Marine and Petroleum Geology最新文献

{"title":"Evolution of rimmed carbonate platform architecture controlled by sea-level change: Insights from the Lower-Middle Cambrian of the Northern Tarim Basin, China","authors":"Qing He ,&nbsp;Kaibo Shi ,&nbsp;Yongsheng Ma ,&nbsp;Bo Liu ,&nbsp;Jun Han ,&nbsp;Jun Li ,&nbsp;Xiangyu Bai ,&nbsp;Chun Wu ,&nbsp;Adam D. McArthur ,&nbsp;Nigel P. Mountney","doi":"10.1016/j.marpetgeo.2024.107215","DOIUrl":"10.1016/j.marpetgeo.2024.107215","url":null,"abstract":"<div><div>The sedimentary architecture of carbonate platforms is determined by distinct paleobiological, tectonics, climatic, oceanic and environmental conditions. During the Cambrian period, a rimmed carbonate platform system developed over an area of ∼28 × 10⁴ km² in the Tarim Basin. However, the evolution mechanism and its predominant controlling factors remain poorly understood. The investigation utilized integrated analysis of cores, thin sections, 3-D seismic, well logging and geochemical data to explain the sequence stratigraphic framework, depositional architecture and main controlling factors. Sixteen distinct microfacies (MF1–MF16) are identified based on thin-section analysis of the five lithofacies, which could be further grouped into fourteen microfacies associations (MA1-MA14). These fourteen microfacies associations respectively represent fourteen facies belts of the five facies of the shelf, outer ramp, middle ramp, platform margin and restricted platform. Microfacies and seismic characteristics have provided the basis for establishing a sequence-stratigraphic framework. Two regionally extensive second-order sequences (CS1-CS2) are developed in the Lower-Middle Cambrian succession; CS1 incorporates five third-order sequences (Sq1-Sq5); CS2 incorporates three third-order sequences (Sq6-Sq8). The lateral migration and vertical arrangement of depositional facies resulted in a unique depositional architecture. The overall carbonate platform architecture is interpreted from 3D seismic data, integrated with the depositional facies interpretations to document the evolution of the depositional setting over time from a broad shelf (Sq1-Sq2), to a distally steepening ramp (Sq3-Sq4), to a weekly rimmed platform (Sq5), and finally to a strongly rimmed platform (Sq6-Sq8). Relative sea-level (RSL) curves were reconstructed through an integrated analysis of Fischer plots from three wells. The determined RSL curve matches closely with reconstructed paleo-water depths indicated by the distribution of microfacies types. The inferred paleo-water depths changes comprise two long-term shallow–deep–shallow trends, upon which eight intermediate-term cycles are superimposed. Microfacies also have been applied to explain the evolution of the platform in response to RSL change and other environmental factors. A major transgression occurred in the lower parts of CS1. Results demonstrate that RSL and paleo-water depth changes in the Lower-Middle Cambrian are consistent with known global sea-level changes indicated by geochemical elements. The architectural and sequence-stratigraphic evolution of the progradational rimmed carbonate platform was controlled principally by eustasy. This study is important due to the limited information on Cambrian rimmed platforms.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"171 ","pages":"Article 107215"},"PeriodicalIF":3.7,"publicationDate":"2024-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142703234","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":"Inner architecture of fan delta front deposits: An outcrop example from Xiguayuan formation, Luanping Basin, northeast China","authors":"Zhuo Wen ,&nbsp;Guangqing Yao ,&nbsp;Xiaobo Zhao ,&nbsp;Xiao Lei ,&nbsp;Xinguang Wang ,&nbsp;Haodong Tang ,&nbsp;Xinyang Wu ,&nbsp;Zhongming Huang","doi":"10.1016/j.marpetgeo.2024.107212","DOIUrl":"10.1016/j.marpetgeo.2024.107212","url":null,"abstract":"<div><div>The fan delta front deposit is a notable reservoir type in the basin margin and typically exhibits high heterogeneity in reservoir architecture. With the deepening of exploration and development of oil and gas fields, the study of lower-order depositional architectures is relatively weak, and their implication on remaining oil distribution and enrichment are poorly understood. Field outcrops of the fan delta front deposit exhibit first-hand data of lithofacies, association, and depositional architectures, effectively providing insights for underground reservoir research to guide the development of oil fields, such as high water–cut oil fields in the late development period. Herein, we considered the fan delta front outcrops of the Sangyuan section as an object to reveal the depositional architectures located in the Luanping Basin, northeast China. Using meticulous artificial fieldwork and unmanned aerial vehicle observation, we focused on the 4th-order (single sandbody) and 3rd-order (composite laminaset groups) architectural units. Based on field observations, quantitative statistics, and model matching and guidance, architectural models of the fan delta front in the Sangyuan section were established in response to the high-frequency lake-level. In addition, genetic types of remaining oil controlled by architectural features in Wenchang B oil field during the high water–cut stage were further discussed, and suitable strategies and measures are proposed to produce different types of remaining oil. Results indicate that there are twelve basic types of lithofacies and three types of a single sandbody developed in the Sangyuan section, and evidently, the dimensions and spatial stacking patterns of 4th-order architectural units are closely related to high-frequency lake-level fluctuation, that is, with the rise of lake-level, the thickness and width of a single sandbody gradually decrease, whereas the width–thickness ratio gradually increases. Meanwhile, the spatial stacking patterns of sandbody gradually evolution from the downcut type to the superposition or butted type and finally to the isolated type. A single sandbody is divided into one or more composite laminate groups by the interfaces of 3rd-order architectural elements, which are identified according to the flow regime and sedimentary structures. Different orders of architectural units have different controlling effects over remaining oil distribution and enrichment, and the corresponding technical measures are proposed to enhance the remaining oil recovery. The above mentioned analyses can provide a valuable reference for oil and gas production in the late stage of an oil field with a similar depositional environment.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"172 ","pages":"Article 107212"},"PeriodicalIF":3.7,"publicationDate":"2024-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142722600","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":"Upscaling characterizing pore connectivity, morphology and orientation of shale from nano-scale to micro-scale","authors":"He Zheng ,&nbsp;Feng Yang ,&nbsp;Qiulei Guo ,&nbsp;Kangfei Liu","doi":"10.1016/j.marpetgeo.2024.107213","DOIUrl":"10.1016/j.marpetgeo.2024.107213","url":null,"abstract":"<div><div>The fluid transport in tight rocks are dominantly controlled by the preferential migration pathways. In this paper, the geometric and topological characteristics of multiscale pore systems of shale were delicately characterized by X-ray computed tomography (CT) and focused ion beam-scanning electron microscope (FIB-SEM). The preferential migration pathways of the three-dimensional pore network of shale were recognized at the micro-to nano-scales. According to the constructed pore network model based on the maximum sphere algorithm, the pore geometric parameters such as pore size, pore coordination number, pore throat size and length were calculated using Micro-CT, Nano-CT and FIB-SEM. Besides, sphericity, azimuthal angle and polar angle of pores were counted to characterize pore morphology and pore orientation. Different from the commonly reported results at the macroscopic scale, this paper proposed to use pore orientation to represent the preferential migration orientation at the pore scale. Results show that the general pore size range of shale is 0.054–50 μm, and the dominant pore size ranges observed using Micro-CT, Nano-CT and FIB-SEM are 2.759∼5 μm, 200∼500 nm and 54∼200 nm, respectively. Pore connectivity is best at FIB-SEM observation scale, middle at Nano-CT observation scale and worst at Micro-CT observation scale. The connected pore volume percentage using Micro-CT, Nano-CT and FIB-SEM is 10.2%, 50.8%, and 90.5%, respectively. Pores are divided into blade pores with the sphericity of being &lt;0.5, rod pores with the sphericity of being 0.5–0.8, and spherical pores with the sphericity of being &gt;0.8. Though the spherical pores and rod pores are dominant in number, the blade pores have larger pore volumes, larger pore diameters and better pore connectivity, and are conducive to fluid transportation. The blade pores are corresponding to the slit-shaped pores and microfractures. The statistics of pore polar angle show that the preferred pore orientations are close to the parallel bedding plane, which is the dominant channel directions of fluid migration.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"172 ","pages":"Article 107213"},"PeriodicalIF":3.7,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142722596","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":"Controls of paleogeomorphology on organic matter accumulation as recorded in Ordovician–Silurian marine black shales in the western South China Block","authors":"Feng Liang ,&nbsp;Qun Zhao ,&nbsp;Qin Zhang ,&nbsp;Yuman Wang ,&nbsp;Shangwen Zhou ,&nbsp;Zhen Qiu ,&nbsp;Wen Liu ,&nbsp;Bo Ran ,&nbsp;Tong Sun","doi":"10.1016/j.marpetgeo.2024.107206","DOIUrl":"10.1016/j.marpetgeo.2024.107206","url":null,"abstract":"<div><div>The Ordovician–Silurian transition represents a critical period marked by the formation of marine shale gas horizons within the South China Block. However, the mechanism for organic matter enrichment of Paleozoic marine shales in the western South China Block remain contentious, primarily due to insufficient understanding of paleogeomorphological evolution. In this paper, we describe the sedimentology of the Ordovician-Silurian succession composed of the Wufeng-Longmaxi Formation in the western South China Block and report new paleontological, and geochemical data for this succession to explore the relationship between basin paleogeomorphology and water mass environment. Nine graptolite zones are identified, spanning from the WF1 (Linxiang Formation) through WF2–WF4 (Wufeng Formation) to LM1–LM5 (Longmaxi Formation) in this well. Based on sedimentological and geochemical analyse results, three distinct stages of redox and paleoproductivity conditions in the water mass have been identified: (1) suboxic environments and low paleoproductivity in WF2–WF4; (2) euxinic and stagnant water conditions in LM1–LM3 accompanying with high paleoproductivity; and (3) anoxic water and low paleoproductivity in LM4–LM5. By integrating marine redox fluctuation, paleoproductivity conditions and regional hiatus (LM1-LM3) observed across multiple successions, we interpret thatthe western margin of the South China Block have been significantly affected by a collision between the South China Block and Yanbian terrane. The results of this study indicate that the accumulation of organic matter in the western margin of the South China Block was predominantly controlled by paleogeomorphology being caused by this collision event.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"172 ","pages":"Article 107206"},"PeriodicalIF":3.7,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142722597","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":"The role of the Andaman Nicobar fault (ANF) in shaping Narcondam offshore: Insights from high-resolution reflection seismic data","authors":"H.K. Srivastav ,&nbsp;D. Ghosal ,&nbsp;J. Jacob","doi":"10.1016/j.marpetgeo.2024.107211","DOIUrl":"10.1016/j.marpetgeo.2024.107211","url":null,"abstract":"<div><div>The study investigates the Andaman Nicobar Fault (ANF) and its role in the evolution of a volcano-supported basin adjacent to Narcondam Island, using three high-resolution 2D seismic reflection profiles. Migrated images show a fluid zone, determined through velocity and polarity analyses, with mean 1/Q values ranging from 0.0165 to 0.0096 for Lines 1 to 3. Additionally, polygonal faults are imaged, with varying thicknesses (0.1–0.4 km) of Miocene age, positioned above the fluid saturated zone. The migrated sections further show the branches of the ANF to be conduits for fluid migration and accumulation within the basinal deposits. The study finally highlights a shift in depocenter during the Neogene period, indicating fluctuations in sediment supply from the Irrawaddy River and the evolution of the ANF branch.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"172 ","pages":"Article 107211"},"PeriodicalIF":3.7,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142722567","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":"Combined use of petroleum inclusion analysis, PVT simulation, and basin modeling for reconstruction of deep fluid phase evolution in condensate gas reservoirs","authors":"Wenzhi Lei ,&nbsp;Dongxia Chen ,&nbsp;Ming Cheng ,&nbsp;Chenyang Cai ,&nbsp;Qiaochu Wang","doi":"10.1016/j.marpetgeo.2024.107210","DOIUrl":"10.1016/j.marpetgeo.2024.107210","url":null,"abstract":"<div><div>The reconstruction of the fluid phase evolution in deep condensate gas reservoirs can reveal the mechanism of condensate gas formation, facilitating the early formulation of drilling strategies. However, the complexity of petroleum fluid phase evolution during hydrocarbon generation, migration, and accumulation poses numerous challenges for the reconstruction process. Therefore, petroleum fluid inclusion analysis, PVT phase simulation, and basin modeling were used to achieve the reconstruction of phase states during key geological periods, elucidating the phase evolution of the deep condensate reservoirs in the Dongying Depression during the whole process. The modeled results show that the mature source rocks contributed to the charging and accumulation of liquid oils (38–14 Ma). Next, a low oil cracking conversion rate limited the increase of gaseous hydrocarbon fraction, so the accumulated hydrocarbons remained in a liquid phase (14–0 Ma). The late external gas inputs significantly increased the gas-oil ratio in the reservoirs, leading to the transition from the liquid oil phase to the condensate phase (5–0 Ma). The fluid compositions obtained from hydrocarbon inclusions and the physical properties of present-day condensates can effectively constrain basin modeling, leading to reliable simulation results. This work revealed that the hydrocarbon generation controls the initial hydrocarbon components in the traps for the phase evolution. Furthermore, the secondary alterations including oil cracking and gas inputs influence the proportion of methane of petroleum in the deep reservoirs, which dominates the phase evolution. Deep petroleum fluid phase changes mainly require the molar ratio of the input gas more than 50%. A model was proposed to explain the formation of deep condensate reservoirs. A series of gas inputs and escape in the successive lithological traps controls an orderly phase change of deep petroleum, and the amount of deeper gas determines the range of the existence of condensate gas reservoirs. This study not only guides the exploration of deep condensate in the Dongying Depression but also offers a workflow for the research on the formation and evolution of condensate reservoirs in other global regions.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"171 ","pages":"Article 107210"},"PeriodicalIF":3.7,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142703472","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":"Assessing the geochemical correlation between petroleum source rocks in the Brazilian Equatorial margin basins and global oceanic anoxic events","authors":"Ediane B. da Silva,&nbsp;Helio J.P. Severiano Ribeiro,&nbsp;Eliane Soares de Souza","doi":"10.1016/j.marpetgeo.2024.107205","DOIUrl":"10.1016/j.marpetgeo.2024.107205","url":null,"abstract":"<div><div>This research aims to investigate the correlation between the Cretaceous Oceanic Anoxic Events (OAEs) and the source rocks of the Brazilian Equatorial Margin (BEM) basins. These source rocks, particularly from the Cenomanian-Turonian interval, are known to contain high levels of Total Organic Carbon (TOC) and exhibit significant hydrocarbon potential. The principal focus is on how global anoxic events, such as OAE-1b, OAE-1d, and OAE-2, influenced the depositional environments and organic matter types across the BEM basins, which include Foz do Amazonas, Pará-Maranhão, Barreirinhas, Ceará, and Potiguar. Key results indicate a strong correlation between periods of anoxia and the accumulation of organic-rich sediments in these basins. The Foz do Amazonas Basin features predominantly terrestrial-derived kerogen (Type III), while the Ceará and Potiguar basins show marine-derived kerogen (Type I and II), aligning with global productivity patterns during anoxic events. These variations in kerogen type reflect differences in depositional environments influenced by sea-level changes and nutrient influx. The research concludes that the OAEs significantly impacted organic matter preservation and hydrocarbon generation in the BEM basins. The study's findings contribute to the broader understanding of how Cretaceous OAEs shaped the geochemical and sedimentary processes in equatorial Atlantic margins, highlighting the potential for further oil and gas exploration in these regions.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"172 ","pages":"Article 107205"},"PeriodicalIF":3.7,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142722598","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":"Experimental tests and modeling of CO2 and H2S co-sequestration in saline aquifers","authors":"Krzysztof Labus","doi":"10.1016/j.marpetgeo.2024.107196","DOIUrl":"10.1016/j.marpetgeo.2024.107196","url":null,"abstract":"<div><div>A simulation study and a series of autoclave experiments were performed, reproducing gas-rock-water systems under reservoir conditions, after injection of CO₂ and the mixture of CO₂ with H₂S into rocks representing the Upper Silesian Coal Basin and the adjacent Małopolska Block (Central Europe). The water-rock-gas interactions were modeled in two stages: the first–aimed at simulating the short-term changes in system impacted by the gas injection, and the second–long-term effects of sequestration.</div><div>On the basis of the simulations, the reactions behind mineral transformations were identified. These phenomena are different for the injection of CO₂ alone. and CO₂+H₂S mixtures, resulting in the formation of secondary minerals responsible for mineral sequestration. Depending on the original mineral composition of the rock, in the case of pure CO₂, these are mainly carbonate minerals siderite, dawsonite, magnesite, dolomite and calcite, while in the case of mixture injection: elemental sulfur, sulfur sulfides–pyrite and pyrrhotite.</div><div>In experiments with the H₂S+CO₂ mixture, dissolution of skeletal grains was observed, which was most visible in the case of carbonates, feldspars, and chlorites. The analysis of rocks containing hematite revealed the formation of elemental sulfur surrounded by FeS₂ crystals, which had not been previously reported.</div><div>The experiments generally confirmed the interactions in gas-rock-water systems identified by numerical simulation. This allowed to estimate the amount of mineral phases precipitated or dissolved in the analyzed reactions, and consequently the impact on changes in porosity and the amount of sequestered carbon dioxide and sulfur.</div><div>In samples abundant in carbonate minerals (the Dębowiec Formation psephites), the decomposition of ankerite, due to the injection of CO₂+H₂S, is not compensated for by the precipitation of sufficient amounts of other carbonates, which leads to the desequestration process–CO₂ release.</div><div>Based on the calculations, it was found that the potentially most favorable conditions for the sequestration occur in the Paralic Series mudstones, rich in chlorites–a maximum of 22.36 kg CO₂/m³ and 12.50 kg S/m³, trapping capacity after 10,000 years of storage.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"171 ","pages":"Article 107196"},"PeriodicalIF":3.7,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142656663","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":"On the generation of light hydrocarbons from the closed pores of Jurassic strata, Sichuan Basin","authors":"Fei Liu ,&nbsp;Yuanjia Han ,&nbsp;Hanyong Bao ,&nbsp;Ming Fan ,&nbsp;Zhiguo Shu ,&nbsp;Tian Dong ,&nbsp;Zhiliang He","doi":"10.1016/j.marpetgeo.2024.107208","DOIUrl":"10.1016/j.marpetgeo.2024.107208","url":null,"abstract":"<div><div>Light hydrocarbons (C₁-C₉) offer a specific opportunity to study petroleum generation mechanisms. However, a significant amount of light hydrocarbons evaporate during sample collection, preservation, and preparation. This study aims to identify the origin of light hydrocarbons preserved in the closed pores of Jurassic shale strata from the Sichuan Basin where evaporative losses have been minimized. Twenty-one samples of various maturity levels and lithofacies were investigated using a new approach based on online decrepitation-gas chromatography. Light hydrocarbons were released from the closed pores of finely stratified mudstone, limestone, and siltstone. Among these, gaseous hydrocarbons in the C₁-C₅ range were utilized to discriminate between petroleum generated by two opposing reactions, i.e., free radical and carbenium ion cracking. Accordingly, <em>in situ</em> petroleum can be divided into three types. (1) Free radical cracking type: a predominance of methane and straight-chain alkanes in the gaseous hydrocarbon range; (2) Carbenium ion cracking type: a deficiency of methane and straight-chain alkanes in gaseous hydrocarbons; (3) Mixed cracking type: their gaseous hydrocarbons exhibit intermediate compositions between those of free radical and carbenium ion cracking types. Differences in the chemical composition of the gaseous hydrocarbons, which can be used to discriminate between the two generation mechanisms, were further supported by variations in the mineral composition, e.g., calcite and mixed-layer clay minerals are characteristic of free radical reaction and carbenium ion reaction, respectively. The present classification diagrams for gaseous hydrocarbons are based on the Jurassic shale strata of the Sichuan Basin. This novel approach for determining the whole range of hydrocarbons from closed pores shows promising prospects for deciphering the origin of light hydrocarbons and thus may be extended to other regions of interest.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"171 ","pages":"Article 107208"},"PeriodicalIF":3.7,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142656662","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":"Effects of solvent extraction on pore structure properties and oil distribution in shales of alkaline lacustrine basins","authors":"Cunjian Zhang ,&nbsp;Qinhong Hu ,&nbsp;Qiming Wang ,&nbsp;Shengyu Yang ,&nbsp;Xiuhong Li ,&nbsp;Zhi Yang ,&nbsp;Shuang Yu ,&nbsp;Jianping Yan ,&nbsp;Changan Du","doi":"10.1016/j.marpetgeo.2024.107207","DOIUrl":"10.1016/j.marpetgeo.2024.107207","url":null,"abstract":"<div><div>Shale contains numerous nano-scale pores, whose pore structure property changes affect petroleum flow, complicating shale oil accumulation and exploration. Twelve shale samples from the Permian Fengcheng Formation in the Mahu Sag and the Permian Lucaogou Formation in the Jimusar Sag in northwestern China were analyzed to investigate the coupled oil distribution and pore structure in shales from alkaline lacustrine basins. Shale samples were comprehensively analyzed before and after solvent extraction using X-ray diffraction, total organic carbon measurement, Rock-Eval analyses, field emission-scanning electron microscopy, nitrogen physisorption (NP), and (ultra) small-angle X-ray scattering [(U)SAXS] to assess nanoscale pore structure (2–300 nm in diameter) and oil distribution. Solvent extraction increased total pore volume and specific surface area (SSA). However, the accessibility of nanoscale pores remains limited. Additionally, even after retained oil removal, (U)SAXS-derived total pore volumes are 1–10.4 times larger than NP-derived connected pore volumes. Complex variations in pore volume and SSA mainly result from the removal of extractable organic matter (EOM) and the refilling of small pores by organic matter. Despite the relatively small pore volume of mesopores (2–50 nm), the amount of EOM distribution in mesopores is comparable to that in macropores (50–300 nm); therefore, it is crucial not to overlook the retention capacity of mesopores for EOM. Macropores, particularly interparticle pores associated with quartz and feldspar, play a crucial role in oil mobility. The quantity and composition of EOM, along with other factors, can alter pore structure before and after solvent extraction and should be considered in evaluating the distribution and content of free oil.</div></div>","PeriodicalId":18189,"journal":{"name":"Marine and Petroleum Geology","volume":"171 ","pages":"Article 107207"},"PeriodicalIF":3.7,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142656660","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}