Petroleum Exploration and Development最新文献

{"title":"Phase behavior of CO2-shale oil in nanopores","authors":"Yuhan WANG ,&nbsp;Zhengdong LEI ,&nbsp;Yishan LIU ,&nbsp;Xiuxiu PAN ,&nbsp;Zhewei CHEN ,&nbsp;Yuanqing ZHANG ,&nbsp;Xiaoyu ZHENG ,&nbsp;Pengcheng LIU ,&nbsp;Yi HAN","doi":"10.1016/S1876-3804(25)60013-9","DOIUrl":"10.1016/S1876-3804(25)60013-9","url":null,"abstract":"<div><div>Considering the interactions between fluid molecules and pore walls, variations in critical properties, capillary forces, and the influence of the adsorbed phase, this study investigates the phase behavior of the CO₂-shale oil within nanopores by utilizing a modified Peng-Robinson (PR) equation of state alongside a three-phase (gas-liquid-adsorbed) equilibrium calculation method. The results reveal that nano-confinement effects of the pores lead to a decrease in both critical temperature and critical pressure of fluids as pore size diminishes. Specifically, CO₂ acts to inhibit the reduction of the critical temperature of the system while promoting the decrease in critical pressure. Furthermore, an increase in the mole fraction of CO₂ causes the critical point of the system to shift leftward and reduces the area of the phase envelope. In the shale reservoirs of Block A in Gulong of the Daqing Oilfield, China, pronounced confinement effects are observed. At a pore diameter of 10 nm, reservoir fluids progressively exhibit characteristics typical of condensate gas reservoirs. Notably, the CO₂ content in liquid in 10 nm pores increases by 20.0% compared to that in 100 nm pores, while the CO₂ content in gas decreases by 10.8%. These findings indicate that confinement effects enhance CO₂ mass transfer within nanopores, thereby facilitating CO₂ sequestration and improving microscopic oil recovery.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 1","pages":"Pages 182-195"},"PeriodicalIF":7.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143464168","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"New progress and future exploration targets in petroleum geological research of ultra-deep clastic rocks in Kuqa Depression, Tarim Basin, NW China","authors":"Qinghua WANG ,&nbsp;Haijun YANG ,&nbsp;Wei YANG","doi":"10.1016/S1876-3804(25)60006-1","DOIUrl":"10.1016/S1876-3804(25)60006-1","url":null,"abstract":"<div><div>Significant exploration progress has been made in ultra-deep clastic rocks in the Kuqa Depression, Tarim Basin, over recent years. A new round of comprehensive geological research has formed four new understandings: (1) Establish structural model consisting of multi-detachment composite, multi-stage structural superposition and multi-layer deformation. Multi-stage structural traps are overlapped vertically, and a series of structural traps are discovered in underlying ultra-deep layers. (2) Five sets of high-quality large-scale source rocks of three types of organic phases are developed in the Triassic and Jurassic systems, and forming a good combination of source-reservoir-cap rocks in ultra-deep layers with three sets of large-scale regional reservoir and cap rocks. (3) The formation of large oil and gas fields is controlled by four factors which are source, reservoir, cap rocks and fault. Based on the spatial configuration relationship of these four factors, a new three-dimensional reservoir formation model for ultra-deep clastic rocks in the Kuqa Depression has been established. (4) The next key exploration fields for ultra-deep clastic rocks in the Kuqa Depression include conventional and unconventional oil and gas. The conventional oil and gas fields include the deep multi-layer oil-gas accumulation zone in Kelasu, tight sandstone gas of Jurassic Ahe Formation in the northern structural zone, multi-target layer lithological oil and gas reservoirs in Zhongqiu–Dina structural zone, lithologic-stratigraphic and buried hill composite reservoirs in south slope and other favorable areas. Unconventional oil and gas fields include deep coal rock gas of Jurassic Kezilenuer and Yangxia formations, Triassic Tariqike Formation and Middle-Lower Jurassic and Upper Triassic continental shale gas. The achievements have important reference significance for enriching the theory of ultra-deep clastic rock oil and gas exploration and guiding the future oil and gas exploration deployment.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 1","pages":"Pages 79-94"},"PeriodicalIF":7.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143464692","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Construction and application of favorable target evaluation system for hot dry rock","authors":"Bo XIONG ,&nbsp;Hao XU ,&nbsp;Chaohe FANG ,&nbsp;Shixiang LI ,&nbsp;Shuling TANG ,&nbsp;Shejiao WANG ,&nbsp;Jingjie WU ,&nbsp;Xuejing SONG ,&nbsp;Lu ZHANG ,&nbsp;Jinwei WANG ,&nbsp;Xiangquan WEI ,&nbsp;Fudong XIN ,&nbsp;Boning TANG ,&nbsp;Yin LONG","doi":"10.1016/S1876-3804(25)60019-X","DOIUrl":"10.1016/S1876-3804(25)60019-X","url":null,"abstract":"<div><div>China has abundant resources of hot dry rocks. However, due to the fact that the evaluation methods for favorable areas are mainly qualitative, and the evaluation indicators and standards are inconsistent, which restrict the evaluation efficiency and exploration process of dry hot rocks. This paper is based on the understanding of the geologic features and genesis mechanisms of hot dry rocks in China and abroad. By integrating the main controlling factors of hot dry rock formation, and using index grading and quantification, the fuzzy hierarchical comprehensive method is applied to establish an evaluation system and standards for favorable areas of hot dry rocks. The evaluation system is based on four indicators: heat source, thermal channel, thermal reservoir and cap rock. It includes 11 evaluation parameters, including time of magmatic/volcanic activity, depth of molten mass or magma chamber, distribution of discordogenic faults, burial depth of thermal reservoir, cap rock type and thickness, surface thermal anomaly, heat flow, geothermal gradient, Moho depth, Curie depth, Earthquake magnitude and focal depth. Each parameter is divided into 3 levels. Applying this evaluation system to assess hot dry rock in central Inner Mongolia revealed that Class I favorable zones cover approximately 494 km², while Class II favorable zones span about 5.7×10⁴ km². The Jirgalangtu Sag and Honghaershute Sag in the Erlian Basin, along with Reshuitang Town in Keshiketeng Banner, Reshui Town in Ningcheng County, and Reshuitang Town in Aohan Banner of Chifeng City, are identified as Class I favorable zones for hot dry rock resources. These areas are characterized by high-temperature subsurface molten bodies or magma chambers serving as high-quality heat sources, shallow thermal reservoir depths, and overlying thick sedimentary rock layers acting as caprock. The establishment and application of the evaluation system for favorable areas of hot dry rock are expected to provide new approaches and scientific basis for guiding the practice of selecting hot dry rock areas in China.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 1","pages":"Pages 258-271"},"PeriodicalIF":7.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143464792","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Oil production characteristics and CO2 storage mechanisms of CO2 flooding in ultra-low permeability sandstone oil reservoirs","authors":"Xiliang LIU ,&nbsp;Hao CHEN ,&nbsp;Yang LI ,&nbsp;Yangwen ZHU ,&nbsp;Haiying LIAO ,&nbsp;Qingmin ZHAO ,&nbsp;Xianmin ZHOU ,&nbsp;Hongbo ZENG","doi":"10.1016/S1876-3804(25)60014-0","DOIUrl":"10.1016/S1876-3804(25)60014-0","url":null,"abstract":"<div><div>Using the ultra-low permeability reservoirs in the L block of the Jiangsu oilfield as an example, a series of experiments, including slim tube displacement experiments of CO₂-oil system, injection capacity experiments, and high-temperature, high-pressure online nuclear magnetic resonance (NMR) displacement experiments, are conducted to reveal the oil/gas mass transfer pattern and oil production mechanisms during CO₂ flooding in ultra-low permeability reservoirs. The impacts of CO₂ storage pore range and miscibility on oil production and CO₂ storage characteristics during CO₂ flooding are clarified. The CO₂ flooding process is divided into three stages: oil displacement stage by CO₂, CO₂ breakthrough stage, CO₂ extraction stage. Crude oil expansion and viscosity reduction are the main mechanisms for improving recovery in the CO₂ displacement stage. After CO₂ breakthrough, the extraction of light components from the crude oil further enhances oil recovery. During CO₂ flooding, the contribution of crude oil in large pores to the enhanced recovery exceeds 46%, while crude oil in medium pores serves as a reserve for incremental recovery. After CO₂ breakthrough, a small portion of the crude oil is extracted and carried into nano-scale pores by CO₂, becoming residual oil that is hard to recover. As the miscibility increases, the CO₂ front moves more stably and sweeps a larger area, leading to increased CO₂ storage range and volume. The CO₂ full-storage stage contributes the most to the overall CO₂ storage volume. In the CO₂ escape stage, the storage mechanism involves partial in-situ storage of crude oil within the initial pore range and the CO₂ carrying crude oil into smaller pores to increase the volume of stored CO₂. In the CO₂ leakage stage, as crude oil is produced, a significant amount of CO₂ leaks out, causing a sharp decline in the storage efficiency.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 1","pages":"Pages 196-207"},"PeriodicalIF":7.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143464170","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Characteristics of hydraulic fracture network in the tight conglomerate reservoir based on a hydraulic fracturing test site","authors":"Jianhua QIN ,&nbsp;Chenggang XIAN ,&nbsp;Jing ZHANG ,&nbsp;Tianbo LIANG ,&nbsp;Wenzhong WANG ,&nbsp;Siyuan LI ,&nbsp;Jinning ZHANG ,&nbsp;Yang ZHANG ,&nbsp;Fujian ZHOU","doi":"10.1016/S1876-3804(25)60018-8","DOIUrl":"10.1016/S1876-3804(25)60018-8","url":null,"abstract":"<div><div>In order to identify the development characteristics of fracture network in tight conglomerate reservoir of Mahu after hydraulic fracturing, a hydraulic fracturing test site was set up in the second and third members of Triassic Baikouquan Formation (T₁b₂ and T₁b₃) in Ma-131 well area, which learned from the successful experience of hydraulic fracturing test sites in North America (HFTS-1). Twelve horizontal wells and a high-angle coring well MaJ02 were drilled. The orientation, connection, propagation law and major controlling factors of hydraulic fractures were analyzed by comparing results of CT scans, imaging logs, direct observation of cores from Well MaJ02, and combined with tracer monitoring data. Results indicate that: (1) Two types of fractures have developed by hydraulic fracturing, i.e. tensile fractures and shear fractures. Tensile fractures are approximately parallel to the direction of the maximum horizontal principal stress, and propagate less than 50 m from perforation clusters. Shear fractures are distributed among tensile fractures and mainly in the strike-slip mode due to the induced stress field among tensile fractures, and some of them are in conjugated pairs. Overall, tensile fractures alternate with shear fractures, with shear fractures dominated and activated after tensile ones. (2) Tracer monitoring results indicate that communication between wells was prevalent in the early stage of production, and the static pressure in the fracture gradually decreased and the connectivity between wells reduced as production progressed. (3) Density of hydraulic fractures is mainly affected by the lithology and fracturing parameters, which is smaller in the mudstone than the conglomerate. Larger fracturing scale and smaller cluster spacing lead to a higher fracture density, which are important directions to improve the well productivity.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 1","pages":"Pages 245-257"},"PeriodicalIF":7.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143464788","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experiments on the characteristics of upgrading and viscosity reduction of heavy oil under supercritical water conditions","authors":"Zhongwei HUANG,&nbsp;Yazhou SHEN,&nbsp;Xiaoguang WU,&nbsp;Gensheng LI,&nbsp;Tengda LONG,&nbsp;Wenchao ZOU,&nbsp;Weizhen SUN,&nbsp;Haoyang SHEN","doi":"10.1016/S1876-3804(25)60012-7","DOIUrl":"10.1016/S1876-3804(25)60012-7","url":null,"abstract":"<div><div>This paper investigates the macroscopic and microscopic characteristics of viscosity reduction and quality improvement of heavy oil in a supercritical water environment through laboratory experiments and testing. The effect of three reaction parameters, i.e. reaction temperature, reaction time and oil-water ratio, is analyzed on the product and their correlation with viscosity. The results show that the flow state of heavy oil is significantly improved with a viscosity reduction of 99.4% in average after the reaction in the supercritical water. Excessively high reaction temperature leads to a higher content of resins and asphaltenes, with significantly increasing production of coke. The optimal temperature ranges in 380–420 °C. Prolonged reaction time could continuously increase the yield of light oil, but it will also results in the growth of resins and asphaltenes, with the optimal reaction time of 150 min. Reducing the oil-water ratio helps improve the diffusion environment within the reaction system and reduce the content of resins and asphaltenes, but it will increase the cost of heavy oil treatment. An oil-water ratio of 1︰2 is considered as optimum to balance the quality improvement, viscosity reduction and reaction economics. The correlation of the three reaction parameters relative to the oil sample viscosity is ranked as temperature, time and oil-water ratio. Among the four fractions of heavy oil, the viscosity is dominated by asphaltene content, followed by aromatic content and less affected by resins and saturates contents.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 1","pages":"Pages 170-181"},"PeriodicalIF":7.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143464784","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Role of preservation conditions on enrichment and fluidity maintenance of medium to high maturity lacustrine shale oil","authors":"Wenzhi ZHAO ,&nbsp;Wei LIU ,&nbsp;Congsheng BIAN ,&nbsp;Xianyang LIU ,&nbsp;Xiugang PU ,&nbsp;Jiamin LU ,&nbsp;Yongxin LI ,&nbsp;Junhui LI ,&nbsp;Shiju LIU ,&nbsp;Ming GUAN ,&nbsp;Xiuli FU ,&nbsp;Jin DONG","doi":"10.1016/S1876-3804(25)60001-2","DOIUrl":"10.1016/S1876-3804(25)60001-2","url":null,"abstract":"<div><div>In addition to the organic matter type, abundance, thermal maturity, and shale reservoir space, the preservation conditions of source rocks play a key factor in affecting the quantity and quality of retained hydrocarbons in source rocks of lacustrine shale, yet this aspect has received little attention. This paper, based on the case analysis, explores how preservation conditions influence the enrichment of mobile hydrocarbons in shale oil. Research showns that good preservation conditions play three key roles. (1) Ensure the retention of sufficient light hydrocarbons (C₁–C₁₃), medium hydrocarbons (C₁₄–C₂₅) and small molecular aromatics (including 1–2 benzene rings) in the formation, which enhances the fluidity and flow of shale oil; (2) Maintain a high energy field (abnormally high pressure), thus facilitating the maximum outflow of shale oil; (3) Ensure that the retained hydrocarbons have the miscible flow condition of multi-component hydrocarbons (light hydrocarbons, medium hydrocarbons, heavy hydrocarbons, and heteroatomic compounds), so that the heavy hydrocarbons (ΣC₂₅₊) and heavy components (non-hydrocarbons and asphaltenes) have improved fluidity and maximum flow capacity. In conclusion, in addition to the advantages of organic matter type, abundance, thermal maturity, and reservoir space, good preservation conditions of shale layers are essential for the formation of economically viable shale oil reservoirs, which should be incorporated into the evaluation criteria of shale oil-rich areas/segments and considered a necessary factor when selecting favorable exploration targets.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 1","pages":"Pages 1-16"},"PeriodicalIF":7.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143464785","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An intelligent separated zone oil production technology based on electromagnetic coupling principle","authors":"Qinghai YANG ,&nbsp;Chenglong LIAO ,&nbsp;Deli JIA ,&nbsp;Yingjun ZHU ,&nbsp;Chuan YU ,&nbsp;Lingwei KONG ,&nbsp;Yang YU ,&nbsp;Kai DU","doi":"10.1016/S1876-3804(25)60017-6","DOIUrl":"10.1016/S1876-3804(25)60017-6","url":null,"abstract":"<div><div>To address the challenges associated with existing separated zone oil production technologies, such as incompatibility with pump inspection operations, short effective working life, and poor communication reliability, an innovative electromagnetic coupling intelligent zonal oil production technology has been proposed. The core and accessory tools have been developed and applied in field tests. This technology employs a pipe string structure incorporation a release sub, which separates the production and allocation pipe strings. When the two strings are docked downhole, electromagnetic coupling enables close-range wireless transmission of electrical power and signals between the strings, powering multiple downhole intelligent production allocators (IPAs) and enabling two-way communication. Core tools adapted to the complex working conditions downhole were developed, including downhole electricity &amp; signal transmission equipment based on electromagnetic coupling (EST), IPAs, and ground communication controllers (GCCs). Accessory tools, including large-diameter release sub anchor and cable-crossing packers, have also been technically finalized. Field tests conducted on ten wells in Daqing Oilfield demonstrated that the downhole docking of the two strings was convenient and reliable, and the EST worked stably. Real-time monitoring of flow rate, pressure and temperature in separate layers and regulation of zonal fluid production were also achieved. This technology has enhanced reservoir understanding and achieved practical production results of increased oil output with reduced water cut.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 1","pages":"Pages 230-244"},"PeriodicalIF":7.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143464169","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Origin and distribution model of thin dolomite reservoirs in the lower sub-member of Mao 2 Member of Middle Permian Maokou Formation in Wusheng-Tongnan area, Sichuan Basin, SW China","authors":"Xiucheng TAN ,&nbsp;Ruyi HE ,&nbsp;Wenjie YANG ,&nbsp;Bing LUO ,&nbsp;Jiangbo SHI ,&nbsp;Lianjin ZHANG ,&nbsp;Minglong LI ,&nbsp;Yuxin TANG ,&nbsp;Di XIAO ,&nbsp;Zhanfeng QIAO","doi":"10.1016/S1876-3804(25)60009-7","DOIUrl":"10.1016/S1876-3804(25)60009-7","url":null,"abstract":"<div><div>This paper discusses the characteristics and formation mechanism of thin dolomite reservoirs in the lower submember of the second member of the Permian Maokou Formation (lower Mao 2 Member) in the Wusheng—Tongnan area of the Sichuan Basin, SW China, through comprehensive analysis of geological, geophysical and geochemical data. The reservoir rocks of the lower Mao 2 Member are dominated by porphyritic vuggy dolomite and calcareous dolomite or dolomitic limestone, which have typical karst characteristics of early diagenetic stage. The dolomites at the edge of the karst system and in the fillings have dissolved estuaries, and the dolomite breccia has micrite envelope and rim cement at the edge, indicating that dolomitization is earlier than the early diagenetic karstification. The shoal facies laminated dolomite is primarily formed by the seepage reflux dolomitization of moderate-salinity seawater. The key factors of reservoir formation are the bioclastic shoal deposition superimposed with seepgae reflux dolomitization and the karstification of early diagenetic stage, which are locally reformed by fractures and hydrothermal processes. The development of dolomite vuggy reservoir is closely related to the upward-shallowing sequence, and mainly occurs in the late highstand of the fourth-order cycle. Moreover, the size of dolomite is closely related to formation thickness, and it is concentrated in the formation thickness conversion area, followed by the thinner area. According to the understanding of insufficient accommodation space in the geomorphic highland and the migration of granular shoal to geomorphic lowland in the late highstand of the third-order cycle, it is proposed that the large-scale shoal-controlled dolomite reservoirs are distributed along structural highs and slopes, and the reservoir-forming model with shoal, dolomitization and karstification jointly controlled by the microgeomorphy and sea-level fluctuation in the sedimentary period is established. On this basis, the paleogeomorphology in the lower Mao 2 Member is restored using well-seismic data, and the reservoir distribution is predicted. The prediction results have been verified by the latest results of exploration wells and tests, which provide an important reference for the prediction of thin dolomite reservoirs under similar geological setting.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 1","pages":"Pages 125-142"},"PeriodicalIF":7.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143464627","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mechanisms of fine-grained sedimentation and reservoir characteristics of shale oil in continental freshwater lacustrine basin: A case study from Chang 73 sub-member of Triassic Yanchang Formation in southwestern Ordos Basin, NW China","authors":"Xianyang LIU ,&nbsp;Jiangyan LIU ,&nbsp;Xiujuan WANG ,&nbsp;Qiheng GUO ,&nbsp;Lv Qiqi ,&nbsp;Zhi YANG ,&nbsp;Yan ZHANG ,&nbsp;Zhongyi ZHANG ,&nbsp;Wenxuan ZHANG","doi":"10.1016/S1876-3804(25)60007-3","DOIUrl":"10.1016/S1876-3804(25)60007-3","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Based on recent advancements in shale oil exploration within the Ordos Basin, this study presents a comprehensive investigation of the paleoenvironment, lithofacies assemblages and distribution, depositional mechanisms, and reservoir characteristics of shale oil of fine-grained sediment deposition in continental freshwater lacustrine basins, with a focus on the Chang 7&lt;sub&gt;3&lt;/sub&gt; sub-member of Triassic Yanchang Formation. The research integrates a variety of exploration data, including field outcrops, drilling, logging, core samples, geochemical analyses, and flume simulation. The study indicates that: (1) The paleoenvironment of the Chang 7&lt;sub&gt;3&lt;/sub&gt; deposition is characterized by a warm and humid climate, frequent monsoon events, and a large water depth of freshwater lacustrine basin. The paleogeomorphology exhibits an asymmetrical pattern, with steep slopes in the southwest and gentle slopes in the northeast, which can be subdivided into microgeomorphological units, including depressions and ridges in lakebed, as well as ancient channels. (2) The Chang 7&lt;sub&gt;3&lt;/sub&gt; sub-member is characterized by a diverse array of fine-grained sediments, including very fine sandstone, siltstone, mudstone and tuff. These sediments are primarily distributed in thin interbedded and laminated arrangements vertically. The overall grain size of the sandstone predominantly falls below 62.5 μm, with individual layer thicknesses of 0.05–0.64 m. The deposits contain intact plant fragments and display various sedimentary structure, such as wavy bedding, inverse-to-normal grading sequence, and climbing ripple bedding, which indicating a depositional origin associated with density flows. (3) Flume simulation experiments have successfully replicated the transport processes and sedimentary characteristics associated with density flows. The initial phase is characterized by a density-velocity differential, resulting in a thicker, coarser sediment layer at the flow front, while the upper layers are thinner and finer in grain size. During the mid-phase, sliding water effects cause the fluid front to rise and facilitate rapid forward transport. This process generates multiple “new fronts”, enabling the long-distance transport of fine-grained sandstones, such as siltstone and argillaceous siltstone, into the center of the lake basin. (4) A sedimentary model primarily controlled by hyperpynal flows was established for the southwestern part of the basin, highlighting that the frequent occurrence of flood events and the steep slope topography in this area are primary controlling factors for the development of hyperpynal flows. (5) Sandstone and mudstone in the Chang 7&lt;sub&gt;3&lt;/sub&gt; sub-member exhibit micro- and nano-scale pore-throat systems, shale oil is present in various lithologies, while the content of movable oil varies considerably, with sandstone exhibiting the highest content of movable oil. (6) The fine-grained sediment complexes formed by multiple episodes of ","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 1","pages":"Pages 95-111"},"PeriodicalIF":7.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143464693","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}