Pub Date : 2025-10-01DOI: 10.1016/S1876-3804(25)60643-4
Zhaohui ZHOU , Xiaojie ZHANG , Qun ZHANG , Ninghong JIA , Lu HAN , Lei ZHANG , Lu ZHANG , Weifeng LYU
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.
{"title":"New high-efficiency system for improving oil recovery based on the superwetting phenomenon","authors":"Zhaohui ZHOU , Xiaojie ZHANG , Qun ZHANG , Ninghong JIA , Lu HAN , Lei ZHANG , Lu ZHANG , 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-C<sub>13</sub>PO<sub>13</sub>S) 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-C<sub>13</sub>PO<sub>13</sub>S 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-C<sub>13</sub>PO<sub>13</sub>S 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-C<sub>13</sub>PO<sub>13</sub>S 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}
Pub Date : 2025-10-01DOI: 10.1016/S1876-3804(25)60645-8
Haijun YANG , Chunsheng WANG , Xianzhang YANG , Zhi ZHANG , Xuguang GUO , Chonghao SUN , Xiaogang LYU , Jinlong LIU
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.
{"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 , Chunsheng WANG , Xianzhang YANG , Zhi ZHANG , Xuguang GUO , Chonghao SUN , Xiaogang LYU , 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}
Pub Date : 2025-10-01DOI: 10.1016/S1876-3804(25)60632-X
Xiuqin DENG , Bin BAI
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 & 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 7th 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.
{"title":"Whole petroleum system and main controlling factors of hydrocarbon accumulation in the Mesozoic of Ordos Basin, NW China","authors":"Xiuqin DENG , 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 & 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<sup>th</sup> 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}
Pub Date : 2025-10-01DOI: 10.1016/S1876-3804(25)60634-3
Yuan NENG , Zhou XIE , Longfei SHAO , Qiqi RUAN , Pengfei KANG , Jianan ZHANG , Zhiwen TIAN , Genji LIU
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.
{"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 , Zhou XIE , Longfei SHAO , Qiqi RUAN , Pengfei KANG , Jianan ZHANG , Zhiwen TIAN , 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}
Pub Date : 2025-10-01DOI: 10.1016/S1876-3804(25)60633-1
Xiao HUI , Yunchao HOU , Tong QU , Jie ZHANG , Zhi YANG
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.
{"title":"Progradational sequence stratigraphic architecture of the Triassic Yanchang Formation and a case study of Qingcheng Oilfield, Ordos Basin, NW China","authors":"Xiao HUI , Yunchao HOU , Tong QU , Jie ZHANG , 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}
Pub Date : 2025-10-01DOI: 10.1016/S1876-3804(25)60637-9
Huajian WANG , Zhenwu LIU , Shan LI , Yuke LIU , Shuang GAO , Yiran LYU , Huaichun WU , Shuichang ZHANG
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 (S1), hydrocarbons formed during pyrolysis (S2), and mineral contents, the enrichment characteristics and controlling factors of shale oil in an overmature area were investigated. The results indicate that: (1) TOC, S1, and S2 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.
{"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 , Zhenwu LIU , Shan LI , Yuke LIU , Shuang GAO , Yiran LYU , Huaichun WU , 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><sub>1</sub>), hydrocarbons formed during pyrolysis (<em>S</em><sub>2</sub>), 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><sub>1</sub>, and <em>S</em><sub>2</sub> associated with shale oil enrichment exhibit a significant 173×10<sup>3</sup> a obliquity amplitude modulation cycle; (2) Quartz and illite/smectite mixed-layer contents related to lithological composition show a significant 405×10<sup>3</sup> 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 173×10<sup>3</sup> 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}
Pub Date : 2025-10-01DOI: 10.1016/S1876-3804(25)60640-9
Fugui LIU , Yongfei YANG , Haiyuan YANG , Liu TAO , Yunwei TAO , Kai ZHANG , Hai SUN , Lei ZHANG , Junjie ZHONG , Jun YAO
Existing imaging techniques cannot simultaneously achieve high resolution and a wide field of view, and manual multi-mineral segmentation in shale lacks precision. To address these limitations, we propose a comprehensive framework based on generative adversarial network (GAN) for characterizing pore structure properties of shale, which incorporates image augmentation, super-resolution reconstruction, and multi-mineral auto-segmentation. Using real 2D and 3D shale images, the framework was assessed through correlation function, entropy, porosity, pore size distribution, and permeability. The application results show that this framework enables the enhancement of 3D low-resolution digital cores by a scale factor of 8, without paired shale images, effectively reconstructing the unresolved fine-scale pores under a low resolution, rather than merely denoising, deblurring, and edge clarification. The trained GAN-based segmentation model effectively improves manual multi-mineral segmentation results, resulting in a strong resemblance to real samples in terms of pore size distribution and permeability. This framework significantly improves the characterization of complex shale microstructures and can be expanded to other heterogeneous porous media, such as carbonate, coal, and tight sandstone reservoirs.
{"title":"Pore structure properties characterization of shale using generative adversarial network: Image augmentation, super-resolution reconstruction, and multi-mineral auto-segmentation","authors":"Fugui LIU , Yongfei YANG , Haiyuan YANG , Liu TAO , Yunwei TAO , Kai ZHANG , Hai SUN , Lei ZHANG , Junjie ZHONG , Jun YAO","doi":"10.1016/S1876-3804(25)60640-9","DOIUrl":"10.1016/S1876-3804(25)60640-9","url":null,"abstract":"<div><div>Existing imaging techniques cannot simultaneously achieve high resolution and a wide field of view, and manual multi-mineral segmentation in shale lacks precision. To address these limitations, we propose a comprehensive framework based on generative adversarial network (GAN) for characterizing pore structure properties of shale, which incorporates image augmentation, super-resolution reconstruction, and multi-mineral auto-segmentation. Using real 2D and 3D shale images, the framework was assessed through correlation function, entropy, porosity, pore size distribution, and permeability. The application results show that this framework enables the enhancement of 3D low-resolution digital cores by a scale factor of 8, without paired shale images, effectively reconstructing the unresolved fine-scale pores under a low resolution, rather than merely denoising, deblurring, and edge clarification. The trained GAN-based segmentation model effectively improves manual multi-mineral segmentation results, resulting in a strong resemblance to real samples in terms of pore size distribution and permeability. This framework significantly improves the characterization of complex shale microstructures and can be expanded to other heterogeneous porous media, such as carbonate, coal, and tight sandstone reservoirs.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 5","pages":"Pages 1262-1274"},"PeriodicalIF":8.0,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145398552","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}
Pub Date : 2025-10-01DOI: 10.1016/S1876-3804(25)60646-X
Jianchun GUO , Hengbo ZUO , Tao ZHANG , Tang TANG , Hangyu ZHOU , Yuxuan LIU , Mingfeng LI
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.
{"title":"Experiment on proppant transport into fractures of unconventional reservoirs using stereoscopic particle image velocimetry","authors":"Jianchun GUO , Hengbo ZUO , Tao ZHANG , Tang TANG , Hangyu ZHOU , Yuxuan LIU , 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}
Pub Date : 2025-10-01DOI: 10.1016/S1876-3804(25)60630-6
Caiwei FAN , Bing XIE , Fanghao XU , Ming LI , Guosheng XU , Gang ZHOU , Xichun ZHANG , Anran LI
Based on drilling, mud logging, core, seismic and imaging logging data, this paper studies the identification and evolution process of negative inversion structures in the Carboniferous buried hills in the No. 1 and No. 2 fault zones of Weixinan Sag, Beibu Gulf Basin, China, and reveals the controls of these structures on high-quality reservoirs. The No. 2 fault zone develops significant negative inversion structures in the Carboniferous buried hills, as a result of multi-stage transformations of compressive–tensile stress fields in the period from the Late Hercynian to the Himalayan. The Hercynian carbonates laid the material basis for the formation of high-quality reservoirs. The negative inversion structures mainly control the development of high-quality reservoirs in buried hills through: (1) creating large-scale fractures to increase reservoir space and improve oil-gas flow pathways; (2) regulating stratigraphic differential denudation to highlight dominant lithology for later reservoir transformation; (3) shaping the paleogeomorphological highlands to provide favorable conditions for superficial karstification. The negative inversion structures form a high-quality, composite reservoir space with the synergistic existence of superficial dissolution fractures/cavities and burial-enhanced karst systems through the coupling of fracture network creation, formation denudation screening and multi-stage karst transformation. The research results have guided the breakthrough of the first exploratory well with a daily oil production over 1 000 m3 in carbonate buried-hill reservoir in the Beibu Gulf Basin, and provide referential geological basis for finding more reserves and achieving higher production in the Carboniferous buried hills in the Weixinan Sag.
{"title":"Control of negative inversion structures on high-quality Carboniferous buried hill reservoirs in the Weixinan Sag, Beibu Gulf Basin, China","authors":"Caiwei FAN , Bing XIE , Fanghao XU , Ming LI , Guosheng XU , Gang ZHOU , Xichun ZHANG , Anran LI","doi":"10.1016/S1876-3804(25)60630-6","DOIUrl":"10.1016/S1876-3804(25)60630-6","url":null,"abstract":"<div><div>Based on drilling, mud logging, core, seismic and imaging logging data, this paper studies the identification and evolution process of negative inversion structures in the Carboniferous buried hills in the No. 1 and No. 2 fault zones of Weixinan Sag, Beibu Gulf Basin, China, and reveals the controls of these structures on high-quality reservoirs. The No. 2 fault zone develops significant negative inversion structures in the Carboniferous buried hills, as a result of multi-stage transformations of compressive–tensile stress fields in the period from the Late Hercynian to the Himalayan. The Hercynian carbonates laid the material basis for the formation of high-quality reservoirs. The negative inversion structures mainly control the development of high-quality reservoirs in buried hills through: (1) creating large-scale fractures to increase reservoir space and improve oil-gas flow pathways; (2) regulating stratigraphic differential denudation to highlight dominant lithology for later reservoir transformation; (3) shaping the paleogeomorphological highlands to provide favorable conditions for superficial karstification. The negative inversion structures form a high-quality, composite reservoir space with the synergistic existence of superficial dissolution fractures/cavities and burial-enhanced karst systems through the coupling of fracture network creation, formation denudation screening and multi-stage karst transformation. The research results have guided the breakthrough of the first exploratory well with a daily oil production over 1 000 m<sup>3</sup> in carbonate buried-hill reservoir in the Beibu Gulf Basin, and provide referential geological basis for finding more reserves and achieving higher production in the Carboniferous buried hills in the Weixinan Sag.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 5","pages":"Pages 1128-1139"},"PeriodicalIF":8.0,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145398658","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}
Pub Date : 2025-10-01DOI: 10.1016/S1876-3804(25)60635-5
Jinmin SONG , Junke WANG , Shugen LIU , Long WEN , Yuehao YE , Bing LUO , Zhiwu LI , Benjian ZHANG , Xin JIN , Di YANG , Xihua ZHANG , Jiarui WANG , Gang ZHOU , Jiaxin GUO , Zhaoyi ZHANG , Ping LUO
The occurrence types and controlling factors of organic matter in the sepiolite-containing successions of the first member of Mid-Permian Maokou Formation (Mao-1 Member for short) in the Eastern Sichuan Basin, SW China, have been investigated through outcrop section measurement, core observation, thin section identification, argon ion polishing-field scanning electron microscopy, energy spectrum analysis, X-ray diffraction, total organic carbon content (TOC), major and trace element analysis. Finally the symbiotic adsorption model of sepiolite for organic matter enrichment has been established. The results show that the sepiolite-containing successions of the Mao-1 Member are composed of the rhythmite of mudstone, argillaceous limestone and limestone, with five depositional intervals vertically and the organic matter mostly developed in the mudstone and argillaceous limestone layers within the lower three intervals. The organic matter occurrence types are mostly layered or nodular in macro to meso-scale, blocky-vein-like under a microscope, but scattered, interstitial or adsorbed at a mesoscopic scale. It underwent transition processes from lower to higher salinity, from oxygen-poor and anoxic reduction to oxygen-poor and localized oxygen enrichment on the palaeo-environment of the Mao-1 Member. The first two intervals of the early depositional phase of Mao-1 Member constitute the cyclothems of mudstone, argillaceous limestone and limestone and quantities of fibrous-feathered sepiolite settle down within the Tongjiang-Changshou sag with continuous patchy organic matter from adsorption of alginate by sepiolite in intercrystalline, bedding surfaces and interlayer pores. The third and fourth intervals in the mid-depositional phase are mostly composed of the mudstone and argillaceous limestone alternations with the continuous patchy or banded organic matter in the surface and inter-crystalline pores of fibrous, feathered and flaky sepiolite. And the fifth interval in the late depositional phase of the Mao-1 Member comprises the cyclothems of extremely thin layered argillaceous limestone and thick-layered limestone with the fibrous sepiolite depositing in the argillaceous limestone and irregular organic matter dispersing around the sepiolite. Therefore, the symbiotic adsorption between organic matter and sepiolite effectively enhances the preservation efficiency of organic matter and improves the source rock quality of the Mao-1 Member, which enhances our understanding on the enrichment model of the depositional organic matter.
{"title":"Occurrence types and enrichment model of organic matter in the sepiolite-containing successions: A case study of the first member of Mid-Permian Maokou Formation, Eastern Sichuan Basin, SW China","authors":"Jinmin SONG , Junke WANG , Shugen LIU , Long WEN , Yuehao YE , Bing LUO , Zhiwu LI , Benjian ZHANG , Xin JIN , Di YANG , Xihua ZHANG , Jiarui WANG , Gang ZHOU , Jiaxin GUO , Zhaoyi ZHANG , Ping LUO","doi":"10.1016/S1876-3804(25)60635-5","DOIUrl":"10.1016/S1876-3804(25)60635-5","url":null,"abstract":"<div><div>The occurrence types and controlling factors of organic matter in the sepiolite-containing successions of the first member of Mid-Permian Maokou Formation (Mao-1 Member for short) in the Eastern Sichuan Basin, SW China, have been investigated through outcrop section measurement, core observation, thin section identification, argon ion polishing-field scanning electron microscopy, energy spectrum analysis, X-ray diffraction, total organic carbon content (TOC), major and trace element analysis. Finally the symbiotic adsorption model of sepiolite for organic matter enrichment has been established. The results show that the sepiolite-containing successions of the Mao-1 Member are composed of the rhythmite of mudstone, argillaceous limestone and limestone, with five depositional intervals vertically and the organic matter mostly developed in the mudstone and argillaceous limestone layers within the lower three intervals. The organic matter occurrence types are mostly layered or nodular in macro to meso-scale, blocky-vein-like under a microscope, but scattered, interstitial or adsorbed at a mesoscopic scale. It underwent transition processes from lower to higher salinity, from oxygen-poor and anoxic reduction to oxygen-poor and localized oxygen enrichment on the palaeo-environment of the Mao-1 Member. The first two intervals of the early depositional phase of Mao-1 Member constitute the cyclothems of mudstone, argillaceous limestone and limestone and quantities of fibrous-feathered sepiolite settle down within the Tongjiang-Changshou sag with continuous patchy organic matter from adsorption of alginate by sepiolite in intercrystalline, bedding surfaces and interlayer pores. The third and fourth intervals in the mid-depositional phase are mostly composed of the mudstone and argillaceous limestone alternations with the continuous patchy or banded organic matter in the surface and inter-crystalline pores of fibrous, feathered and flaky sepiolite. And the fifth interval in the late depositional phase of the Mao-1 Member comprises the cyclothems of extremely thin layered argillaceous limestone and thick-layered limestone with the fibrous sepiolite depositing in the argillaceous limestone and irregular organic matter dispersing around the sepiolite. Therefore, the symbiotic adsorption between organic matter and sepiolite effectively enhances the preservation efficiency of organic matter and improves the source rock quality of the Mao-1 Member, which enhances our understanding on the enrichment model of the depositional organic matter.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 5","pages":"Pages 1193-1208"},"PeriodicalIF":8.0,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145398663","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}
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