Petroleum Exploration and Development最新文献

{"title":"Microscopic mechanisms of intrasource micro-migration and enrichment of lacustrine shale oil: A case study of Chang73 submember of Triassic Yanchang Formation, Ordos Basin, NW China","authors":"Yingzhu WANG ,&nbsp;Yuting HOU ,&nbsp;Jijin YANG","doi":"10.1016/S1876-3804(25)60639-2","DOIUrl":"10.1016/S1876-3804(25)60639-2","url":null,"abstract":"<div><div>To clarify the mechanism of differential enrichment of intrasource shale oil, taking the third of seventh member of the Triassic Yanchang Formation (Chang7₃ submember for short) in the Ordos Basin, NW China as an example, we integrated high-resolution scanning electron microscopy (SEM), optical microscopy, laser Raman spectroscopy, rock pyrolysis, and organic solvent extraction experiments to identify solid bitumen of varying origins, obtain direct evidence of intrasource micro-migration of shale oil, and establish the coupling between the shale nano/micro-fabric and the oil generation, migration and accumulation. The Chang7₃ shale with rich alginite in laminae has the highest hydrocarbon generation potential but a low thermal transformation ratio. Frequent alternations of micron-scale argillaceous-felsic laminae enhance the hydrocarbon expulsion efficiency, yielding consistent aromaticity between in-situ and migrated solid bitumen. Mudstone laminae rich in terrestrial organic matter (OM) and clay minerals exhibit lower hydrocarbon generation threshold but stronger hydrocarbon retention capacity, with a certain amount of light oil/bitumen preserved to differentiate the chemical structure of in-situ versus migrated bitumen. Tuffaceous and sandy laminae contain abundant felsic minerals and migrated bitumen. Tuffaceous laminae develop high-angle microfractures under shale overpressure, facilitating oil charging into rigid mineral intergranular pores of sandy laminae. Fractionation during micro-migration progressively decreases the aromatization of solid bitumen from shale, through tuffaceous and mudstone, to sandy laminae, while increasing light hydrocarbon components and enhancing OM-hosted pore development. The intrasource micro-migration and enrichment of the Chang7₃ shale oil result from synergistic organic-inorganic diagenesis, with crude oil component fractionation being a key mechanism for forming sweet spots in laminated shale oil reservoirs.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 5","pages":"Pages 1247-1261"},"PeriodicalIF":8.0,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145398648","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Research progress and key research directions of shale oil in lacustrine rift basins","authors":"Xusheng GUO ,&nbsp;Baojian SHEN ,&nbsp;Maowen LI ,&nbsp;Huimin LIU ,&nbsp;Zhiming LI ,&nbsp;Shicheng ZHANG ,&nbsp;Yong YANG ,&nbsp;Jingyi GUO ,&nbsp;Yali LIU ,&nbsp;Peng LI ,&nbsp;Xiaoxiao MA ,&nbsp;Mengyun ZHAO ,&nbsp;Pei LI ,&nbsp;Chenjia ZHANG ,&nbsp;Zihan WANG","doi":"10.1016/S1876-3804(25)60629-X","DOIUrl":"10.1016/S1876-3804(25)60629-X","url":null,"abstract":"<div><div>Lacustrine rift basins in China are characterized by pronounced structural segmentation, strong sedimentary heterogeneity, extensive fault-fracture development, and significant variability in thermal maturity and mobility of shale oil. This study reviews the current status of exploration and development of shale oil in such basins and examines theoretical frameworks such as “binary enrichment” and source–reservoir configuration, with a focus on five key subjects: (1) sedimentation-diagenesis coupling mechanisms of fine-grained shale reservoir formation; (2) dynamic diagenetic evolution and hydrocarbon occurrence mechanisms of organic-rich shale; (3) dominant controls and evaluation methods for shale oil enrichment; (4) fracturing mechanisms of organic-rich shale and simulation of artificial fracture networks; and (5) flow mechanisms and effective development strategies for shale oil. Integrated analysis suggests that two major scientific challenges must be addressed: the coupled evolution of fine-grained sedimentation, differential diagenesis, and hydrocarbon generation under tectonic influence and its control on shale oil occurrence and enrichment; and multi-scale, multiphase flow mechanisms and three-dimensional development strategies for lacustrine shale oil in complex fault blocks. In response to current exploration and development bottlenecks, future research will be conducted primarily to: (1) deeply understand organic-inorganic interactions and reservoir formation mechanisms in organic-rich shales, and clarify the influence of high-frequency sequence evolution and diagenetic fluids on reservoir space; (2) elucidate the dynamic processes of hydrocarbon generation, expulsion, and retention across different lithofacies, and quantify their relationship with thermal maturity, including the conditions for the formation of self-sealing systems; (3) develop a geologically adaptive, data- and intelligence-driven shale oil classification and grading evaluation system of shale oil; (4) reveal artificial fracture propagation pattern and optimize physical field coupled fracturing technologies for complex lithofacies assemblages; and (5) overcome challenges in multi-scale geological modeling and multiphase flow characterization, and establish advanced numerical simulation methodologies.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 5","pages":"Pages 1113-1127"},"PeriodicalIF":8.0,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145398657","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Orderly distribution and differential enrichment of conventional and unconventional hydrocarbons in the Cretaceous Qingshankou Formation, northern Songliao Basin, NE China","authors":"Xuefeng BAI ,&nbsp;Junhui LI ,&nbsp;Qiang ZHENG ,&nbsp;Fangju CHEN","doi":"10.1016/S1876-3804(25)60631-8","DOIUrl":"10.1016/S1876-3804(25)60631-8","url":null,"abstract":"<div><div>Based on the petroleum exploration in the Cretaceous Qingshankou Formation, northern Songliao Basin, NE China, integrated with seismic, drilling and logging data, this study investigates the characteristics and genetic mechanisms of orderly distribution and the differential enrichment patterns of conventional and unconventional hydrocarbons in the formation. Key findings involve five aspects. First, the conventional and unconventional hydrocarbons coexist orderly. Laterally, conventional oil, tight oil, and shale oil form a pattern of orderly accumulation from basin margins to the center. Vertically, shale oil, tight oil, and conventional oil develop progressively upward. Second, the coupled tectonic-sedimentary processes govern sedimentary facies differentiation and diagenesis, influencing reservoir physical properties and lithology, thereby controlling the orderly distribution of conventional and unconventional hydrocarbons in space. Third, the coupling of source rock hydrocarbon generation evolution, fault sealing capacity, and reservoir densification determines the orderly coexistence pattern of conventional and unconventional hydrocarbons. Fourth, sequential variations in reservoir physical properties generate distinct dynamic fields that regulate hydrocarbon orderly accumulation. Fifth, enrichment controls are different depending on hydrocarbon types: buoyancy-driven, fault-transport, sandbody-connected, and trap-concentrated, for above-source conventional oil; overpressure-driven, fault-transport, multi-stacked sandbodies, and quasi-continuous distribution for near-source tight oil and gas; self-sourced reservoirs, retention through self-sealing, in-situ accumulation or micro-migration driven by hydrocarbon-generation overpressure for inner-source shale oil. From exploration practices, these findings will effectively guide the integrated deployment and three-dimensional exploration of conventional and unconventional hydrocarbon resources in the Qingshankou Formation, northern Songliao Basin.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 5","pages":"Pages 1140-1149"},"PeriodicalIF":8.0,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145398659","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"New high-efficiency system for improving oil recovery based on the superwetting phenomenon","authors":"Zhaohui ZHOU ,&nbsp;Xiaojie ZHANG ,&nbsp;Qun ZHANG ,&nbsp;Ninghong JIA ,&nbsp;Lu HAN ,&nbsp;Lei ZHANG ,&nbsp;Lu ZHANG ,&nbsp;Weifeng LYU","doi":"10.1016/S1876-3804(25)60643-4","DOIUrl":"10.1016/S1876-3804(25)60643-4","url":null,"abstract":"<div><div>Given that a large amount of crude oil remains on the surface of rocks and is difficult to produce after conventional waterflooding, a new superwetting oil displacement system incorporating the synergy between a hydroxyl anion compound (1OH-1C) and an extended surfactant (S-C₁₃PO₁₃S) was designed. The interfacial tension, contact angle and emulsification performance of the system were measured. The oil displacement effects and improved oil recovery (IOR) mechanisms of 1OH-1C, S-C₁₃PO₁₃S and their compound system were investigated by microscopic visualization oil displacement experiments and core displacement experiments. The results show that 1OH-1C creates a superwetting interface and electrostatic separation pressure on the solid surface, which destroys the strong interactions between crude oil and quartz to peel off the oil film. S-C₁₃PO₁₃S has low interfacial tension, which can promote the flow of remaining oil and emulsify it into oil-in-water emulsions. The compound system of 1OH-1C and S-C₁₃PO₁₃S has both superwettability and low IFT, which can effectively improve oil recovery through a synergistic effect. The oil displacement experiment of low-permeability natural core shows that the compound solution can increase the oil recovery by 16.4 percentage points after waterflooding. This new high-efficiency system is promising for greatly improving oil recovery in low-permeability reservoirs.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 5","pages":"Pages 1301-1313"},"PeriodicalIF":8.0,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145398566","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Technological progress and scientific significance of the drilling of the ten-thousand-meter ultra-deep well TK1, Tarim Basin, NW China","authors":"Haijun YANG ,&nbsp;Chunsheng WANG ,&nbsp;Xianzhang YANG ,&nbsp;Zhi ZHANG ,&nbsp;Xuguang GUO ,&nbsp;Chonghao SUN ,&nbsp;Xiaogang LYU ,&nbsp;Jinlong LIU","doi":"10.1016/S1876-3804(25)60645-8","DOIUrl":"10.1016/S1876-3804(25)60645-8","url":null,"abstract":"<div><div>In 2023, the China National Petroleum Corporation (CNPC) has successfully drilled a 10 000-m ultra-deep well – TK-1 in the Tarim Basin, NW China. This pioneering project has achieved dual breakthroughs in ten-thousand-meter ultra-deep earth science research and hydrocarbon exploration while driving technological advancements in ultra-deep well drilling engineering. The successful completion of TK-1 has yielded transformative geological discoveries. For the first time in exploration history, comprehensive data including cores, well logs, fluids, temperature and pressure were obtained from 10 000-meter depths. These findings conclusively demonstrate the existence of effective source rocks, carbonate reservoirs, and producible conventional hydrocarbons at such extreme depths – fundamentally challenging established petroleum geology paradigms. The results not only confirm the enormous hydrocarbon potential of ultra-deep formations in the Tarim Basin but also identify the most promising exploration targets. From an engineering perspective, the project has established four groundbreaking technological systems: safe drilling in complex pressure systems of ultra-deep wells, optimized and fast drilling in complex and difficult-to-drill formations of ultra-deep wells, wellbore quality control under harsh conditions in ultra-deep wells, and data acquisition in ultra-deep, ultra-high-temperature complex formations. Additionally, ten key tools for ultra-deep well drilling and completion engineering were developed, enabling the successful completion of Asia’s first and the world’s second-deepest vertical well. This achievement has significantly advanced the understanding of geological conditions at depths exceeding 10 000 m and positioned China as one of the few countries with core technologies for ultra-deep well drilling.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 5","pages":"Pages 1329-1339"},"PeriodicalIF":8.0,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145398568","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Whole petroleum system and main controlling factors of hydrocarbon accumulation in the Mesozoic of Ordos Basin, NW China","authors":"Xiuqin DENG ,&nbsp;Bin BAI","doi":"10.1016/S1876-3804(25)60632-X","DOIUrl":"10.1016/S1876-3804(25)60632-X","url":null,"abstract":"<div><div>Based on the investigation of sedimentary filling characteristics and pool-forming factors of the Mesozoic in the Ordos Basin, the whole petroleum system in the Mesozoic is divided, the migration &amp; accumulation characteristics and main controlling factors of conventional–unconventional hydrocarbons are analyzed, and the whole petroleum system model is established. First, the whole petroleum system developed in the Mesozoic takes the high-quality source rocks of the 7^th member of the Triassic Yanchang Formation as the core and mainly consists of low-permeability and unconventional oil and gas reservoirs. It can be divided into four hydrocarbon accumulation domains, including intra-source retained hydrocarbon accumulation domain, near-source tight hydrocarbon accumulation domain, far-source conventional hydrocarbon accumulation domain and transitional hydrocarbon accumulation domain, which together form a continuous, symbiotic, and orderly accumulation entity wherein unconventional resources significantly outweigh conventional ones in proportion. Second, the spatial core area of sedimentary filling is the oil-rich core of the whole petroleum system. From the core to the periphery, the reservoir type evolves as shale oil → tight oil → conventional oil, the accumulation power is dominated by overpressure → buoyancy or overpressure and capillary force, the accumulation scale changes from extensive hundreds of millions of tons to a isolated hundreds of thousands-million of tons, and the gas-oil ratio and methane content decrease. Third, the sedimentary filling system provides the material basis and spatial framework for the whole petroleum system, the superimposed sand body, fault and unconformity constitute the dominant migration pathway of hydrocarbons in the far-source conventional hydrocarbon accumulation domain and the transitional hydrocarbon accumulation domain, the high-quality source rocks provide a solid resource basis for shale oil, and the micro-nano pore throat-fracture network constitute unconventional accumulation space. The hydrocarbon migration and accumulation process is mainly controlled by intense expulsion of hydrocarbon under overpressure in the pool-forming stage and the in-situ re-enrichment controlled by underpressure in post-pool-forming stage. The oil-gas enrichment and long-term preservation depends on the coordination among three factors (stable geological structure, multi-cycle sedimentation, and dual self-sealing). Fourth, the whole petroleum system model is defined as four domains, overpressure + underpressure drive, and dual self-sealing.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 5","pages":"Pages 1150-1163"},"PeriodicalIF":8.0,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145398660","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Structural physical simulation experiment on vertical growth process of strike-slip faults in ultra-deep strata of Tarim Basin, NW China","authors":"Yuan NENG ,&nbsp;Zhou XIE ,&nbsp;Longfei SHAO ,&nbsp;Qiqi RUAN ,&nbsp;Pengfei KANG ,&nbsp;Jianan ZHANG ,&nbsp;Zhiwen TIAN ,&nbsp;Genji LIU","doi":"10.1016/S1876-3804(25)60634-3","DOIUrl":"10.1016/S1876-3804(25)60634-3","url":null,"abstract":"<div><div>In the ultra-deep strata of the Tarim Basin, the vertical growth process of strike-slip faults remains unclear, and the vertical distribution of fractured-cavity carbonate reservoirs is complex. This paper investigates the vertical growth process of strike-slip faults through field outcrop observations in the Keping area, interpretation of seismic data from the Fuman Oilfield, Tarim Basim, NW China, and structural physical simulation experiments. The results are obtained mainly in four aspects. First, field outcrops and ultra-deep seismic profiles indicate a three-layer structure within the strike-slip fault, consisting of fault core, fracture zone and primary rock. The fault core can be classified into three parts vertically: fracture-cavity unit, fault clay and breccia zone. The distribution of fracture-cavity units demonstrates a distinct pattern of vertical stratification, owing to the structural characteristics and growth process of the slip-strike fault. Second, the ultra-deep seismic profiles show multiple fracture-cavity units in the strike-slip fault zone. These units can be classified into four types: top fractured, middle connected, deep terminated, and intra-layer fractured. Third, structural physical simulation experiments and ultra-deep seismic data interpretation reveal that the strike-slip faults have evolved vertically in three stages: segmental rupture, vertical growth, and connection and extension. The particle image velocimetry detection demonstrates that the initial fracture of the fault zone occurred at the top or bottom and then evolved into cavities gradually along with the fault growth, accompanied by the emergence of new fractures in the middle part of the strata, which subsequently connected with the deep and shallow cavities to form a complete fault zone. Fourth, the ultra-deep carbonate strata primarily develop three types of fractured-cavity reservoirs: flower-shaped fracture, large and deep fault and staggered overlap. The first two types are larger in size with better reservoir conditions, suggesting a significant exploration potential.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 5","pages":"Pages 1179-1192"},"PeriodicalIF":8.0,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145398662","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Progradational sequence stratigraphic architecture of the Triassic Yanchang Formation and a case study of Qingcheng Oilfield, Ordos Basin, NW China","authors":"Xiao HUI ,&nbsp;Yunchao HOU ,&nbsp;Tong QU ,&nbsp;Jie ZHANG ,&nbsp;Zhi YANG","doi":"10.1016/S1876-3804(25)60633-1","DOIUrl":"10.1016/S1876-3804(25)60633-1","url":null,"abstract":"<div><div>To address the discrepancies between well and seismic data in stratigraphic correlation of the Triassic Yanchang Formation in the Ordos Basin, NW China, traditional stratigraphic classification schemes, the latest 3D seismic and drilling data, and reservoir sections are thoroughly investigated. Guided by the theory of sequence stratigraphy, the progradational sequence stratigraphic framework of the Yanchang Formation is systematically constructed to elucidate new deposition mechanisms in the depressed lacustrine basin, and it has been successfully applied to the exploration and development practices in the Qingcheng Oilfield. Key findings are obtained in three aspects. First, the seismic progradational reflections, marker tuff beds, and condensed sections of flooding surfaces in the Yanchang Formation are consistent and isochronous. Using flooding surface markers as a reference, a progradational sequence stratigraphic architecture is reconstructed for the middle-upper part of Yanchang Formation, and divided into seven clinoform units (CF1–CF7). Second, progradation predominantly occurs in semi-deep to deep lake environments, with the depositional center not always coinciding with the thickest strata. The lacustrine basin underwent an evolution of “oscillatory regression–progradational infilling- multi-phase superimposition”. Third, the case study of Qingcheng Oilfield reveals that the major pay zones consist of “isochronous but heterochronous” gravity-flow sandstone complexes. Guided by the progradational sequence stratigraphic architecture, horizontal well oil-layer penetration rates remain above 82%. The progradational sequence stratigraphic architecture and associated geological insights are more consistent with the sedimentary infilling mechanisms of large-scale continental depressed lacustrine basins and actual drilling results. The research results provide crucial theoretical and technical support for subsequent refined exploration and development of the Yanchang Formation, and are expected to offer a reference for research and production practice in similar continental lacustrine basins.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 5","pages":"Pages 1164-1178"},"PeriodicalIF":8.0,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145398661","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Transmission mechanism from orbital forced climate change to organic matter and shale oil enrichment: A case study of Gulong shale oil in the Cretaceous Qingshankou Formation, Songliao Basin, NE China","authors":"Huajian WANG ,&nbsp;Zhenwu LIU ,&nbsp;Shan LI ,&nbsp;Yuke LIU ,&nbsp;Shuang GAO ,&nbsp;Yiran LYU ,&nbsp;Huaichun WU ,&nbsp;Shuichang ZHANG","doi":"10.1016/S1876-3804(25)60637-9","DOIUrl":"10.1016/S1876-3804(25)60637-9","url":null,"abstract":"<div><div>Taking the GY8HC well in the Gulong Sag of the Songliao Basin, NE China, as an example, this study utilized high-precision zircon U-Pb ages from volcanic ashes and AstroBayes method to estimate sedimentation rates. Through spectral analysis of high-resolution total organic carbon content (TOC), laboratory-measured free hydrocarbons (<em>S</em>₁), hydrocarbons formed during pyrolysis (<em>S</em>₂), and mineral contents, the enrichment characteristics and controlling factors of shale oil in an overmature area were investigated. The results indicate that: (1) TOC, <em>S</em>₁, and <em>S</em>₂ associated with shale oil enrichment exhibit a significant 173×10³ a obliquity amplitude modulation cycle; (2) Quartz and illite/smectite mixed-layer contents related to lithological composition show a significant 405×10³ a long eccentricity cycle; (3) Comparative studies with the high-maturity GY3HC well and moderate-maturity ZY1 well reveal distinct in-situ enrichment characteristics of shale oil in the overmature Qingshankou Formation, with a significant positive correlation to TOC, indicating that high TOC is a key factor for shale oil enrichment in overmature areas; (4) The sedimentary thickness of 12–13 m corresponding to the 173×10³ a cycle can serve as the sweet spot interval height for shale oil development in the study area, falling within the optimal fracture height range (10–15 m) generated during hydraulic fracturing of the Qingshankou shale. Orbitally forced climate changes not only controlled the sedimentary rhythms of organic carbon burial and lithological composition in the Songliao Basin but also influenced the enrichment characteristics and sweet spot distribution of Gulong shale oil.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 5","pages":"Pages 1222-1234"},"PeriodicalIF":8.0,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145398647","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experiment on proppant transport into fractures of unconventional reservoirs using stereoscopic particle image velocimetry","authors":"Jianchun GUO ,&nbsp;Hengbo ZUO ,&nbsp;Tao ZHANG ,&nbsp;Tang TANG ,&nbsp;Hangyu ZHOU ,&nbsp;Yuxuan LIU ,&nbsp;Mingfeng LI","doi":"10.1016/S1876-3804(25)60646-X","DOIUrl":"10.1016/S1876-3804(25)60646-X","url":null,"abstract":"<div><div>Stereoscopic particle image velocimetry technology was employed to investigate the planar three-dimensional velocity field and the process of proppant entry into branch fractures in a fracture configuration of “vertical main fracture - vertical branch fracture” intersecting at a 90° angle. This study analyzed the effects of pumping rate, fracturing fluid viscosity, proppant particle size, and fracture width on the transport behavior of proppant into branch fractures. Based on the deflection behavior of proppant, the main fractures can be divided into five regions: pre-entry transition, pre-entry stabilization, deflection entry at the fracture mouth, rear absorption entry, and movement away from the fracture mouth. Proppant primarily deflects into the branch fracture at the fracture mouth, with a small portion drawn in from the rear of the intersection. Increasing the pumping rate, reducing the proppant particle size, and widening the branch fracture are conducive to promoting proppant deflection into the branch. With increasing fracturing fluid viscosity, the ability of proppant to enter the branch fracture first improves and then declines, indicating that excessively high viscosity is unfavorable for proppant entry into the branch. During field operations, a high pumping rate and micro- to small-sized proppant can be used in the early stage to ensure effective placement in the branch fractures, followed by medium- to large-sized proppant to ensure adequate placement in the main fracture and enhance the overall conductivity of the fracture network.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 5","pages":"Pages 1340-1350"},"PeriodicalIF":8.0,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145398569","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}