barrels (STB), which will help with the development plans for the study area. [ABSTRACT FROM AUTHOR]

This study takes the tuff reservoir of the Huoshiling Formation in the Dehui Fault Depression, Songliao Basin, as an example to clarify the characteristics and primary controlling factors of tuff reservoirs. 3D seismic, core, image log, thin section, production dynamic and other data were used. Mineral x‐ray diffraction, core computerized tomography scanning, high‐pressure mercury injection, porosity, permeability, scanning electron microscopy, cathodoluminescence thin section, element testing and other experiments were conducted. The volcanic rocks in the study area are divided into andesite, volcanic breccia, lithic tuff and crystal tuff. The experiment results show that the mineral composition of tuff is primarily quartz, feldspar and clay minerals. The reservoir space comprises secondary pores and fractures, whereas primary pores are not developed. Average pore‐throat radius of most samples ranges from 0.017 to 0.131 μm, and the pore‐throat is primarily fine. The average porosity is 12.21% (a typical medium‐high porosity reservoir), and the average permeability is 0.072 mD (an extra‐low permeability reservoir). Tectonic fractures generated by tectonic movement are one of the reservoir spaces of tuff. Faults and tectonic fractures constitute a crucial migration channel of the fluid in the deep stratum. The tuff formed in the underwater environment, and the reservoir is affected by alteration. Devitrification is a crucial cause of medium‐high porosity and ultra‐low permeability in reservoirs. The alteration caused by hydrothermal fluid in deep fluids creates a considerable number of pores and fractures filled with clay minerals. Furthermore, acid fluid dissolves tuff along faults and fractures. In terms of time, the filling action is earlier than the dissolution action. The weathering indexes of CIA, CIW, PIA and WIP indicate that the tuff has suffered intense weathering, and the reservoir's physical properties have been improved to some extent. [ABSTRACT FROM AUTHOR]

The Lower Silurian Longmaxi Formation is the favorable target area for deep shale gas exploration and development in southeastern Sichuan Basin. Based on whole-rock X-ray diffraction analysis, scanning electron microscope, reservoir evolution thermal simulation experiment and nitrogen adsorption experiment, the diagenetic characteristics of deep shale reservoir in Longmaxi Formation were analyzed, and the reservoir pore evolution law was clarified. The results show that: ①The diagenetic minerals of the deep shale in the Longmaxi Formation are mainly quartz and clay minerals, with a small amount of carbonate minerals and feldspar. The primary inorganic pores are mainly controlled by mechanical compaction and cementation (quartz, carbonate, clay, pyrite). The organic pores are mainly controlled by the thermal maturity of organic matter, dissolution and later compaction. ②In the process of thermal simulation experiment, the organic pores of shale show a process of change from scratch, from small to large and then from large to small. Later, the organic matter is affected by compaction and graphitization, and the volume of micropores and mesopores begins to decrease. ③The shale pores of Longmaxi Formation have undergone several evolutionary stages. In the early stage of diagenesis, compaction caused a large number of inorganic pores to disappear. In the middle stage of diagenesis, kerogen hydrocarbon generation occupied pores, dissolution and cementation transformed pores. In the late diagenetic period, liquid hydrocarbon cracking gas and pressurization promote the development of organic pores. [ABSTRACT FROM AUTHOR]

The present study carries out the sedimentological and diagenesis impact on reservoir quality of the Early Jurassic sandstone (Datta Formation) of Trans-Indus Ranges, Pakistan. To fulfill the objectives of the present study Pezu & Abbo Wanda sections have been selected. To evaluate the reservoir characteristics the thin section analysis, scanning electron microscope (SEM), SEM, cathodoluminescence (CL), X-ray diffraction (XRD), and core plug porosity and permeability analysis have been used. Field evidence shows that there are four depositional facies six lithofacies, and three microfacies, with different sedimentary structures, were observed, which indicates that Jurassic sandstone has been deposited in a deltaic environment. Petrographic analysis and SEM show compaction is moderate to high, and grain binding calcite cement with subordinate quartz overgrowth and hematite. Feldspar dissolution and clay minerals precipitation were important diagenetic reactions that influenced the quality of the reservoir. Primary intergranular pores, fractured, and dissolution pores are present within the studied sections. Overall, pores connectivity is good, and at some places, the quality of the pores has been affected by authigenic clay minerals. SEM analysis predicts that clay minerals like kaolinite, smectite, and Illite/smectite are common pore-filling minerals that reduce the reservoir quality. Primary pores, fractures, dissolution pores, as well as core plug porosity and permeability data (porosity 15.90 to 27.01% and permeability 0.15 to 150 mD) predict that Jurassic sandstone has good reservoir characteristics. [ABSTRACT FROM AUTHOR]

Unconventional reservoirs, including gas shales and tight gas sands, have gained prominence in the energy sector due to technological advancements and escalating energy demands. The oil industry is eagerly refining techniques to decipher these reservoirs, aiming to reduce data collection costs and uncertainties in reserve estimations. Characteristically, tight reservoirs exhibit low matrix porosity and ultra-low permeability, necessitating artificial stimulation for enhanced production. The efficacy of the stimulation hinges on the organic material distribution, the rock's mechanical attributes, and the prevailing stress field. Comprehensive petrophysical analysis, integrating standard and specialized logs, core analyses, and dynamic data, is pivotal for a nuanced understanding of these reservoirs. This ensures a reduction in prediction uncertainties, with parameters like shale volume, porosity, and permeability being vital. This article delves into an intricate petrophysical evaluation of the Nene field, a West African unconventional reservoir. It underscores the geological intricacies of the field, the pivotal role of data acquisition, and introduces avant-garde methodologies for depth matching, rock typing, and the estimation of permeability. This research highlights the significance of unconventional reservoir exploration in today's energy milieu, offering a granular understanding of the Nene field's geological challenges and proffering a blueprint for analogous future endeavours in unconventional reservoirs. [ABSTRACT FROM AUTHOR]

Nearly 100 million tons of reserves have been explored in the Well 471 area of the Hongche Fault zone. The Carboniferous volcanic rock reservoir is the main oil-bearing reservoir in the well CH471 area and is the main target of exploration and development. The characteristics of the Carboniferous volcanic rock reservoir are studied through core, thin section, physical property, logging, and other data, and its main controlling factors are analyzed in combination with actual means of production. The lithologies of the volcanic reservoir in the study area are mainly volcanic breccia, andesite, and basalt. The matrix physical properties of volcanic rock reservoirs are medium-porosity and ultralow-permeability, among which volcanic breccia has the best physical properties. The reservoir space mainly comprises primary pores, secondary dissolution pores, and fractures, resulting in a dual medium pore-fracture-type reservoir. Combined with production data analysis, the lateral distribution of oil and gas is controlled by lithology and lithofacies, with explosive volcanic breccia being the best, followed by the basalt and andesite of overflow facies, which are vertically affected by weathering and leaching and distributed within 50~300 m from the top of the Carboniferous system. The area with densely developed fractures was conducive to developing high-quality reservoirs. The tectonic movement promoted the formation of weathering and controlled the development of faults. Based on a comprehensive analysis, it is believed that the formation of Carboniferous volcanic oil and gas reservoirs in the study area was controlled and influenced by the lithology, lithofacies, weathering, leaching, faults (fractures), and tectonics. [ABSTRACT FROM AUTHOR]

Recent exploration practice shows that the leopard porphyry dolomite reservoir in the fourth member of Ordovician Majiagou Formation in the central and eastern Ordos Basin has good exploration and development potential. Therefore, based on drilling cores, rock slices and analysis and laboratory data, the reservoir characteristics and main controlling factors of this section were analyzed. The results show that: (1) The reservoir rocks of the fourth member of Majiagou Formation mainly include leopard porphyry dolomitic limestone, leopard porphyry limy dolomite, crystalline dolomite and clotted dolomite, and the reservoir space types mainly consist of intergranular (dissolution) pores, with a small amount of lattice pores and microcracks. (2) The reservoir in the study area is generally characte-rized by low porosity and medium-low permeability pore type reservoir, in which leopard porphyry limestone dolomite and crystalline dolomite are the best reservoir rocks with wide distribution range. However, leopard porphyry dolomitic limestone is developed on a large scale, with poor reservoir performance as a whole, while clotted dolomite has good reservoir performance, but its development frequency is low. The reservoir development in the fourth member of Majiagou Formation in the central and eastern Ordos Basin is mainly controlled by sedimentary microfacies, bioturbation, dolomitization and early diagenetic karstification: as the material basis for reservoir formation, favorable sedimentary microfacies control the horizontal distribution of reservoirs; bioturbation is for dolomitization; dolomitization is the key to reservoir formation, which is conducive to the preservation of reservoir pores; early diagenetic karstification has an important contribution to the improvement of reservoir quality. In the longitudinal, the favorable reservoirs in the fourth member of Majiagou Formation are mainly located in the middle-upper part of the high-frequency upward shallowing sequence; on the plane, the favorable reservoirs are mainly concentrated in the line of Wushen Banner-Jingbian-Zhidan in the west and the two relatively independent areas of Shenmu and Mizhi in the east of the study area.

The Middle Permian Maokou Formation in the Sichuan Basin is an important natural gas payzone. Recently, Zhejiang Oilfield Company of CNPC obtained industrial gas flow of vertical well test 42×103 m3/d and horizontal well (well DB 1H) test 556×103 m3/d in the limy source rock gas reservoir of eyelid and eyeball- shaped limestone in the first member of the Maokou Formation in well DB 1, Da'an exploration area, western Chongqing. A breakthrough has been made in the unconventional gas exploration of argillaceous limestone in the southern Sichuan and western Chongqing area, showing good exploration prospects in this area. The eyelid and eyeball-shaped limestone in the first member of the Maokou Formation in the Sichuan Basin has the characteristics of self-generation and self-storage, continuous and stable distribution and high thermal maturity. The limestone of central gentle slope facies shows no water sensitivity or acid sensitivity, and is dominated by carbonate brittle minerals, which is ideal for acid-fracturing development. It is of great significance to study the characteristics and main controlling factors of the organic rich limestone reservoir. Taking well DB 1 as an example, this paper carried out a study on the petrology, sedimentology and reservoir characteristics of the first member of the Maokou Formation, and it is found that, deposited on the central gentle slope with frequent water activity and abundant organism, the dark gray to black micrite with high organic matter content has good physical properties. In general, submember c has better physical properties than submember a. The development degree of macropores in eyelid-shaped limestone is higher than that in eyeball-shaped limestone, and the development degree of micropores is not much different. The main pore types of the first member of the Maokou Formation include dissolution pores, fractures, clay mineral apertures and organic pores. The pores in clay minerals (mainly talc) and organic matters are mainly distributed in the eyelid-shaped limestone. Depositional process and diagenesis are the main factors controlling the development of the eyelid and eyeball-shaped limestone reservoirs. The central gentle slope facies controls the development and distribution features of the organic-rich micrites. Diagenesis as well as fracture and dissolution effects improve the reservoir capacity of limestone, which is critical for hydrocarbon accumulation. Stable and high yield commercial gas flow was obtained in the vertical wells and horizontal wells in the first member of the Maokou Formation which has high organic matter content in well DB 1 block in the western Chongqing area, indicating that the accumulation and occurrence conditions of limestone source rock gas are good in the first member of the Maokou Formation. It has two kinds of accumulation modes with self-generation and self-storage dominance and short distance aggregation of local structural bands, and has the characteristics of continuous distribution of gas reservoir and large resource scale. The "continuous gas reservoir: in the limestone source rock in the first member of the Maokou Formation has great exploration potential, which will become an important exploration target with good potential in the Sichuan Basin.

Shale lithofacies has an important influence on shale reservoirs. It controls the hydrocarbon generation capacity, storage performance and fracturing performance of shale to a certain extent. In order to study the shale lithofacies characteristics, reservoir characteristics and evaluation of Wufeng-Longmaxi formations in the northeast Zhaotong area, a detailed research was carried out based on core, thin section, X-ray diffraction and various geochemical test data. Calcareous/siliceous mixed shale lithofacies, mixed shale lithofacies, clayey/siliceous mixed shale lithofacies, mixed siliceous shale lithofacies, clay-rich siliceous shale lithofacies are developed in the study area. There is a difference in the vertical distribution of lithofacies between the south and the north of the study area. The lithofacies from Wufeng Formation to the first sub-member of the first member of Longmaxi Formation (Long1-1 submember) presents the characteristics of transition from clayey shale lithofacies associa- tion to siliceous shale lithofacies association and then to mixed shale lithofacies association in the southern area, while the northern area shows a transition trend from mixed shale lithofacies association to siliceous shale lithofacies association and then to mixed shale lithofacies association. Horizontally, the lithofacies distribution is highly heterogeneous and has poor continuity. The reservoir characteristics of different lithofacies are different. Siliceous shale has good reservoir properties, with the characteristics of "high TOC content, high gas content and high brittle mineral content". The TOC content and gas content of clayey shale are high, but the content of brittle minerals is very low. The properties of mixed shale reservoirs are complex, and generally, the mixed shale reservoirs with high siliceous content have better properties. Based on TOC content, gas content and brittle mineral content, the shale lithofacies evaluation standard is established by combining analytic hierarchy process and entropy method, and the dominant lithofacies are determined. Mixed siliceous shale lithofacies, calcium-rich siliceous shale litho- facies, calcareous/siliceous mixed shale lithofaciesis are class Ⅰ dominant lithofacies; clay-rich siliceous shale lithofacies, mixed shale lithofacies and clayey/siliceous mixed shale lithofacies are class Ⅱ dominant lithofacies; mixed clayey shale lithofacies and silicon-rich clayey shale lithofacies are non-dominant lithofacies.

To further study the reservoir characteristics and adsorption capacity of the Taiyuan Formation shale in the South North China Basin (SNCB), the pore structure and adsorption capacity of shale are discussed using various analysis tests, including elemental geochemistry, organic geochemistry, mineral composition, low-temperature nitrogen adsorption (LTNA), and methane adsorption experiments. The results indicate that the Taiyuan Formation shale formed in a poor oxygen and anaerobic sedimentary environment in still water. The average value of total organic carbon (TOC) content is 2.37%. The organic matter type mainly consists of type III kerogen. The vitinite reflectance (Ro) ranges from 3.11% to 3.50%. The clay mineral content varies greatly, averaging at 40.7%, while the quartz content averages at 37.7%. The Taiyuan Formation shale mainly develops interparticle (InterP) pores, followed by organic pores, intraparticle (IntraP) pores, solution pores, and microfractures. BET specific surface area (SSA) is between 9.47 m2/g and 22.14 m2/g, while pore volume (PV) ranges from 0.0098 cm3/g to 0.022 cm3/g, indicating favorable conditions for shale gas storage. According to the results of the CH4 adsorption experiment, Langmuir volume from Taiyuan Formation shales exhibits 1.35~4.30 cm3/g, indicating excellent adsorption capacity. TOC content shows a positive correlation with both Langmuir volume and BET SSA from Taiyuan Formation shales, suggesting that TOC plays a crucial role in controlling microscopic pores and gas adsorption capacity. Organic matter enhances the shale adsorption capacity by providing abundant pore SSA. Due to formation compaction, the pore size of clay minerals decreases, leading to an increase in pore SSA, while kaolinite exhibits weak hydrophilic ability. Consequently, with the increase in clay minerals and kaolinite content, the shale adsorption capacity is enhanced to a certain extent. However, an increase in the carbonate mineral content may result in a decrease in the proportion of clay minerals, therefore reducing the CH4 adsorption capacity of shale.