Petroleum Exploration and Development最新文献

{"title":"Lamina combination characteristics and differential shale oil enrichment mechanisms of continental organic-rich shale: A case study of Triassic Yanchang Formation Chang 73 sub-member, Ordos Basin, NW China","authors":"Xiaobing NIU ,&nbsp;Chengfu LYU ,&nbsp;Shengbin FENG ,&nbsp;Qianshan ZHOU ,&nbsp;Honggang XIN ,&nbsp;Yueye XIAO ,&nbsp;Cheng LI ,&nbsp;Weidong DAN","doi":"10.1016/S1876-3804(25)60569-6","DOIUrl":"10.1016/S1876-3804(25)60569-6","url":null,"abstract":"<div><div>The lamina (combination) types, reservoir characteristics and shale oil occurrence states of organic-rich shale in the Triassic Yanchang Formation Chang 7₃ sub-member in the Ordos Basin were systematically investigated to reveal the main controlling factors of shale oil occurrence under different lamina combinations. The differential enrichment mechanisms and patterns of shale oil were discussed using the shale oil micro-migration characterization and evaluation methods from the perspectives of relay hydrocarbon supply, stepwise migration, and multi-stage differentiation. The results are obtained in five aspects. First, Chang 7₃ shale mainly develops five types of lamina combination, i.e. non-laminated shale, sandy laminated shale, tuffaceous laminated shale, mixed laminated shale, and organic-rich laminated shale. Second, shales with different lamina combinations are obviously different in the reservoir space. Specifically, shales with sandy laminae and tuffaceous laminae have a large number of intergranular pores, dissolution pores and hydrocarbon generation-induced fractures. The multi-scale pore and fracture system constitutes the main place for liquid hydrocarbon occurrence. Third, the occurrence and distribution of shale oil in shale with different lamina combinations are jointly controlled by organic matter abundance, reservoir property, thermal evolution degree, mineral composition and laminae scale. The micro-nano-scale pore-fracture networks within shales containing rigid laminae, particularly sandy and tuffaceous laminations, primarily contain free-state light hydrocarbon components. In contrast, adsorption-phase heavy hydrocarbon components predominantly occupy surfaces of organic matter assemblages, clay mineral matrices, and framework mineral particulates. Fourth, there is obvious shale oil micro-migration between shales with different lamina combinations in Chang 7₃. Generally, such micro-migration is stepwise in a sequence of organic-rich laminated shale → tuffaceous laminated shale → mixed laminated shale → sandy lamiated shale → non-laminated shale. Fifth, the relay hydrocarbon supply of organic matter under the control of the spatial superposition of shales with various laminae, the stepwise migration via multi-scale pore and fracture network, and the multi-differentiation in shales with different lamina combinations under the control of organic-inorganic interactions fundamentally decide the differences of shale oil components between shales with different lamina combinations.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 2","pages":"Pages 316-329"},"PeriodicalIF":7.0,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143873168","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":"Main factors controlling unconventional gas enrichment and high production in the first member of Permian Maokou Formation, southeastern Sichuan Basin, SW China","authors":"Guisong HE ,&nbsp;Bin SUN ,&nbsp;Yuqiao GAO ,&nbsp;Peixian ZHANG ,&nbsp;Zhiping ZHANG ,&nbsp;Xiao CAI ,&nbsp;Wei XIA","doi":"10.1016/S1876-3804(25)60575-1","DOIUrl":"10.1016/S1876-3804(25)60575-1","url":null,"abstract":"<div><div>Based on the data of drilling, logging, experiment and gas testing in the Nanchuan area, southeastern Sichuan Basin, the hydrocarbon generation potential, gas genesis, occurrence state, migration, preservation conditions, pore and fracture features and accumulation evolution of the first member of Permian Maokou Formation (Mao 1 Member) are systematically studied, and the main controlling factors of unconventional gas enrichment and high production in marlstone assemblage of Mao 1 Member are discussed. (1) The enrichment and high yield of unconventional natural gas in the Mao 1 Member are controlled by three factors: carbon-rich fabric controlling hydrocarbon generation potential, good preservation controlling enrichment, and natural fracture controlling production. (2) The carbonate rocks of Mao 1 Member with carbon rich fabric have significant gas potential, exhibiting characteristics of self-generation and self-storage, which lays the material foundation for natural gas accumulation. (3) The occurrence state of natural gas is mainly free gas, which is prone to lateral migration, and good storage conditions are the key to natural gas enrichment. Positive structure is more conducive to natural gas accumulation, and a good compartment is created jointly by the self-sealing property of the Mao 1 Member and its top and bottom sealing property in monoclinal area, which is favorable for gas accumulation by retention. (4) Natural fractures are the main reservoir space and flow channel, and the more developed natural fractures are, the more conducive to the formation of high-quality porous-fractured reservoirs and the accumulation of natural gas, which is the core of controlling production. (5) The accumulation model of unconventional natural gas is proposed as “self-generation and self-storage, preservation controlling richness, and fractures controlling production”;. (6) Identifying fracture development areas with good preservation conditions is the key to successful exploration, and implementing horizontal well staged acidizing and fracturing is an important means to increase production and efficiency. The study results are of referential significance for further understanding the natural gas enrichment in the Mao 1 Member and guiding the efficient exploration and development of new types of unconventional natural gas.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 2","pages":"Pages 408-421"},"PeriodicalIF":7.0,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143873785","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":"Visualization simulation experiments and porosity evolution mechanisms of deep to ultra-deep carbonate reservoirs","authors":"Anping HU ,&nbsp;Min SHE ,&nbsp;Anjiang SHEN ,&nbsp;Zhanfeng QIAO ,&nbsp;Wenzheng LI ,&nbsp;Qiuding DU ,&nbsp;Changjian YUAN","doi":"10.1016/S1876-3804(25)60573-8","DOIUrl":"10.1016/S1876-3804(25)60573-8","url":null,"abstract":"<div><div>To address the challenges in studying the pore formation and evolution processes, and unclear preservation mechanisms of deep to ultra-deep carbonate rocks, a high-temperature and high-pressure visualization simulation experimental device was developed for ultra-deep carbonate reservoirs. This unit comprises four core modules: an ultra-high temperature, high pressure triaxial stress core holder module (temperature higher than 300 °C, pressure higher than 150 MPa), a multi-stage continuous flow module with temperature-pressure regulation, an ultra-high temperature-pressure sapphire window cell and an in-situ high-temperature-pressure fluid property measurement module and real-time ultra-high temperature-pressure permeability detection module. Using the new experimental device and the carbonate rock samples from the Sichuan Basin and Tarim Basin to simulate the dissolution-precipitation process of deep to ultra-deep carbonate reservoirs in an analogous geological setting, the geological insights were obtained in three aspects. First, the pore-throat structure of carbonate is controlled by lithology and initial pore-throat structure, and fluid type, concentration and dissolution duration determine the degree of dissolution. The dissolution process exhibits two evolution patterns. The dissolution scale is positively correlated to the temperature and pressure, and the pore-forming peak period aligns well with the hydrocarbon generation peak period. Second, the dissolution potential of dolomite in an open flow system is greater than that of limestone, and secondary dissolved pores formed continuously are controlled by the type and concentration of acidic fluids and the initial physical properties. These pores predominantly distribute along pre-existing pore/fracture zones. Third, in a nearly closed diagenetic system, after the chemical reaction between acidic fluids and carbonate rock reaches saturation and dynamic equilibrium, the pore structure no longer changes, keeping pre-existing pores well-preserved. These findings have important guiding significance for the evaluation of pore-throat structure and development potential of deep to ultra-deep carbonate reservoirs, and the prediction of main controlling factors and distribution of high-quality carbonate reservoirs.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 2","pages":"Pages 377-390"},"PeriodicalIF":7.0,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143873172","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":"Application of the whole petroleum system in the evaluation of the global natural gas hydrate resource","authors":"Xiongqi PANG ,&nbsp;Chengzao JIA ,&nbsp;Zhi XU ,&nbsp;Tao HU ,&nbsp;Liyin BAO ,&nbsp;Tingyu PU","doi":"10.1016/S1876-3804(25)60568-4","DOIUrl":"10.1016/S1876-3804(25)60568-4","url":null,"abstract":"<div><div>Natural gas hydrate (NGH), as a widely recognized clean energy, has shown a significant resource potential. However, due to the lack of a unified evaluation methodology and the difficult determination of key parameters, the evaluation results of global NGH resource are greatly different. This paper establishes a quantitative relationship between NGH resource potential and conventional oil and gas resource and a NGH resource evaluation model based on the whole petroleum system (WPS) and through the analysis of dynamic field controlling hydrocarbon accumulation. The global NGH initially in place and recoverable resources are inverted through the Monte Carlo simulation, and verified by using the volume analogy method based on drilling results and the trend analysis method of previous evaluation results. The proposed evaluation model considers two genetic mechanisms of natural gas (biological degradation and thermal degradation), surface volume conversion factor difference between conventional natural gas and NGH, and the impacts of differences in favorable distribution area and thickness and in other aspects on the results of NGH resource evaluation. The study shows that the global NGH initially in place and recoverable resources are 99×10¹² m³ and 30×10¹² m³, with averages of 214×10¹² m³ and 68×10¹² m³, respectively, less than 5% of the total conventional oil and gas resources, and they can be used as a supplement for the future energy of the world. The proposed NGH resource evaluation model creates a new option of evaluation method and technology, and generates reliable data of NGH resource according to the reliability comprehensive analysis and test, providing a parameter basis for subsequent NGH exploration and development.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 2","pages":"Pages 301-315"},"PeriodicalIF":7.0,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143873167","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":"Formation and preservation of pores in deep limestone reservoirs: A case study of Upper Permian Changxing Formation, central Sichuan Basin, SW China","authors":"Long WEN ,&nbsp;Bing LUO ,&nbsp;Benjian ZHANG ,&nbsp;Xiao CHEN ,&nbsp;Wenzheng LI ,&nbsp;Yifeng LIU ,&nbsp;Anping HU ,&nbsp;Xihua ZHANG ,&nbsp;Anjiang SHEN","doi":"10.1016/S1876-3804(25)60570-2","DOIUrl":"10.1016/S1876-3804(25)60570-2","url":null,"abstract":"<div><div>In recent years, drilling data from wells Pengshen 10, Heshen 9, Tongshen 17 and Zhengyang 1 in the Sichuan Basin have confirmed the presence of a set of porous reef-beach limestone reservoirs in the Upper Permian Changxing Formation, which breaks the traditional view that deep carbonate oil and gas are only distributed in porous dolomite reservoirs and karst fracture-cavity limestone reservoirs. Through core and thin section observations, geochemical analysis, and well-seismic based reservoir identification and tracking, the study on formation mechanism of pores in deep reef-beach limestone reservoirs is carried out, this study provides insights in four aspects. (1) Porous reef-beach limestone reservoirs are developed in the Changxing Formation in deep-buried layers. The reservoir space is composed of intergranular pores, framework pores, intrafossil pores, moldic pores and dissolution pores, which are formed in depositional and epigenetic environments. (2) The intermittently distributed porous reef-beach complexes are surrounded by relatively dense micrite limestone, which leads to the formation of local abnormal high-pressure inside the reef-beach complexes with the temperature increased. (3) The floor of the Changxing Formation reservoir is composed with interbedded tight mudstone and limestone of the Upper Permian Wujiaping Formation, and the roof is the tight micrite limestone interbedded with mudstone of the first member of Lower Triassic Feixianguan Formation. Under the clamping of dense roof and floor, the abnormal high-pressure in the Changxing Formation is formed. Abnormal high-pressure (overpressured compartment) is the key to maintain the pores formed in the depositional and epigenetic environments in deep-buried layers. (4) Based on the identification of roof, floor and reef-beach complexes, the favorable reef-beach limestone reservoir distribution area of 10.3×10⁴ km² is predicted by well-seismic integration. These insights lay the theoretical foundation for the development of deep porous limestone reservoirs, expand the new field of exploration of deep-buried limestone reservoirs in the Sichuan Basin.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 2","pages":"Pages 330-345"},"PeriodicalIF":7.0,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143873169","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":"Evaluation of the adaptability of CO2 pre-fracturing to Gulong shale oil reservoirs, Songliao Basin, NE China","authors":"Zhengdong LEI ,&nbsp;Siwei MENG ,&nbsp;Yingfeng PENG ,&nbsp;Jiaping TAO ,&nbsp;Yishan LIU ,&nbsp;He LIU","doi":"10.1016/S1876-3804(25)60579-9","DOIUrl":"10.1016/S1876-3804(25)60579-9","url":null,"abstract":"<div><div>Based on development practices of Gulong shale oil and a series of experiments on interactions between CO₂ and the rocks and fluids of shale oil reservoirs, the application and adaptability of CO₂ pre-fracturing to the Gulong shale oil reservoirs are systematically evaluated. The pilot tests indicate that compared to wells with conventional fracturing, the wells with CO₂ pre-fracturing demonstrate four significant characteristics: high but rapidly declined initial production, low cumulative production, high and unstable gas-oil ratio, and non-competitive liquid production. These characteristics are attributed to two facts. First, pre-fracturing with CO₂ inhibits the cross-layer extension of the main fractures in the Gulong shale oil reservoirs, reduces the stimulated reservoir volume, weakens the fracture conductivity, and decreases the matrix permeability and porosity, ultimately impeding the engineering performance. Second, due to the confinement effect, pre-fracturing with CO₂ increases the saturation pressure difference between the fracture-macropore system and the matrix micropore system, leading to continuous gas production and light hydrocarbon evaporation in the fracture-macropore system, and difficult extraction of crude oil in the matrix-micropore system, which affects the stable production. Under the superposition of various characteristics of Gulong shale oil reservoirs, pre-fracturing with CO₂ has some negative impacts on reservoir stimulation (fracture extension and fracture conductivity), matrix seepage, and fluid phase and production, which restrict the application performance of CO₂ pre-fracturing in the Gulong shale oil reservoirs.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 2","pages":"Pages 459-470"},"PeriodicalIF":7.0,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143873250","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":"Paleoclimate, paleoenvironment and source rock development model of Eocene in Shunde Sag, Pearl River Mouth Basin, China","authors":"Jianxiang PEI,&nbsp;Qiuyue JIN,&nbsp;Daijun FAN,&nbsp;Mingzhu LEI","doi":"10.1016/S1876-3804(25)60571-4","DOIUrl":"10.1016/S1876-3804(25)60571-4","url":null,"abstract":"<div><div>Based on the comprehensive analysis of data from petrology and mineralogy, well logging, seismic surveys, paleontology, and geochemistry, a detailed research was conducted on paleoenvironmental and paleoclimatic conditions, and modeling of the source rocks in the second member of the Eocene Wenchang Formation (Wen 2 Member) in the Northern Shunde Subsag at the southwestern margin of the Pearl River Mouth Basin. The Wen 2 Member hosts excellent, thick lacustrine source rocks with strong longitudinal heterogeneity and an average total organic carbon (TOC) content of over 4.9%. The Wen 2 Member can be divided into three units (I, II, III) from bottom to top. Unit I features excellent source rocks with Type I organic matters (average TOC of 5.9%) primarily sourced from lake organisms; Unit II hosts source rocks dominated by Type II2 organic matters (average TOC of 2.2%), which are originated from mixed sources dominated by terrestrial input. Unit III contains good to excellent source rocks dominated by Type II1 organic matters (average TOC of 4.9%), which are mainly contributed by lake organisms and partially by terrestrial input. Under the background of rapid subsidence and limited source supply during intense rifting period in the Eocene, excellent source rocks were developed in Wen 2 Member in the Northern Shunde Subsag under the coordinated control of warm and humid climate, volcanic activity, and deep-water reducing conditions. During the deposition of Unit I, the warm and humid climate and volcanic activity promoted the proliferation of lake algaes, primarily Granodiscus, resulting in high initial productivity, and deep-water reducing conditions enabled satisfactory preservation of organic matters. These factors jointly controlled the development and occurrence of excellent source rocks. During the deposition of Unit II, a transition from warm to cool and semi-arid paleoclimatic conditions led to a decrease in lake algaes and initial productivity. Additionally, enhanced terrestrial input and shallow-water, weakly oxidizing water conditions caused a significant dilution and decomposition of organic matters, degrading the quality of source rocks. During the deposition of Unit III, when the paleoclimatic conditions are cool and humid, Pediastrum and Botryococcus began to thrive, leading to an increase in productivity. Meanwhile, the reducing environment of semi-deep water facilitated the preservation of excellent source rocks, albeit slightly inferior to those in Unit I. The study results clarify the differential origins and development models of various source rocks in the Shunde Sag, offering valuable guidance for evaluating source rocks and selecting petroleum exploration targets in similar marginal sags.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 2","pages":"Pages 346-360"},"PeriodicalIF":7.0,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143873170","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":"A shut-in pressure calculation method for high-temperature high-pressure wells in deepwater fractured formations based on thermo-hydro-mechanical coupling","authors":"Gang CHEN ,&nbsp;Zhiyuan WANG ,&nbsp;Xiaohui SUN ,&nbsp;Jie ZHONG ,&nbsp;Jianbo ZHANG ,&nbsp;Xueqi LIU ,&nbsp;Mingwei ZHANG ,&nbsp;Baojiang SUN","doi":"10.1016/S1876-3804(25)60583-0","DOIUrl":"10.1016/S1876-3804(25)60583-0","url":null,"abstract":"<div><div>By comprehensively considering the influences of temperature and pressure on fluid density in high temperature and high pressure (HTHP) wells in deepwater fractured formations and the effects of formation fracture deformation on well shut-in afterflow, this study couples the shut-in temperature field model, fracture deformation model, and gas flow model to establish a wellbore pressure calculation model incorporating thermo-hydro-mechanical coupling effects. The research analyzes the governing patterns of geothermal gradient, bottomhole pressure difference, drilling fluid pit gain, and kick index on casing head pressure, and establishes a shut-in pressure determination chart for HPHT wells based on coupled model calculation results. The study results show: geothermal gradient, bottomhole pressure difference, and drilling fluid pit gain exhibit positive correlations with casing head pressure; higher kick indices accelerate pressure rising rates while maintaining a constant maximum casing pressure; validation against field case data demonstrates over 95% accuracy in predicting wellbore pressure recovery after shut-in, with the pressure determination chart achieving 97.2% accuracy in target casing head pressure prediction and 98.3% accuracy in target shut-in time. This method enables accurate acquisition of formation pressure after HPHT well shut-in, providing reliable technical support for subsequent well control measures and ensuring safe and efficient development of deepwater and deep hydrocarbon reservoirs.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 2","pages":"Pages 506-518"},"PeriodicalIF":7.0,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143873244","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":"Controlling factors and exploration potential of shale gas enrichment and high yield in Permian Dalong Formation, northern Sichuan Basin, SW China","authors":"Rui YONG ,&nbsp;Hongzhi YANG ,&nbsp;Wei WU ,&nbsp;Xue YANG ,&nbsp;Yuran YANG ,&nbsp;Haoyong HUANG","doi":"10.1016/S1876-3804(25)60567-2","DOIUrl":"10.1016/S1876-3804(25)60567-2","url":null,"abstract":"<div><div>Based on the basic data of drilling, logging, testing and geological experiments, the geological characteristics of the Permian Dalong Formation marine shales in the northern Sichuan Basin and the factors controlling shale gas enrichment and high yield are studied. The results are obtained in four aspects. First, the high-quality shale of the Dalong Formation was formed after the deposition of the Permian Wujiaping Formation, and it is developed in the Kaijiang-Liangping trough in the northern part of Sichuan Basin, where deep-water continental shelf facies and deep-water reduction environment with thriving siliceous organisms have formed the black siliceous shale rich in organic matter. Second, the Dalong Formation shale contains both organic and inorganic pores, with stratification of alternated brittle and plastic minerals. In addition to organic pores, a large number of inorganic pores are developed even in ultra-deep (deeper than 4 500 m) layers, contributing a total porosity of more than 5%, which significantly expands the storage space for shale gas. Third, the limestone at the roof and floor of the Dalong Formation acted as seal rock in the early burial and hydrocarbon generation stage, providing favorable conditions for the continuous hydrocarbon generation and rich gas preservation in shale interval. In the later reservoir stimulation process, it was beneficial to the lateral extension of the fractures, so as to achieve the optimal stimulation performance and increase the well-controlled resources. Combining the geological, engineering and economic conditions, the favorable area with depth less than 5 500 m is determined to be 1 800 km², with resources of 5 400×10⁸ m³. Fourth, the shale reservoirs of the Dalong Formation are thin but rich in shale gas. The syncline zone far away from the main faults in the high and steep tectonic zone, eastern Sichuan Basin, with depth less than 5 500 m, is the most favorable target for producing the Permian shale gas under the current engineering and technical conditions. It mainly includes the Nanya syncline, Tanmuchang syncline and Liangping syncline.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 2","pages":"Pages 285-300"},"PeriodicalIF":7.0,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143873166","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":"Intelligent evaluation of sandstone rock structure based on a visual large model","authors":"Yili REN ,&nbsp;Changmin ZENG ,&nbsp;Xin LI ,&nbsp;Xi LIU ,&nbsp;Yanxu HU ,&nbsp;Qianxiao SU ,&nbsp;Xiaoming WANG ,&nbsp;Zhiwei LIN ,&nbsp;Yixiao ZHOU ,&nbsp;Zilu ZHENG ,&nbsp;Huiying HU ,&nbsp;Yanning YANG ,&nbsp;Fang HUI","doi":"10.1016/S1876-3804(25)60586-6","DOIUrl":"10.1016/S1876-3804(25)60586-6","url":null,"abstract":"<div><div>Existing sandstone rock structure evaluation methods rely on visual inspection, with low efficiency, semi-quantitative analysis of roundness, and inability to perform classified statistics in particle size analysis. This study presents an intelligent evaluation method for sandstone rock structure based on the Segment Anything Model (SAM). By developing a lightweight SAM fine-tuning method with rank-decomposition matrix adapters, a multispectral rock particle segmentation model named CoreSAM is constructed, which achieves rock particle edge extraction and type identification. Building upon this, we propose a comprehensive quantitative evaluation system for rock structure, assessing parameters including particle size, sorting, roundness, particle contact and cementation types. The experimental results demonstrate that CoreSAM outperforms existing methods in rock particle segmentation accuracy while showing excellent generalization across different image types such as CT scans and core photographs. The proposed method enables full-sample, classified particle size analysis and quantitative characterization of parameters like roundness, advancing reservoir evaluation towards more precise, quantitative, intuitive, and comprehensive development.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 2","pages":"Pages 548-558"},"PeriodicalIF":7.0,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143873247","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}