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Fu Jinhua, Wang Long, Chen Xiu, Liu Jiangyan, Hui Xiao, Cheng Dangxing Progress and prospects of shale oil exploration and development in the seventh member of Yanchang Formation in Ordos Basin China Petroleum Exploration    2023, 28 (5): 1-14.   DOI: 10.3969/j.issn.1672-7703.2023.05.001 Abstract （1029）   HTML    PDF （8745KB）（15）    Knowledge map    Save As an important replacement resource, shale oil is a major exploration field widely concerned at home and abroad. The long-term exploration and development practice enabled to make significant breakthrough and progress in the exploration, development and research of shale oil in the seventh member of Yanchang Formation (Chang 7 member) in Ordos Basin: (1) On the basis of exploration breakthrough in the interlayered type shale oil and discovery of the first integral one-billion-ton level Qingcheng Oilfield, the large-scale and benefit development has been achieved, and a million-ton level national shale oil development demonstration zone has been constructed. (2) In the exploration of the laminated type shale oil, four types of laminated type have been classified of the fine-grained sedimentary complex for the first time, i.e., sandy lamina, tuffaceous lamina, high TOC argillaceous lamina, and medium-low TOC argillaceous lamina. The combination of sandy lamina and medium-low TOC argillaceous lamina is the optimal “sweet spot” interval of the laminated shale oil by evaluating their development scale, reservoir performance, oil-bearing property, movability, and crude oil properties. For the sweet spot interval, new logging evaluation methods such as M- N cross plot are used to finely interpret the complex lithology, and the directional perforation and cross-layer stereoscopic fracturing technology enable to achieve the spatial communication of sweet spots around the wellbore in horizontal section, forming technologies for the effective identification, prediction of sweet spots and reconstruction of the laminated type shale oil, and achieving a major breakthrough in risk exploration, with the primarily submitted predicted shale oil reserves of 2.05×10 8 t. (3) The laminar type shale oil is subdivided into two categories. The medium-high maturity organic shale can be developed by horizontal well, and relatively high TOC (4%-14%) and high S 1 content are key indicators for screening favorable sweet spots. While the medium-low maturity organic shale is the most favorable target for in-situ transformation research. The strategic breakthrough has been made in the exploration of continental shale oil in Chang 7 member in Ordos Basin, which is a milestone in China’s petroleum exploration and development history, but it still faces great challenges. For example, the large-scale and benefit development has been achieved of the interlayered type shale oil, but further research should be conducted on the prediction of sweet spots, production increase and efficiency improvement, and enhanced oil recovery. The laminated type shale oil is facing more challenges and greater difficulty in benefit utilization due to the completely different sedimentary settings, lithologic combination, reservoir space, and engineering quality from the interlayered type shale oil. Therefore, by focusing on the reserve quality and oil movability, hydrocarbon accumulation law should continuously be studied and the research on supporting technology should be strengthened. While for the laminar type shale oil with relative low level of exploration and understanding, the theoretical research and pilot test should steadily be promoted. Reference | Related Articles | Metrics

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Lei Qun, Weng Dingwei, Cai Bo, He Chunming, Shi Yang, Ma Zeyuan Progress, key challenges and countermeasures of reservoir stimulation technology of PetroChina China Petroleum Exploration    2023, 28 (5): 15-27.   DOI: 10.3969/j.issn.1672-7703.2023.05.002 Abstract （515）   HTML    PDF （1123KB）（8）    Knowledge map    Save In order to guarantee the policy of national energy resources security and accelerate domestic oil and gas production, confronting growing complex exploration objects, innovation and advance in reservoir stimulation are the most significant drivers for discovering resources and increasing reserves. By comprehensively reviewing the development history of reservoir stimulation and analyzing technical challenges for exploration target characteristics of PetroChina Company Limited (PetroChina), main progress of reservoir stimulation is systematically summarized, including the optimized design of fracture-controlled stimulation to maximize the release of reserves, the increasing operational capability of fracturing equipment, more robust downhole tools, lower cost of fracturing fluid and improved personalization, and the obvious trend of proppant to low-cost and small mesh size. The supporting role of reservoir stimulation for exploration discovery is clarified. A comprehensive analysis of the key problems faced by hydraulic fracturing is conducted in four aspects: i.e., primary elements of fracturing, fracturing design optimization, field operation quality, and technology evolution. Specifically, the countermeasures in four aspects are proposed: (1) igniting innovation of basic research to provide theoretical support for the progress of fracturing technology; (2) promoting the quality of five primary elements to support the high-quality development of reservoir stimulation technology; (3) promoting the precise technical scheme to provide guidance for more efficient exploration and development of oil and gas; (4) increasing the efficiency of technical management to create a new mode of efficient treatment of engineering management. Reference | Related Articles | Metrics

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Zhao Wenzhi, Zhu Rukai, Zhang Jingya, Yang Jingru Classification, exploration and development status and development trend of continental shale oil in China China Petroleum Exploration    2023, 28 (4): 1-13.   DOI: 10.3969/j.issn.1672-7703.2023.04.001 Abstract （409）   HTML    PDF （970KB）（6）    Knowledge map    Save By comprehensively analyzing the current classification scheme of shale oil at home and abroad, and comparing the exploration and development history, shale oil reserves and output status, and production performance of horizontal wells in China and the United States, the differences in geological conditions, resource quality, recoverability, economy and scale of shale oil between the two countries are analyzed. It is proposed to define the continental shale oil zones in China by using the nomenclature of “geographical location + shale oil” or “geographical location + stratigraphic unit + shale oil”. Furthermore, the shale oil types are classified according to two levels: Firstly, the shale oil is divided into three types based on the sandstone-to-formation ratio (the ratio of source rock to reservoir) or sedimentary facies zones, namely tight oil type shale oil, transitional type shale oil, and pure shale oil; Then the pure shale oil is further subdivided into medium-high mature shale oil and medium-low mature shale oil, or in another way, it is subdivided into light oil, thin oil, heavy oil, and viscous oil zones based on the maturity or oil properties. For the medium-high mature continental shale oil targets, efforts should be focused on the evaluation of enrichment zones/intervals in high-pressure zones, as well as trial production, and research on optimal production technology before 2025, so as to reduce costs to the maximum extent and improve initial single-well production and cumulative output. It is estimated that the annual shale oil output in China will be 600×104t to 1000×10 4t. During the 2025-2035, technology will be further upgraded and optimized to reduce costs, and the annual shale oil output is expected to be 1200×10 4t to 1500×10 4t, growing to be a major supplement to crude oil production with an annual capacity of 2×10 8t/a. As for medium-low mature shale oil, pilot test on the in-situ conversion of shale oil in Chang 7 3 sub-member in Ordos Basin is focused at present; At around 2030, the critical equipment and core technologies will be localized hopefully, and the large-scale and commercial development of shale oil will be achieved, with an annual shale oil output of ten millions of tons. Reference | Related Articles | Metrics

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Wu Yugen, Men Xiangyong, Lou Yu New progress and prospect of coalbed methane exploration and development in China during the 14 th Five-Year Plan period China Petroleum Exploration    2024, 29 (1): 1-13.   DOI: 10.3969/j.issn.1672-7703.2024.01.001 Abstract （399）   HTML    PDF （3914KB）（4）    Knowledge map    Save The development of coalbed methane (CBM) helps to achieve the goal of peak carbon and carbon neutrality as early as possible, and the industrialization of CBM development has basically been achieved in China. However, restricted by theoretical and technological factors, the development scale does not match the abundant resources. Since the 14 th Five-Year Plan period, new progress has been made in CBM exploration and development, including five aspects: (1) The large-scale development of deep CBM has begun in China, and the growth rate of CBM output has significantly accelerated; (2) Major breakthrough has been made the exploration and development of deep CBM, greatly expanding the space for industrial development; (3) Remarkable results have been achieved in reservoir stimulation and reconstruction of difficult to recover resources such as low-efficiency areas and thin coal seams in mature gas fields; (4) Compared with the 13 th Five-Year Plan period, the research focus has shifted from medium-shallow to deep CBM, great innovations have been made in CBM development theory and technology represented by large-scale horizontal well multi-stage fracturing technology in four aspects of geological understanding, drilling and completion, fracturing, and drainage and production, significantly increasing the gas production; (5) The policy environment of CBM industry has continuously been optimized. The preliminary study shows that China has abundant deep CBM resources, and deep CBM resources with a burial depth of greater than 1500 m are more than twice as those with a burial depth of small than 1500 m; The proven CBM reserves in China are dominated by middle-shallow CBM, but the recovery rate is only 7%, indicating considerable remaining resources. In addition, there are abundant CBM resources in thin coal seams in the mature gas fields, which are the realistic replacement resources. Therefore, the major breakthrough of deep CBM and the successful reservoir stimulation and reconstruction in mature gas fields have become the main driving force leading the rapid development of CBM industry, which have shown promising prospects. Based on the research results by several institutions and experts, it is expected that CBM output in China will reach 100×10 8 m 3 in 2025 and 300×10 8 m 3 in 2035. On the other hand, CBM development in China is faced with many challenges. For example, the geological theory and understanding in the new fields of deep CBM and thin coal seams need to be deeply and systematically studied, exploration and development engineering technology for deep CBM is still in the research stage, and the policy support for industrial development still needs improvement. Therefore, it is suggested to strengthen risk CBM exploration and favorable zone selection and evaluation in new fields, strengthen theoretical and technical research on high-efficiency CBM exploration and development, and strengthen policy support and development guidance for CBM industry. Reference | Related Articles | Metrics

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Wang Qinhua, Yang Haijun, Cai Zhenzhong, Li Yong, Yang Xianzhang, Chen Cai, Chen Changchao Exploration breakthrough and significance of Ordovician fault controlled karst hydrocarbon reservoirs of Well Luotan1 in Maigaiti Slope of Tarim Basin China Petroleum Exploration    2024, 29 (2): 1-15.   DOI: 10.3969/j.issn.1672-7703.2024.02.001 Abstract （356）      PDF （9238KB）（24）    Knowledge map    Save The Luotan1 well in the Maigaiti slope of Tarim Basin has made a new breakthrough in the Ordovician carbonate rocks, marking the first exploration breakthrough of a new type of Ordovician fault controlled karst carbonate reservoirs in the Maigaiti slope and marking the discovery of an important strategic replacement area in the slope area. Based on regional drilling, logging, seismic and other data, a comprehensive analysis of the laboratory data of well Luotan1 is carried out to further understand the reservoir formation conditions of Ordovician carbonate rocks in the Maigaiti slope. The formation of Ordovician carbonate fault controlled karst reservoirs in the Maigaiti slope is mainly related to strike slip fault activity, and is one of the three main reservoir formation models in the Maigaiti slope. At present, it has been discovered that hydrocarbon in the Maigaiti slope comes from the source rocks of the Cambrian Yuertus Formation, and the basement paleostructure controls the sedimentation and distribution of the Lower Cambrian source rocks. The slope area has three stages of hydrocarbon charging and accumulation: the Caledonian, Hercynian-Indosinian, and Himalayan periods. Hydrocarbon source rocks, paleotectonic evolution, and the faults connecting hydrocarbon source rocks control the multi-stage hydrocarbon accumulation. The fault active stages and fault penetrating layers determine the hydrocarbon enrichment layers and reservoir properties. The Maigaiti slope is characterized by well-developed Ordovician strike slip faults, with an extension distance of over 1000km, which control the distribution of fault controlled karst carbonate reservoirs and hydrocarbon reservoirs. It has clear zoning characteristics on the plane, with a large resource scale and strong deployability, demonstrating huge exploration potential. It is an important practical field for large-scale hydrocarbon exploration discovery and strategic succession in the southwestern Tarim Basin. Related Articles | Metrics

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Wang Qinghua, Yang Haijun, Cai Zhenzhong, Yang Xianzhang, Zhang Liang, Jiang Jun, Zhou Lu Major breakthrough and significance of petroleum exploration in Well Tuotan 1 on the south slope of Kuqa Depression, Tarim Basin China Petroleum Exploration    2023, 28 (5): 28-42.   DOI: 10.3969/j.issn.1672-7703.2023.05.003 Abstract （293）   HTML    PDF （23060KB）（4）    Knowledge map    Save A major breakthrough has been made in the Cambrian buried hill dolomite reservoir in Well Tuotan 1 in Wensu-Xiqiu area on the south slope of Kuqa Depression in Tarim Basin, which is of great significance to the exploration of multi-target buried hill on the hydrocarbon facing side on the south slope of Kuqa Depression. Due to the complex geological conditions, there is a lack of clear understanding on hydrocarbon enrichment law, and it is difficult to identify geological structures and characterize traps, which restrict the petroleum exploration in the buried hills in the study area. Based on the systematic analysis of structural features, stratigraphic distribution in buried hill, source rock-reservoir-cap rock assemblage, hydrocarbon transport system, and exploration practice, a new pattern of hydrocarbon accumulation in the buried hill has been established. The Paleozoic structure in Wensu-Xiqiu area is a back thrust structure controlled by the front thrust Shajingzi-Xiqiu Fault and recoil thrust Wushinan Fault, which is further complicated by two secondary back thrust faults F1 and F2, forming three rows of Paleozoic buried hill structures, with the stratigraphic age from old to new from the near fault to the far fault area in each row of structures. Among them, the Cambrian buried hill strata have the largest distribution range in a NEE direction. The buried hill reservoirs are mainly composed of dolomite of restricted platform granular beach facies, and the high-quality fractured-vuggy type dolomite reservoirs are contiguously distributed after reconstructed by multi stage tectonic activities and long-term exposure and erosion. The hydrocarbon accumulation assemblage of the buried hill oil and gas reservoirs is composed of dual hydrocarbon supply by mudstone source rocks in the Triassic Huangshanjie Formation and the Jurassic Chakmak Formation, fractured-vuggy type dolomite reservoir, and cap rock of the overlying Paleogene gypsum salt rock; The hydrocarbon accumulation is characterized by “distant hydrocarbon supply from Kuqa Depression, hydrocarbon transport by unconformity surface, and hydrocarbon enrichment in structures on the hydrocarbon facing side”, with the main hydrocarbon accumulation period in the late Himalayan (4-1Ma). The successful drilling of Well Tuotan 1 has confirmed the huge exploration potential of multi-row and multi-type buried hills in Wensu-Xiqiu area, with the re delineated buried hill trap area of 840km 2, and the discovered oil resources of about 2.0×10 8t and natural gas resources of about 590×10 8m 3, which is expected to be a new strategic replacement area for increasing oil and gas reserves and production. Reference | Related Articles | Metrics

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Liu Guoyong, Song Yong, Mao Xinjun, Tang Yong, Guo Xuguang, Wei Yanzhao, Gong Deyu Main strategies and orientations for high-efficiency exploration in Junggar Basin China Petroleum Exploration    2024, 29 (1): 47-64.   DOI: 10.3969/j.issn.1672-7703.2024.01.004 Abstract （285）   HTML    PDF （9200KB）（1）    Knowledge map    Save The petroleum exploration in Junggar Basin has entered a new stage of exploration in hydrocarbon rich sags, which faces new challenges such as increasing burial depth, more scattered and subtle exploration targets, poorer reservoir porosity and permeability, and low upgrade rate and recovery rate of reserves. It is an urgent task to improve exploration effectiveness and achieve benefit development of oil fields. The new round of integrated research and re-understanding of the basin indicates that the spatial distribution of multiple source kitchens in Junggar Basin are complementary, showing “abundant oil and rich gas”, which has broken through the traditional understanding of “abundant oil but less gas” in the basin; There are four types of large-scale effective reservoirs in hydrocarbon rich sags, with orderly distribution in lateral and superposition in vertical direction; Three types of hydrocarbon accumulation systems are identified, such as orderly accumulation of conventional and unconventional oil and gas in source rock, large-scale hydrocarbon accumulation in regressive fan delta facies glutenites above source rock, and stereoscopic hydrocarbon accumulation in medium-shallow fault-sand coupling reservoirs. In combination with the resource characteristics, new geological knowledge, adaptability of exploration and development technologies, and goal of sustainable and benefit development in Junggar Basin, strategies for high-efficiency exploration are proposed, including “simultaneous exploration of oil and gas, emphasis on both conventional and unconventional oil and gas, co-exploration of deep and shallow oil and gas, and reserve increase in multiple fields”, and three major exploration orientations and nine major exploration fields are put forward, so as to support the benefit and sustainable development of the oilfield. Reference | Related Articles | Metrics

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Ni Xinfeng, Liu Junping, Xiang Fengyun, Zhang Ying, Guo Mozhen, Wang Xiaoxing, Wang Xia Competitive transfer reform of oil and gas exploration rights in China and innovative practice of oil and gas enterprises China Petroleum Exploration    2023, 28 (6): 25-36.   DOI: 10.3969/j.issn.1672-7703.2023.06.004 Abstract （268）   HTML    PDF （692KB）（2）    Knowledge map    Save In recent years, the reform of national oil and gas market system has continuously been deepened, and competitive transfer has become the main method to acquire new exploration rights. Since the implementation of the “Opinions on Several Issues Concerning the Promotion of Mineral Resources Management Reform (Trial)” (Natural Resources Regulation (2019) No. 7 ), the government has listed and transferred 66 oil and gas exploration rights for 14 rounds, with an area of 4.19×10 4km 2 and a total transaction price of 9.316 billion RMB. Based on the review of the reform process of national mineral resources management, the characteristics of the reform of exploration rights transfer system in different stages, the innovative measures of oil and gas enterprises to actively participate in the reform, and the exploration practice in the competitive transferred blocks are systematically studied. The results show that: (1) The reform of exploration rights transfer system is divided into three stages, i.e., pilot oil and gas reform, issuance of competitive transfer policy, and full implementation of competitive transfer, showing specified characteristics in each stage. (2) In order to actively respond to the fierce competition, PetroChina and other enterprises have innovated management measures, established rapid response mechanism and management system for the competitive transfer, and formed a set of assessment methods and technical processes for evaluating the block value. (3) Some good results have been achieved in the exploration practice in the transferred blocks. However, except for capacity construction in Wensu block by Zhongman Petroleum, the overall oil and gas discovery is few, and most of the blocks have been withdrawn. The competitive transfer of oil and gas exploration rights has played an important role in promoting exploration investment of enterprises and ensuring national energy security, initially forming diversified oil and gas market. In order to realize the high-efficiency utilization of resources, and truly realize the win-win situation of ensuring national energy security and effectively cultivating healthy competition in oil and gas exploration rights market, several suggestions are put forward, including further improving the competitive transfer management system, establishing a national energy security base, and conducting post-evaluation of the transferred blocks. Reference | Related Articles | Metrics

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Wang Qinghua, Yang Haijun, Li Yong, Cai Zhenzhong, Yang Xianzhang, Xu Zhenping, Chen Cai, Sun Chunyan Major breakthrough in the Carboniferous-Permian in Well Qiatan 1 and exploration prospect in the piedmont southwestern Tarim Basin China Petroleum Exploration    2023, 28 (4): 34-45.   DOI: 10.3969/j.issn.1672-7703.2023.04.004 Abstract （235）   HTML    PDF （9925KB）（4）    Knowledge map    Save A major breakthrough has been made in the Carboniferous-Permian carbonate rocks in Well Qiatan 1 in Wuqia structural zone in the West Tianshan Thrust Belt, marking the discovery of a major replacement formation in the piedmont southwestern Tarim Basin. Combined with the regional geological data, studies on field outcrops, drilling, and seismic data, as well as the comprehensive analysis of laboratory experimental and test data in wells Qiatan 1 and Kuntan 1, hydrocarbon accumulation conditions in the Carboniferous-Permian in the piedmont southwestern Tarim Basin are re-recognized. The study results show that a “horseshoe-shaped” platform margin zone was developed in the Late Carboniferous-Early Permian in the piedmont southwestern Tarim Basin, and a favorable high-energy beach sedimentary facies zone was formed in belts, in which source rocks of bay lagoon facies were deposited in the Permian Qipan Formation, with a thickness of up to 500 m, type Ⅰ-Ⅱ organic matter, and high organic matter abundance. Jointly controlled by sedimentary facies and karstification, the fractured-vuggy type carbonate reservoirs were developed in the Late Carboniferous-Early Permian, forming a favorable reservoir and cap rock assemblage with the overlying thick mudstone in the Permian Qipan Formation. As a result, a new hydrocarbon accumulation pattern of “lower source rock and upper reservoir, hydrocarbon transport by fault and near-source accumulation” is established. The comprehensive analysis indicates that the fault anticline traps in the Carboniferous-Permian are distributed in rows and belts, which have the advantage of near-source hydrocarbon accumulation, and a number of favorable exploration targets such as wells Yetan 1 and Abei 1JS are optimally selected after evaluation, showing good exploration prospects, which are expected to be the major replacement field for large-scale gas exploration and discovery. Reference | Related Articles | Metrics

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Ding Feng, Wang Qiaohong, Mao Junli, Wang Shuo, Luo Ling Progress and thoughts on the reform of oil and gas mining rights management in the new era China Petroleum Exploration    2023, 28 (6): 1-7.   DOI: 10.3969/j.issn.1672-7703.2023.06.001 Abstract （230）   HTML    PDF （448KB）（8）    Knowledge map    Save In recent years, the Central Committee of the Communist Party and the State Council of China have successively issued a series of documents, including the reform of the oil and gas system, the reform of the equity fund system, and the reform of the mining rights transfer system, according to which the Ministry of Natural Resources has continuously promoted the reform of oil and gas mining rights management. The significant achievements after implementing reform measures in the new era are summarized, such as opening up the oil and gas exploration and production market, implementing mining rights competitive transfer, and deepening the reform of “optimizing the business environment”, as well as the challenges faced by the current reform work in the transfer, approval, and supervision of mining rights. Furthermore, some opinions and suggestions are provided, including expanding the source of oil and gas blocks, deepening the management mode, establishing a management system in accordance with geological understanding, and promoting comprehensive supervision, so as to further improve the mining right competitive transfer, build scientific mining rights relinquishment system, deepen the reform of “optimizing the business environment” and approval system, enhance the supervision of oil and gas mining rights, accelerate the formation of the new oil and gas exploration and production system dominated by state-owned business and supplemented by other economy sectors, and ensure national energy security. Reference | Related Articles | Metrics

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Zhou Lihong, Chen Changwei, Yang Fei, Cui Yu, Song Shunyao, Guan Quansheng, Zhou Fengchun Research and breakthrough of benefit shale oil development in Cangdong Sag, Bohai Bay Basin China Petroleum Exploration    2023, 28 (4): 24-33.   DOI: 10.3969/j.issn.1672-7703.2023.04.003 Abstract （211）   HTML    PDF （1841KB）（6）    Knowledge map    Save The large-scale and benefit development of shale oil in the second member of Kongdian Formation (Kong 2 member) in Cangdong Sag in Huanghua Depression face multiple challenges, such as evaluation and optimal selection of main production layers of medium-low mature shale oil, stereoscopic development and production of multiple vertical sweet spots, optimal and fast drilling and completion of horizontal section with a length of 2000 m in complex fault blocks, high-efficiency volumetric fracturing of laminated shale reservoir and high-efficiency lifting of shale oil with high viscosity and high wax content. Go through four stages of shale oil exploration, i.e., research, breakthrough in horizontal wells and pilot test of production capacity evaluation, 60% of the horizontal wells in production have a single well EUR of less than 2.0×10 4t, and the low single well oil rate has become a bottleneck problem restricting the benefit development of lacustrine shale oil. By comprehensively analyzing wireline logging, mud logging, fracturing parameters and production data of Kong 2 member shale oil in 47 production wells, the systematic research has been conducted on sweet spot evaluation and optimal selection of sealing box, well pattern deployment, geosteering while drilling, fracturing reconstruction, and production regime for the lacustrine shale oil in complex fault blocks, and three sweet spot layers (C1, C3 and C5) have been identified for benefit shale oil development in Guandong area, with an favorable area of 42-53.3 km 2 and the estimated Class Ⅰ resources of 1.54×10 8t. The pilot test of benefit shale oil development has been conducted on two 10 m-level sweet spot layers (C1③ and C3⑧) in Kong 2 member on No.5 platform in Cangdong Sag, in which the drilling difficulty of long horizontal section by water-based drilling fluids in complex fault blocks has been solved, the high-efficiency fracturing technology for laminated shale oil has been innovated, and permeability improvement, swelling energization and viscosity reduction of miscible fluids have been achieved of the laminated shale reservoir, with the tested single well peak oil output of 39.6-122.3t. As of June 22, 2023, the five pilot wells had been put into production for 174-201 days, and the cumulative oil output was 3.34×10 4t. The predicted cumulative oil output in the first year is 6.5×10 4t, and the average EUR of a single well is 4.11×10 4t, which indicate that the large-scale and benefit development mode of lacustrine shale oil has been established in complex fault blocks. Reference | Related Articles | Metrics

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Fang Rui, Jiang Yuqiang, Yang Changcheng, Wang Zhanlei, Sun Shasha, Zhu Xun, Li Shun, Gu Yifan, Zhou Yadong, Liu Dongxi, Luo Yao, Luo Yuzhuo Geological characteristics of shale oil in the Jurassic Lianggaoshan Formation in Sichuan Basin China Petroleum Exploration    2023, 28 (4): 66-78.   DOI: 10.3969/j.issn.1672-7703.2023.04.007 Abstract （204）   HTML    PDF （9399KB）（42）    Knowledge map    Save In recent years, major breakthroughs have been made in the exploration of the Jurassic lacustrine shale oil in Sichuan Basin, showing great exploration potential. In order to support the further deepening exploration, the field outcrop, logging, well drilling, coring and systematic core sample experimental data are combined to analyze the geochemical characteristics, rock brittleness, pore structure and oil and gas bearing properties of shale with various lithologic combinations in the Jurassic Lianggaoshan Formation, and identify the lithologic combination types of the dominant shale. The results indicate that the lithologic combination of shale interval in Lianggaoshan Formation is classified into three categories and five types, i.e., pure shale combination, shell type shale combination, and siltstone type shale combination; Among the five types of lithologic combinations, shale is in the mature stage, but there are differences in organic matter content, type, and brittle mineral content. The shale of pure shale combination has an average TOC of greater than 1%, Type Ⅱ 1 organic matter, and brittle mineral content of higher than 52%; The organic matter characteristics of the shale of the shell type shale combination are similar to those of the pure shale combination, but the content of brittle minerals is greater than 65%; The shale of the siltstone type shale combination has an average TOC of less than 1%, Type Ⅱ 2 organic matter type, and the brittle mineral content of greater than 65%. The main reservoir space of various combinations is composed of microfractures and inorganic pores (pore diameter of 10-500 nm). The siltstone type shale combination has a larger pore throat and better pore connectivity than the pure shale combination and shell type shale combination. The free hydrocarbon content of the pure shale combination is greater than 1 mg/g, showing good oil-bearing property. OSI of the pure shale combination and the siltstone type shale combination is greater than 100 mg/g of some samples, indicating good oil movability. The comprehensive analysis shows that pure shale combination and siltstone type shale combination are favorable lithologic combination for shale oil exploration. Benefiting from the good fracability, the siltstone type shale combination is the main sweet spot for shale oil exploration in Lianggaoshan Formation. Reference | Related Articles | Metrics

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Liu Yuxi, Bai Bin, Cao Jianzhi, Wang Rui, Zhu Rukai, Meng Siwei, Hou Xiulin Differences in geological characteristics and sweet spots evaluation of marine and continental shale oil: a comparative case study between Wolfcamp D shale oil in Permian Basin in north America and Gulong shale oil in Songliao Basin China Petroleum Exploration    2023, 28 (4): 55-65.   DOI: 10.3969/j.issn.1672-7703.2023.04.006 Abstract （197）   HTML    PDF （15150KB）（9）    Knowledge map    Save The global technical recoverable shale oil resources are 2512×10 8 t, and the cumulative crude oil output from shale series has reached up to 3.9×10 8 t in 2021, which has grown to be one of the major fields for global petroleum exploration and development. Based on the geological conditions and sedimentary characteristics, the “sweet spot” reservoir of continental shale oil in China is classified into three categories, i.e., interlayer type, mixed type and shale type, among which the interlayer type and mixed type shale oil are the main targets for global shale oil exploration and development. Recently, breakthrough has been achieved in the exploration of shale type shale oil. However, the sweet spot evaluation urgently needs to be deepened to provide a basis for achieving benefit shale oil development. Therefore, the geological characteristics between the Carboniferous Wolfcamp D marine shale oil in Permian Basin in north America and the Cretaceous Qingshankou Formation Gulong continental shale oil in China are compared, and the key indicators for sweet spot evaluation of shale type shale oil are discussed, so as to provide reference for the exploration and development of continental shale type shale oil in China. The comparative study indicates that the two sets of shales are dominated by felsic shale and clayey shale with high clay minerals and quartz contents, and show similar geological characteristics of formation overpressure, relatively light oil quality and high brittle mineral content; The reservoir space of Gulong shale oil is dominated by composite organic matter pores and bedding joints related to a large number of clay minerals, showing better connectivity than Wolfcamp D shale oil but slightly poorer organic carbon abundance. The geological sweet spot of Wolfcamp D shale includes organic-rich clayey shale and siliceous shale, while the engineering sweet spot is the organic-rich siliceous shale based on the fracturing results. Similarly, the geological sweet spot of Gulong continental shale oil includes organic-rich clayey shale and felsic shale by using evaluation indicator of retained hydrocarbon, and the engineering sweet spot is the silicic felsic shale. Reference | Related Articles | Metrics

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Chen Xingzhou, Guo Qiang, Zhang Bin, Han Hongwei, Sun Xinyu, Liu Yan, Du Xinjun Characteristics and exploration breakthrough of coal measure genetic biogas in Eastern Sag of Liaohe Depression China Petroleum Exploration    2024, 29 (1): 76-91.   DOI: 10.3969/j.issn.1672-7703.2024.01.006 Abstract （197）   HTML    PDF （1313KB）（1）    Knowledge map    Save The Eastern Sag of Liaohe Depression is one of the areas with the earliest biogas discoveries in China. The shallow biogas has not attracted much attention in the early exploration stage due to the good exploration results in the middle and deep formations, and there is a lack of understanding of source rocks and distribution law of shallow biogas. The geochemical characteristics of shallow gas (reservoir) in drilled wells are systematically analyzed, and a key index of carbon isotope is used to classify shallow gas (reservoir) in Eastern Sag into four types, including primary biogas, bio-transitional zone gas, transformed biogas and mixed type gas. Furthermore, the genesis of shallow gas is discussed, and it is indicated that the shallow biogas is dominated by coal measure genesis. The in-depth study supports to obtain geological understanding that the distribution of shallow biogas was distinctly controlled by coal measure strata, high-quality clastic rock reservoirs, two sets of regional cap rocks in the upper sub-member of the third member of Shahejie Formation (Es 3 1) and the first member of Shahejie Formation (Es 1), and the late formation of structures and late gas charging were conducive to the large-scale gas enrichment in shallow formations. Guided by the above understanding, high-yield gas wells and large-scale reserves have been discovered, opening up a new exploration field of coal measure genetic biogas in Liaohe Depression. Reference | Related Articles | Metrics

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Xie Guiqi, Lin Hai, Liu Shiduo, Liu Yong, Wan Youyu, Zhang Chengjuan, Li Yafeng, Cui Ronglong, Lei Fengyu, Sui Guojie, Deng Liben, Zhang Tao, Liu Huan, Liu Yunyi, Pu Yongxia Innovation and practice of geology and engineering integrated fracturing technology for shale oil in Yingxiongling area in the western Qaidam Basin China Petroleum Exploration    2023, 28 (4): 105-116.   DOI: 10.3969/j.issn.1672-7703.2023.04.010 Abstract （192）   HTML    PDF （2907KB）（2）    Knowledge map    Save The limy dolomite and shale are well developed in Lower Ganchaigou Formation shale series in Yingxiongling area in Qaidam Basin, and the favorable reservoirs of limy-dolomitic flat are superimposed and interbedded with high-quality source rocks, showing huge exploration and development potential of shale oil resources. However, there are some difficulties in reservoir reconstruction, such as high field stress, high stress difference, high-frequency sedimentary cycle, well-developed lamination in vertical direction, and strong reservoir heterogeneity. Therefore, it is urgent to develop a highly applicable and high-efficiency fracturing technology system to support the benefit exploration and high-efficiency development. By conducting geomechanical experiments, the law of shale rupture and fracture propagation is clarified, and the reservoir reconstruction idea of “controlling nearby fractures and propagating long fractures” is formulated; A new algorithm of 1D geomechanics and fracability is researched, and a 3D fine geomechanical model is established; The combination of model simulation optimization and data-driven optimization is applied to form a network fracturing technology template for vertical wells; By benchmarking the mainstream practices and key parameters of volume fracturing of continental shale oil in China, the concept of geology and engineering integration is implemented in cluster setting and fracturing parameters optimization, achieving the upgrade of volume fracturing technology with the core of “high-density cutting, extremely limiting flow perforation, large displacement, large scale, high-intensity and continuous slickwater sand addition, inverse composite ‘controlling nearby fractures and propagating long fractures’, and high quartz sand percentage”. A total of 37 fracturing operations were conducted in vertical wells, with an oil rate of 2.1-44.9 m 3/d, and the wells with commercial oil flows accounted for 97.2%; Another six fracturing operations were conducted in horizontal wells, with the maximum oil rate of 113.5 m 3/d, and the proven shale oil geological reserves of 5×10 8 t in the upper member of Lower Ganchaigou Formation. Reference | Related Articles | Metrics

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Zhang Yu, Zhao Peirong, Liu Shilin, Liu Chaoying, Cheng Zhe, Chen Qian, Chen Gang, Zhang Feiyan Main exploration progress and development strategy of Sinopec during the 14 th Five-Year Plan period China Petroleum Exploration    2024, 29 (1): 14-31.   DOI: 10.3969/j.issn.1672-7703.2024.01.002 Abstract （190）   HTML    PDF （18858KB）（0）    Knowledge map    Save A systematic review is conducted on the high-quality exploration activities, theoretical and technological progress, and exploration achievements of Sinopec during the 14 th Five-Year Plan period, and a development strategy is proposed for the future petroleum exploration. Since the 14 th Five-Year Plan period, Sinopec has strengthened its confidence in resource development and vigorously promoted high-quality exploration practices, which support to make significant exploration achievements in fields such as deep carbonate rocks, continental shale oil, deep shale gas, clastic rocks in western regions, subtle oil and gas reservoirs in mature exploration areas, and deep CBM in Tarim, Sichuan, Bohai Bay, Junggar, and Ordos basins, solidifying reserve basis for stable oil output growth and rapid gas output growth. In addition, significant progress has been made in the development and improvement of deep strike-slip fault-controlled fracture-cavity type hydrocarbon accumulation theory, the innovative shale oil reservoir formation, hydrocarbon accumulation and enrichment theory, and the deep understanding of “dual enrichment” of marine shale gas and differential enrichment mechanisms of oil and gas reservoirs in tight clastic rocks. Furthermore, the key exploration and engineering technologies for targets with complex geological and reservoir structural conditions, represented by seismic exploration, well drilling and completion in deep to ultra-deep formations, wireline logging, mud logging and well testing in ultra-deep formation, and horizontal well fracturing, have been researched and developed. Looking ahead, Sinopec has a solid resource foundation in its exploration areas for achieving steady oil output and rapid increase in gas production. The exploration work will focus on three core responsibilities of securing and expanding mining rights areas, achieving exploration breakthroughs, and increasing reserves and resources on a large scale. Guided by deep earth engineering, shale oil and gas demonstration projects, benefit development of tight clastic rock oil and gas reservoirs, and coordination of conventional and unconventional resources, efforts will be strengthened to accelerate the strategic breakthroughs, and establish large-scale reserve increase bases, so as to further consolidate resource foundation for the sustainable development of the upstream. Reference | Related Articles | Metrics

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Han Yaqin, Mao Junli, Si Xiang, Wen Yaping, Yao Xing Reform and practice of integrated oil and gas exploration and production system in China China Petroleum Exploration    2023, 28 (6): 8-14.   DOI: 10.3969/j.issn.1672-7703.2023.06.002 Abstract （183）   HTML    PDF （420KB）（3）    Knowledge map    Save In order to promote the orderly connection between oil and gas exploration rights and mining rights, and to address long-standing issues, the Ministry of Natural Resources issued the “Opinions of the  Ministry of Natural Resources on several issues concerning promoting the reform of mineral resources management (for trial implementation)” in December 2019, in which the concept of the integrated oil and gas exploration and production was first proposed. By considering the characteristics of oil and gas resources exploration and development, the integrated oil and gas exploration and production system enables to preliminarily address the legality of acquiring oil and gas during the exploration stage, which aligns with the laws governing oil and gas exploration and development, and helps stimulate vitality and promote the upstream oil and gas exploration and development. However, there are still multiple issues to be clarified. Based on a review of data and information of exploitable blocks, and supported by investigation and research, the implementation status of the integrated oil and gas exploration and production system is summarized and analyzed, which indicates that there are problems at the operational level, such as the need for further standardization in the management, a lack of alignment with the current system, and an inadequate enforcement of supervisory responsibilities. In view of this, it is proposed to standardize the integrated system from two aspects of the reporting period of the exploitable resources and the issuance of receipts for exploitable oil and gas resources. The connection between the integrated system and relevant administrative licensing systems should be improved at two levels of mining rights approval and two-certificate management. The supervisory system for the integrated system should be further improved and the revision of relevant legal and regulatory provisions should be accelerated. Furthermore, by combing with the current development situation in the oil and gas industry, the concept of a unified management of the integrated oil and gas exploration and production, namely the “one-certificate approach”, is put forward. Reference | Related Articles | Metrics

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Li Shixiang, Guo Qiheng, Pan Songqi, Zhou Xinping, Guo Ruiliang Influence of intrasource micro-migration of hydrocarbons on the differential enrichment of laminated type shale oil: a case study of the third sub-member of the seventh member of the Triassic Yanchang Formation in Ordos Basin China Petroleum Exploration    2023, 28 (4): 46-54.   DOI: 10.3969/j.issn.1672-7703.2023.04.005 Abstract （182）   HTML    PDF （8261KB）（11）    Knowledge map    Save Influenced by multi type and high density laminae of continental shale, the differential intrasource micro-migration of hydrocarbons is an important factor controlling the oil-bearing property and mobility of the laminated shale with various lithofacies. By taking the systematic shale coring sections in 10 wells in Ordos Basin as the research object and using laboratory experimental results such as XRD, thin section observation, SEM, nitrogen absorption, laser scanning confocal, geochemical test, as well as wireline logging and well testing results,the hydrocarbon micro-migration inside shale section in the third sub-member of the seventh member of the Triassic Yanchang Formation (referred to as Chang 7 3 sub-member) and the mechanism are analyzed. The study results show that the micro-millimeter scale migration generally occurred of crude oil generated by organic-rich laminated shale. Among them, hydrocarbon generation pressurization provided forces for micro-migration; The frequently developed brittle laminae provided a large amount of reservoir space for the micro migrated hydrocarbon; The hydrocarbon generation pressurization fractures, foliation fractures, and micro fractures provided pathways for micro-migration; The different mineral compositions of the laminae resulted in hydrocarbon differentiation. The combination type of laminae and differential micro-migration mechanism determine that the felsic laminated shale and tuffaceous laminated shale have relatively good oil-bearing property and mobility, which are the main lithofacies types for risk exploration of medium-high maturity laminated type shale oil. The commercial oil flow of more than 10 t/d was obtained in pilot test of Chang 7 3 sub-member shale in seven vertical wells, confirming that shale section in Chang7 3 sub member has good oil-bearing property, and there is a high potential of production increase by horizontal well development, which is expected to be a replacement field for reserve and production increase of shale oil in Ordos Basin. Reference | Related Articles | Metrics

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Zhi Dongming, Li Jianzhong, Yang Fan, Kang Jilun, Zhang Wei, Ma Qiang, Tao Linben Geological characteristics and exploration and development practice of the Permian full oil and gas system in Jimsar Sag, Junggar Basin China Petroleum Exploration    2023, 28 (4): 14-23.   DOI: 10.3969/j.issn.1672-7703.2023.04.002 Abstract （182）   HTML    PDF （12410KB）（9）    Knowledge map    Save Based on the study of source rock, sediment source system, tectonic evolution and dynamic matching relationship between hydrocarbon source and reservoir, the Permian oil and gas bearing system in Jimsar Sag is analyzed in detail. The study results indicate that the Permian in Jimsar Sag has favorable geological conditions for forming full oil and gas system. On the plane, shale oil, tight oil, conventional glutenite oil reservoirs are distributed in sequence from the central to the marginal sag, and tight oil, shale oil, conventional glutenite oil reservoirs are distributed upward around the high-quality source rock in Lucaogou Formation, showing the overall hydrocarbon accumulation characteristics of “full oil and gas system”. Guided by this understanding, breakthroughs have been made in the exploration of three types of oil reservoirs, basically forming a pattern of oil bearing in the whole sag and orderly co-occurrence and superposition of multi-layer and multi type oil reservoirs. By applying the large platform and multi-layer stereoscopic development mode, the exploration idea and technology for maximizing the benefit resource utilization are gradually mature in practice. The detailed analysis of geological characteristics, hydrocarbon accumulation pattern, and exploration and development practice of the Permian full oil and gas system in Jimsar Sag is of great significance for enriching the exploration theory of the full oil and gas system and guiding the exploration and development in similar oil rich sags. Reference | Related Articles | Metrics

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Zhang Yunyi Pilot test of cross-layer fracturing in horizontal shale oil well: a case study of Hua H100 platform in Qingcheng Oilfield China Petroleum Exploration    2023, 28 (4): 92-104.   DOI: 10.3969/j.issn.1672-7703.2023.04.009 Abstract （178）   HTML    PDF （3764KB）（4）    Knowledge map    Save A total of 31 horizontal wells have been drilled on Hua H100 platform in Qingcheng Oilfield in Ordos Basin. For the first time, the cross-layer fracturing is tested in four horizontal wells on this platform with low drilling rate of reservoir. Meanwhile, by applying tracer monitoring technology, the engineering feasibility of penetrating mudstone and communicating the adjacent sandstone reservoirs and the effectiveness of flow pathway after fracturing are analyzed, and the production contribution of the cross-layer fracturing stage is evaluated. The pilot test results show that when the distance between the horizontal well trajectory in the non-reservoir interval and the sandstone reservoir is less than 3 m and the clay content is lower than 40%, the cross-layer fracturing engineering is feasible. A total of 14 stages have been tested and good results have been achieved in 12 stages, with a success rate of 85.7%, confirming the feasibility of cross-layer fracturing operation. The tracer detection and interpretation results show that continuous water flowback has been monitored in cross-layer fracturing stages, which indicate that an effective flow pathway has been formed after soaking the well. The varying amounts of oil production in various cross-layer fracturing stages also demonstrate that the sandstone reservoirs have been communicated by cross-layer fractures, with a definite production contribution. Compared with another four offset wells with drilling rate of higher than 80% on the same platform, the cumulative oil production of cross-layer fracturing wells is above the average level. The successful pilot test of Hua H100 platform proves that the cross-layer fracturing is an effective engineering means to increase single well production of horizontal wells with low drilling rate of reservoir. Reference | Related Articles | Metrics

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Zhang Ruifeng, Chen Shuguang, Feng Guangye, Shi Yulei, Hu Yanxu, Sun Ruina, Wan Zhaofei, Wu Han, Tian Sisi, Zhang Yufei, Wang Guanmei, Zhou Ranran, Luo Yucai, Wang Xiaochao, Zhang Ximeng Formation conditions and exploration prospects of ultra-deep oil and gas reservoirs in Paleogene Linhe Formation in northern Linhe Depression China Petroleum Exploration    2024, 29 (1): 119-129.   DOI: 10.3969/j.issn.1672-7703.2024.01.009 Abstract （176）   HTML    PDF （2330KB）（1）    Knowledge map    Save In recent years, a major discovery of oil and gas exploration in ultra-deep clastic rocks has been achieved in Linhe Depression of Hetao Basin by increasing the geological understanding of late oil and gas accumulation in deep ultra-deep clastic rocks.Based on the thermal simulation of Paleogene source rocks, drilling and logging data and analysis of reservoir formation and accumulation evolution, three important geological understandings are mainly formed. （1）High-quality source rocks rich in resinite ( terrestrial ) and algae ( aquatic ) are developed in the Paleogene in the northern part of Linhe Depression. The source rocks begin to generate and expel a large amount of hydrocarbons in the low evolution stage, which has the characteristics of high hydrocarbon generation intensity and wide hydrocarbon generation window. The ultra-deep thermal evolution degree of the trough area is relatively high, and the potential of oil and gas resources is large. （2）The braided river delta deposits are developed in the shallow slope of the far source water, and the sand bodies are widely distributed. Affected by weak diagenesis such as low geothermal temperature, late deep burial, high quartz content, weak compaction and weak cementation, a new mechanism of reservoir formation and storage is put forward, which is dominated by weak diagenesis and pore preservation, and superimposed by epigenetic ultra-high pressure transformation and fracture expansion. The reservoir has good physical properties and greatly expands the space of ultra-deep oil and gas exploration. （3）A new understanding of conventional oil and gas accumulation is put forward, which includes early filling in hydrocarbon generation period, continuous subsidence, deep buried thermal evolution, accelerated hydrocarbon generation and expulsion, continuous filling to form supersaturated and ultra-high pressure oil and gas reservoirs, and natural fracturing of reservoir-source interaction bodies by ultra-high pressure, forming fracture-pore connectivity, source-reservoir convergence and continuous large-area distribution, which effectively improves the exploration potential of ultra-deep conventional oil and gas reservoirs.The above studies show that the ultra-deep oil and gas accumulation conditions of the Paleogene Linhe Formation in the northern part of the Linhe Depression are superior. Combined with the large area of favorable exploration areas, it shows a good exploration prospect. At the same time, it further enriches the theoretical understanding of the late oil and gas accumulation of ultra-deep clastic rocks. It has important guiding significance for the exploration of similar basins, especially the ultra-deep source of 10,000 meters. Reference | Related Articles | Metrics

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Xu Changgui, Zhu Guanghui, Ji Hongquan, Zhu Yanhe, Sun Qiang Exploration progress and reserve increase strategy of onshore natural gas of CNOOC China Petroleum Exploration    2024, 29 (1): 32-46.   DOI: 10.3969/j.issn.1672-7703.2024.01.003 Abstract （174）   HTML    PDF （3098KB）（0）    Knowledge map    Save In order to achieve the rapid development of natural gas industry and increase gas production, CNOOC has gradually increased exploration investment in mining rights areas in Ordos Basin and Qinshui Basin, in which there are multiple types of natural gas including tight gas, CBM, and conventional gas, with gas resources of up to 3×10 12m 3 in the two basins and proven gas geological reserves of 7500×10 8m 3 in high-abundance and structurally simple zones. Based on a comprehensive analysis of resource potential and quality, gas accumulation conditions, and exploration technology, CNOOC has proposed a development strategy of increasing onshore natural gas reserves with a level of trillion cubic meters. The company has clarified the guiding ideology of simultaneous exploration of tight gas and CBM and stereoscopic exploration of multi type gas resources, and determined the deployment strategy of accelerating the exploration of deep CBM and tight gas in the eastern part of Ordos Basin and rapidly promoting the exploration of middle and shallow CBM in Qinshui Basin. Furthermore, the comprehensive analysis of exploration fields, gas accumulation and enrichment laws, and exploration technology research directions enables to clarify the key exploration orientations in the near future. The eastern Ordos Basin is characterized by orderly co-occurrence of full oil and gas system in coal measure strata. As a result, it is necessary to conduct exploration in the full gas accumulation system in coal measure strata, consolidate the material basis for increasing reserves and production, focus on tight gas and deep coalbed methane, research on CBM in thin cool seams, Ordovician conventional natural gas, and bauxite rock gas, and promote the simultaneous exploration and replacement of multi type gas resources by applying exploration and development integration and geology and engineering integration, so as to achieve the exploration and development of full gas accumulation system. In the northern and southern parts of Qinshui Basin, it is necessary to promote the volume fracturing of horizontal wells and production technology tests for middle and shallow CBM and popularize its application, and form complementary economic and effective development with thin CBM, so as to promote the overall increase in CBM reserves and production in Qinshui Basin. The exploration activities in the above key areas will ensure the reserve increase and healthy and stable development of large onshore gas region of CNOOC with a level of trillion cubic meters. Reference | Related Articles | Metrics

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Zhou Lihong, He Haiqing, Chen Changwei, Li Changhai, Shi Qianru, Dong Yueqi, Cui Yu, Zhang Jiaoyang, Zhu Huahui, Zhang Mingzhen Exploration breakthrough and enlightenment of Dongying Formation in Well Haitan 1 in the deep subsag area in Binhai Slope, Qikou Sag China Petroleum Exploration    2023, 28 (6): 78-89.   DOI: 10.3969/j.issn.1672-7703.2023.06.010 Abstract （165）   HTML    PDF （10643KB）（2）    Knowledge map    Save In order to achieve the “oil exploration in the deep subsag” in Qikou Sag and find a new field for increasing reserves and production, Well Haitan 1 has been deployed in the deep subsag in Binhai Slope in Qikou Sag and a major breakthrough has been made. Based on the drilling results, the detailed analysis on the control mechanism of sand body development, reservoir characteristics, hydrocarbon generation conditions and hydrocarbon accumulation pattern in Dongying Formation in the deep subsag area in Binhai Slope is conducted. The study results show that: (1) The gravity flow sand body supplied by the north Yanshan provenance was developed in the third member of Dongying Formation (Dong 3 member) in the deep subsag area in Binhai Slope, showing good reservoir physical property; (2) The self-generation and self-storage oil and gas bearing system was discovered in Dong 3 member for the first time, breaking through the previous understanding of hydrocarbon migration through faults and “lower source rock and upper reservoir”; (3) The hydrocarbon accumulation pattern of “long distance sand transportation, near source hydrocarbon charging, coupling of source rock and reservoir, and contiguous oil bearing” in Dong 3 member in the deep subsag area has been established; (4) In addition, shale oil in Dong 3 member in the deep subsag area shows huge resource potential. The successful drilling of Well Haitan 1 supports to find a new field in the eastern mature oilfields and provides favorable reference for “oil exploration in the deep subsag”. Reference | Related Articles | Metrics

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Cheng Jian, Zhou Xiaojin, Wang Ping, Cao Qinggu, Yu Qixiang, Li Fengli Study on the favorable expansion orientation of mining rights blank zones in the peripheral Ordos Basin and surrounding basins China Petroleum Exploration    2023, 28 (6): 90-104.   DOI: 10.3969/j.issn.1672-7703.2023.06.011 Abstract （161）   HTML    PDF （1686KB）（1）    Knowledge map    Save Ordos Basin and its surrounding basins such as Hetao, Yinchuan, Liupanshan, and Weihe are characterized by coexistence of multiple types of resources in one basin, and they have prominent resource advantages in China’s large onshore basins. However, the degree of resource exploration is low, and there are a large number of mining rights blank zones, which are the major targets for favorable area screening and mining rights and resource space expansion of oil companies in the future. After analyzing new discoveries, summarizing new geological understanding, and correlating hydrocarbon accumulation conditions and resource potential in mining rights blank zones with the adjacent exploration areas, the study results indicate that: (1) The Upper Paleozoic coal seams and dark mudstone have a large thickness and high hydrocarbon generation intensity, and the structural settings are stable in Wanzhen area in the middle section of the eastern basin margin, showing exploration potential of tight gas and deep coalbed methane in the Upper Paleozoic. (2) The Carboniferous-Permian coal seams have a large residual thickness and moderate burial depth in Hangjinqi and Dongsheng areas in the northern basin margin, which are favorable areas for coalbed methane and coal chemical industry. (3) The continental shelf facies shale was developed in the Middle-Late Ordovician in the western basin margin, with a wide area and good hydrocarbon source conditions. Multiple platform marginal reef or fractured type oil and gas reservoirs mainly supplied by source rock in Ulalik Formation (Pingliang Formation) have been discovered. Based on the study of preservation conditions, it is believed that Shigouyi syncline and Taole fault terrace zone in the western basin margin are favorable areas for discovering the Lower Paleozoic carbonate and marine shale oil and gas reservoirs. (4) Among the surrounding basins, Linhe Depression in Hetao Basin is the most favorable exploration area. Two sets of high-quality source rocks were deposited in the Lower Cretaceous Guyang Formation and the Oligocene Linhe Formation in most areas in Linhe Depression, with strong hydrocarbon generation potential. Surrounding the main hydrocarbon generation Naoxi sub-sag, multiple sets of deep strike slip faults were developed in the southeast fault terrace zone, showing good connection to source rock. The high-efficiency hydrocarbon accumulation mode has been confirmed. (5) The Triassic and Jurassic source rocks were developed in Liupanshan Basin with good hydrocarbon generation conditions similar to those in Ordos Basin. The deep formations in the basin are worthy of further exploration. (6) The saline lake facies source rock in Qingshuiying Formation and oil-bearing structures were proved by wells in Yinchuan Basin. The structural belt in the peripheral mature hydrocarbon generating sag in the northern basin is a favorable orientation for exploration. (7) Weihe Basin and Huhe Depression in Hetao Basin are located in economically developed areas, and abundant shows of water soluble helium gas, geothermal energy, and biogenic gas have been penetrated by drilling activities. The oil and gas co associated resources in these areas are complementary to conventional oil and gas exploration, and the in-situ transformation and comprehensive utilization of resources can be achieved. After study, it is suggested that 10 new mining rights should be established and planned in favorable areas such as Wanzhen, Heyang, Hangjinqi-Zhungeerqi, Taole fault terrace zone, and Shigouyi syncline in Ordos Basin, Haiyuan-Guyuan Sag and the piedmont nappe structural belt in Liupanshan Basin, the southeast fault terrace zone in Linhe Depression and Huhe Depression in Hetao Basin, as well as Pingluo Sag in Yinchuan Basin. In addition, it is recommended that relevant companies should strengthen the pre evaluation and pre research in mining rights blank zones, and actively evaluate and demonstrate oil and gas potential in new blocks, so as to lay the foundation for maintaining the dynamic balance between farm-in and farm-out of mining rights and ensuring survival space of oil companies. Reference | Related Articles | Metrics

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Yang Yang, Lai Yating, Zhang Xinyi, Gong Xiaoke, Han Jiangchen Characteristics, development risks and effective producing countermeasures of water-bearing tight gas reservoir: a case study of water-bearing area in Sulige Gasfield China Petroleum Exploration    2023, 28 (6): 121-133.   DOI: 10.3969/j.issn.1672-7703.2023.06.014 Abstract （153）   HTML    PDF （1376KB）（4）    Knowledge map    Save Sulige Gasfield is an example of successful tight gas development in China. However, with the progress of gas field development,the problem of water production from gas reservoir is gradually prominent. The water-bearing tight gas reservoirs are developed in the western,northeastern and southwestern parts of Sulige Gasfield, with proven gas reserves of trillions of cubic meters, and the large-scale beneficial gas development is facing great challenges. The analysis shows that the produced formation water is dominated by CaCl 2 type and metamorphic ancient sedimentary water, which is divided into three types of free water, capillary water and bound water. The formation and distribution of water-bearing tight gas reservoirs were affected by several factors, such as gas generation intensity, micro structures, reservoir heterogeneity,and fault system, which were generally developed in areas with low gas generation intensity, while gas enrichment areas were located in local positive micro structures. The evaluation results indicate that are multiple risks in the development of water-bearing tight gas reservoirs,including formation water intrusion, low gas rate of single well, low economic returns, high production cost, and HSE and management. As a result, a series of researches should be strengthened, such as sweet spot area prediction in micro structures, gas/water layer logging interpretation and identification, fine description of effective reservoir space, mixed development well pattern of vertical/deviated well + horizontal well, production measures optimization and low-cost production technology, centralized treatment of produced water and prevention of safety and environmental protection issues, and whole-process water intrusion prevention and control and risk management, so as to realize the successful development of water-bearing tight gas reservoirs. Reference | Related Articles | Metrics

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Wang Yuan, Yang Henglin, Huang Haoyong, Fu Li, Chen Gang, Zhang Heng, Wang Zixin, Guo Kaijie Geomechanical study of deep shale gas and application in Luzhou block, Sichuan Basin China Petroleum Exploration    2023, 28 (5): 68-83.   DOI: 10.3969/j.issn.1672-7703.2023.05.006 Abstract （152）   HTML    PDF （6459KB）（4）    Knowledge map    Save The deep shale gas reservoir (3500-5000m) in the Silurian Longmaxi Formation in Luzhou block in Sichuan Basin is an important replacement field for shale gas development in China. However, the geomechanical properties of reservoir rock and variation in in-situ stress lead to difficulties in the development process, such as the long drilling cycle and large difference in gas rate of a single well. The geomechanical study enables to deepen the understanding of in-situ stress field in the block and provides basis for optimizing well location placement, drilling engineering and fracturing design of horizontal shale gas wells. The acoustic logging, diagnostic fracture injection testing (DFIT), imaging logging, and laboratory stress measurement data are combined to construct a high-precision geomechanical model in Petrel software, which supports to identify the reservoir geomechanical property in the study area, and the application of geomechanical study results in engineering is discussed. The results show that Young’s modulus gradually increases and Poisson’s ratio decreases with the increasing burial depth in Luzhou block. The shale reservoir in Longmaxi Formation is characterized by abnormally high pressure, with pore pressure gradient ranging in 16.7-21.7 kPa/m. The strike-slip type stress regime is dominant in Luzhou block, with an overlying rock pressure gradient of 25.5 kPa/m, a minimum horizontal principal stress gradient ranging in 18.8-24.5 kPa/m, and the average ratio of the maximum horizontal principal stress to the minimum horizontal principal stress of 1.165, and the reservoir horizontal principal stress increases with the increase of Young’s modulus and pore pressure. The geomechanical study results are used to guide the well location placement, optimization of drilling fluid density in drilling engineering, and optimization of fracturing stages and clusters and engineering parameters in fracturing design. For example, the drilling fluid density was optimized to 1.85 g/cm 3 in Well Y65-X, achieving “one trip drilling” of the deviated-horizontal section and a 67% reduction in drilling cycle compared to adjacent wells; The fine fracturing stages and clusters and engineering parameters were optimized for Well Y2-X, and a gas flow rate of 50.69×10 4 m 3/d was tested. The study concludes that the high-precision geomechanical model and achievements enable to effectively improve the drilling operation efficiency and gas flow rate of a single well, and serve for the benefit development. Reference | Related Articles | Metrics

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Feng Yongtai, Liu Chaoying, Cheng Zhe, Fu Dayong Measures to the reform of national oil and gas system and innovative practice of Sinopec China Petroleum Exploration    2023, 28 (6): 47-54.   DOI: 10.3969/j.issn.1672-7703.2023.06.006 Abstract （151）   HTML    PDF （498KB）（1）    Knowledge map    Save In order to further improve the national oil and gas mining rights management system, new measures and innovative practices in line with the reform of national oil and gas system since the restructuring of Sinopec are systematically summarized. Furthermore, problems in the management of oil and gas mining rights are analyzed and the targeted suggestions are proposed. By analyzing the changes in exploration area of Sinopec in three stages, i.e., “application first, registration according to law”, “reduction of exploration rights area in proportion to insufficient investment”, and “mandatory reduction speculated in Document No. 7”, the innovative practices are summarized, including strengthening the nationwide strategic selection of exploration areas and actively acquiring new mining rights, strengthening the linkage between mining rights and reserves and internal circulation of mining rights responding to new situations, and establishing an evaluation system for acquiring new mining rights at reasonable prices. These measures have ensured a virtuous cycle of Sinopec’s petroleum exploration and development work and ushered in a new level of proven oil reserves of 2×10 8 t in 2022. However, in mining rights management, the competitive transfer and mandatory reduction policy upon expiration of exploration rights result in the rapid reduction of exploration rights area of petroleum enterprises. A large number of mining rights blocks have been acquired by weaker enterprises, which are challenging to achieve substantial exploration progress and delay the exploration and development of mining rights blocks. As a result, it is recommended to increase the proportion of technical bidding documents in the competitive transfer process to ensure that petroleum enterprises with strong strength and responsibility obtain sufficient exploration area. Reference | Related Articles | Metrics

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Sun Jianbo, Shi Bin, Guo Chao, Gao Chao, Bai Fenfei, Liu Gang, Yin Jintao, Xu Jie Characteristics of shale oil reservoir and exploration prospects in the third sub-member of the seventh member of the Triassic Yanchang Formation in Fuxian area, Ordos Basin China Petroleum Exploration    2023, 28 (4): 79-91.   DOI: 10.3969/j.issn.1672-7703.2023.04.008 Abstract （151）   HTML    PDF （6797KB）（5）    Knowledge map    Save During the deposition period of the third sub-member of the seventh member of the Triassic Yanchang Formation (Chang 7 3 sub-member), Fuxian area was located in the depo-center of the eastern lake basin, showing abundant shale oil resources and good exploration prospects. However, few studies have been conducted on shale oil reservoir characteristics, and there is a lack of the study on reservoir space characteristics and oil-bearing property, which restrict shale oil exploration and deployment practice. By using core observation, whole rock mineral XRD analysis, chloroform extraction, NMR, organic carbon abundance and porosity test data, the petrological and mineralogical characteristics, reservoir space, pore structure and oil and gas bearing property are analyzed in Fuxian area, which indicates that three rock categories are observed in Chang 7 3 sub-member, such as shale, silty-fine sandstone and tuff. Based on the development degree of lamina, the shale category is subdivided into four rock types. The main mineral composition of shale section includes quartz, feldspar, carbonate and clay minerals, as well as a small amount of pyrite. The reservoir is dominated by four types of pores, i.e., intergranular pore, intragranular pore, organic pore and microfracture. The meso-macropores are relatively developed in silty-fine sandstone, and the NMR T 2 spectrum is characterized by multi-peak and left-biased single-peak types. The micropores are relatively developed in black shale, with relatively few macropores, and the NMR T 2 spectrum is mainly multi-peak and right-biased single-peak types. The silty-fine sandstone with good oil-bearing property and high oil saturation index is the optimal shale oil reservoir in Chang 7 3 sub-member, followed by the laminated shale. The comprehensive study indicates that both silty-fine sandstone and shale targets have certain exploration potential, which are potential fields for increasing reserves and production in the future. Reference | Related Articles | Metrics

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Tian Hongzhao, Yuan Xiufa, Li Yunyun, Wang Yuzhu, Luo Jun, Cao Xiaoli, Zhao Guoying, Xu Chuanlong, Wu Zexin, Zhu Huijuan Optimization design and practice of CO 2 foam fracturing with geology and engineering integration: a case study of Su X block in Sulige Gasfield China Petroleum Exploration    2023, 28 (5): 126-134.   DOI: 10.3969/j.issn.1672-7703.2023.05.011 Abstract （147）   HTML    PDF （1727KB）（7）    Knowledge map    Save CO 2 foam fracturing is an effective measure to improve the development result of tight sandstone gas reservoir. The central part of Su X block in Sulige Gasfield is a major replacement area for stable gas production in the near future. Compared with the main production area in the northern part, it is characterized by poor reservoir continuity and physical properties, high saturation of movable water, leading to severe water lock damage of gas wells when using conventional water-based fracturing, and increasing difficulty in fracturing fluid flowback. By taking Well Su X-A3 as an example, the concept of geology and engineering integrated CO 2 foam fracturing is innovatively practiced.Firstly, the integration of geological modeling and numerical simulation is applied to analyze the production characteristic parameters such as reservoir physical properties, gas-bearing property and movable water distribution, so as to optimally select well location and perforation interval to avoid formation water damage; Secondly, the geology and fracturing integration is applied to analyze the matching between reservoir physical properties and fracturing technology, so as to optimize the fracturing fluid system, fracturing size and pumping program; Finally, by using the flowback, well test, and gas production data, the evaluation and correction integration is applied to assess the fracturing results and technological adaptability, correct the pre-fracturing geological model, and complete the closed loop of geology and engineering integration technology. The study results show that the application of the geology and engineering integration in the optimization design of CO 2 foam fracturing enables to more comprehensively and accurately understand the reservoir quality and production performance, improve the pertinence of CO 2 foam fracturing design, and provide guarantee for a better result by using CO 2 foam fracturing. Field practice shows that this method is more in line with the practical needs than the previous conventional water-based fracturing design. Reference | Related Articles | Metrics

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Wang Qinghua, Min Lei, Zhou Peng, Luo Juncheng, Yang Xianzhang, Xu Zhenping, Zhang Xueqi, Cui Deyu Concept transformation and management upgrade of mining rights protection in Tarim Oilfield China Petroleum Exploration    2023, 28 (6): 55-63.   DOI: 10.3969/j.issn.1672-7703.2023.06.007 Abstract （145）   HTML    PDF （775KB）（1）    Knowledge map    Save Mining rights are the “lifeline” of oil and gas field enterprises. With the continuous efforts in mining rights management, more stringent block withdrawal mechanism, and the implementation of competitive transfer by the government, the state-owned oil and gas enterprises are facing greater competitive and reform pressure. As a result, the deep understanding of the reform trend of oil and gas mining rights management and a detailed analysis of the existing problems and challenges are of great significance for reform and management, leveraging their own advantages, and achieving high-quality development of state-owned oil and gas enterprises. On the basis of systematically summarizing the exploration history and the evolution of mining rights, the challenges and situation faced by mining rights management are analyzed, and the practice of initiatively adapting to mining rights reform and innovating management of Tarim Oilfield is demonstrated in detail. By using measures such as establishing regulations and systems, linking mining rights with exploration and development activities, finely conducting basin evaluation, and enhancing information construction, the plans for the renewal/relinquishment of mining rights upon expiration have been prepared and the strategic research on competitive transfer of mining rights has been conducted, which support to effectively stimulate stock mining rights, actively acquire new mining rights, and form a new system of mining rights management which is characterized by “evidence-based farm in, orderly withdrawal, and standardized management”.Finally, based on the practice of mining rights management, three suggestions are put forward, including encouraging exploration and discovery of the mining rights renewal policy, policy support in areas with proven reserves concentrated, and improving the coordination and management of mining rights and land use policy, so as to better support the development of domestic oil and gas business and ensure national energy security. Reference | Related Articles | Metrics

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Liu Ce, Liang Kun, Zhang Ying, Wu Peihong, Ran Qigui, Kong Fanzhi, Yu Huaqi, Xing Ya, Kong Hua Management measures and evaluation system design of PetroChina for the reduction of exploration rights area under the new situation China Petroleum Exploration    2023, 28 (6): 37-46.   DOI: 10.3969/j.issn.1672-7703.2023.06.005 Abstract （142）   HTML    PDF （687KB）（2）    Knowledge map    Save According to the requirements of deepening the reform of oil and gas system, a more stringent exploration rights withdrawal mechanism has been implemented in China since May 2020, which changed from a reduction/withdrawal according to the proportion of insufficient investment to a compulsory withdrawal/reduction upon expiration of exploration rights. In order to adapt to the new policy, PetroChina timely adjusted its management philosophy and actively introduced new measures to achieve the renewal and orderly reduction of the first-round exploration rights upon expiration. Based on the practice of orderly reduction/withdrawal of exploration rights in more than three years, the main management measures of PetroChina, the thoughts on the optimization design of the national exploration rights reduction/withdrawal system, and the design thoughts of the evaluation system supporting the decision-making of exploration rights reduction/withdrawal management are mainly discussed. In terms of the management of the exploration rights area withdrawal/reduction, two main measures are proposed: (1) Implement multi-business linkage and integration mechanism to accelerate the pace of pursuing exploration and discovery before the expiration of exploration rights; (2) Strengthen the organization, management and review of the preparation of reduction/withdrawal plans to fully ensure a solid foundation of high-quality resources for the exploration and development. In addition, the direction for further optimization of the national exploration rights withdrawal/reduction system is analyzed and two suggestions are proposed as follows: (1) Further increase the targeted incentives for exploration rights blocks obtaining new discoveries, and significantly reduce or even exempt the area reduction in these blocks; (2) Under the specified circumstances, provide certain institutional preferential policies to market entities undertaking the duty of national energy supply guarantee. In view of the exploration rights evaluation system, it is innovatively proposed that the design of evaluation system of exploration rights blocks should start from five aspects of recoverability, resource conditions, hydrocarbon accumulation conditions, economy, and other conditions to comprehensively and finely understand the value of exploration rights blocks, so as to support the subsequent decision-making of exploration rights reduction/withdrawal management of enterprises and provide certain reference for the government to analyze and determine the value of exploration rights blocks. Reference | Related Articles | Metrics

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He Xiao, Liang Feng, Li Hai, Zheng Majia, Zhao Qun, Liu Yong, Liu Wenping Breakthrough and enrichment mode of marine shale gas in the Lower Cambrian Qiongzhusi Formation in high-yield wells in Sichuan Basin China Petroleum Exploration    2024, 29 (1): 142-155.   DOI: 10.3969/j.issn.1672-7703.2024.01.011 Abstract （138）   HTML    PDF （10131KB）（1）    Knowledge map    Save Small progress has been made in the exploration and development of shale gas in the Lower Cambrian Qiongzhusi Formation over the years. The high-yield gas flow in Well Zi 201 has greatly increased confidence in the large-scale and commercial development of shale gas in Qiongzhusi Formation. The different enrichment laws in various areas and layers and the optimal selection of favorable areas are the primary problems to be solved for shale gas development. Based on the analysis of paleontology, sedimentary facies, and reservoirs in 57 wells in Sichuan Basin, the theoretical basis for the deployment of Well Zi 201 and enrichment conditions of shale gas in Qiongzhusi Formation are analyzed in detail, and the exploration and development orientation are pointed out. Firstly, a stratification standard for Qiongzhusi Formation is established. It is clarified that four sets of organic rich shale of deep shelf facies were developed in Qiongzhusi Formation (layers ①, ②, ③, and ④), which were controlled by the development of rift troughs, with the largest shale thickness in the trough. The characteristics of shale reservoirs are analyzed, which indicate that the reservoir pressure, porosity, and gas saturation show an increasing trend from bottom to top, and from the outside to the inside of the rift trough, and reservoir overpressure plays an important role in the preservation of shale pores. On this basis, an overpressure and differential shale gas enrichment mode of “different facies in multiple layers and overpressure pore preservation” in Qiongzhusi Formation has been established, and it is pointed out that the overpressure pore development area (interval) far away from the dispersion pathway is the favorable area (interval) for shale gas enrichment. Finally, the study results indicate that Well Zi 201 and its surrounding areas are the main areas for increasing shale gas reserves and production in the future, with resources of 8.06×10 12m 3. It shows considerable development potential in western Sichuan Basin, with resources of 0.72×10 12m 3. Affected by graphitization and tectonic activities, areas with overpressure pore development far from weathered crust and surface outcrops are favorable for shale gas exploration in Changning in southern Sichuan Basin and northern Guizhou Province. Reference | Related Articles | Metrics

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Zhu Chenglin, Han Yaqin, Gao Yang, Wang Jianzhong Progress and prospects of the reform of the approval and registration system for oil and gas mining rights China Petroleum Exploration    2023, 28 (6): 15-24.   DOI: 10.3969/j.issn.1672-7703.2023.06.003 Abstract （133）   HTML    PDF （532KB）（1）    Knowledge map    Save In recent years, the Central Committee of the Communist Party and the State Council of China have attached great importance to the reform of the administrative approval system, according to which the Ministry of Natural Resources has continuously promoted the reform of the approval and registration system for oil and gas mining rights. The approval and registration system for oil and gas mining rights since 1998 are reviewed. After investigation and research, the reform process of the approval and registration system for oil and gas mining rights is divided into three stages according to the characteristics of reform in various periods. The achievements of the reform and practice of the approval and registration system for oil and gas mining rights are summarized: (1) The vitality of oil and gas upstream markets has been stimulated by promoting the transformation of government functions; (2) The business environment has been improved by streamlining approval procedures; (3) The efficiency of the approval registration system has been improved by introducing “internet+”; (4) The exploration and development of oil and gas resources have been promoted by perfecting the system. In view of the current new situation, the reform of the approval and registration system for oil and gas mining rights still faces new challenges. Finally, some suggestions are proposed: (1) Further transform government functions to promote the alignment of goals between companies and government; (2) Transform management concepts to promote whole lifecycle management mode; (3) Continue to improve the approval mode of “internet+” to achieve the interoperability; (4) Optimize and improve mining rights management system to promote the increase of oil and gas reserves and production. Reference | Related Articles | Metrics

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Cui Jun, Mao Jianying, Zhao Weiyong, Shen Xiaoshuang, Deng Wen, Wang Guo Characteristics of laminated texture and petroleum geological significance of Yingxiongling shale in Qaidam Basin China Petroleum Exploration    2023, 28 (5): 43-53.   DOI: 10.3969/j.issn.1672-7703.2023.05.004 Abstract （131）   HTML    PDF （11540KB）（4）    Knowledge map    Save A set of saline lake facies shale was deposited in Ⅳ-Ⅵ oil group of the upper member of Lower Ganchaigou Formation (E 3 2) in Yingxiongling Structural Belt in Qaidam Basin, with high carbonate mineral content and well-developed laminae, in which great progress was made in the shale oil exploration. Therefore, the in-depth research should urgently be conducted on the laminated texture, depositional mechanism, and favorable lithofacies combination. The experimental results of core description, thin section identification, scanning electron microscopy and X-ray diffraction analysis show that the shale laminated texture in the study area is divided into three types, i.e., water stratified type laminated texture (Type Ⅰ) , seasonal type laminated texture (Type Ⅱ) and flood surging type laminated texture (Type Ⅲ). Type I shale shows a typical laminated texture deposited in seasonal stratified water body in saline lake, accounting for 70% of the total laminae, which is composed of clayey laminae and calcite laminae, with a single lamina thickness of 0.1-0.5 mm. In summer and autumn, the water body was stratified, and the upper water body was favorable for microbial proliferation. While in winter and spring, the water body stratification disappeared, which was beneficial to the deposition and the preservation of organic matters. In addition, Type Ⅰ laminated texture was featured by a low deposition rate, which was beneficial to the enrichment of organic matters, with an average TOC of 1.33%. Type Ⅱ laminated texture accounts for 20% of the total laminae, which is composed of clayey lamina and silty lamina, with a single lamina thickness of 0.5-1 mm. The deposition of Type Ⅱ shale was related to the seasonal variation of terrestrial inputs, showing rapid deposition rate, with an average TOC of 0.47%; The proportion of Type Ⅲ laminated texture is 10%, which is composed of clayey lamina and silty lamina, with a single lamina thickness of 0.5-2 mm, micro-scouring surface and lens-shaped siltstone veins developed, and an average TOC of 0.27%, indicating certain hydrodynamic conditions related to gravity flow and lake flow rather than non-hydrostatic environment, as well as rapid deposition rate. The shale in the study area was mainly developed in semi-deep lake, with the single sedimentary cycle including mudstone→shale→argillaceous dolomite→dolomite from bottom to top, and occasional sand gravity flow deposits. For Type Ⅰ laminated texture, the shale deposition sequence was superimposed on dolomite, with the average porosity of dolomite of 9.8%, forming good source rock and reservoir assemblage in micro scale, which was beneficial for shale oil accumulation, showing the favorable lithofacies combination of shale oil in Ganchaigou area. Macroscopically, this set of shale has high TOC, good physical properties, and high content of brittle minerals, which is an ideal interval for shale oil exploration and development in Qaidam Basin. The hydrocarbon generation potential of Type Ⅱ and Ⅲ shales is poor, which have low contribution to hydrocarbon accumulation. Reference | Related Articles | Metrics

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Liang Xing, Zhang Lei, Jiang Liwei, Shan Chang’an, Pan Feng, Luo Yufeng, Meng Yang, Wang Gaocheng, Shu Honglin, Zhu Douxing, Li Boshuo, Wang Zhendong, Yao Qiuchang, Xu Zhengyu Exploration breakthrough and resource potential of limy source rock gas in Da’an area in the western Chongqing, Sichuan Basin China Petroleum Exploration    2024, 29 (2): 30-45.   DOI: 10.3969/j.issn.1672-7703.2024.02.003 Abstract （131）      PDF （33094KB）（0）    Knowledge map    Save A major breakthrough has been made in the exploration of limy source rock gas in the first member of Maokou Formation (Mao 1 member) in Well DB1H in Da’an area in the western Chongqing, Sichuan Basin, which has important reference and demonstration significance for the intra-source exploration of limy source rock unconventional gas in the Basin. The first horizontal well DB1H was drilled to evaluate the dark limy source rock gas reservoir in Mao 1 member in Sichuan Basin and a high gas rate of 55.6×10 4 m 3/d was tested after acidizing and fracturing. The discovery process of limy source rock gas in Mao 1 member in Da’an area has systematically been introduced, and the resource prospect in Sichuan Basin has been estimated. The analysis of geological characteristics of limy source rock gas in Mao 1 member in Da’an area in the western Chongqing shows that the main lithology is composed of medium-gentle slope facies deep gray-black organic-rich micritic bioclastic limestone, with stable distribution in the region, which is an important marine limy source rock in the Middle and Upper Yangtze region in South China. The hydrocarbon accumulation process of limy source rock gas in Mao 1 member showed an “intra-source integrated evolution” of organic-rich carbonate rock deposition, diagenesis, hydrocarbon generation, reservoir formation, hydrocarbon accumulation and preservation, which had characteristics of “source rock and reservoir integration, in-situ hydrocarbon enrichment, and contiguous gas distribution”. The micro-sized pores in source rock, and the dissolution pores and micro-fracture network system associated with faults served as the main reservoir space, forming two types of reservoirs, i.e., matrix porosity type (primary) and fracture-porosity type (transformed). The hydrocarbon accumulation pattern of “mainly source rock and reservoir integration and enrichment in local structural transition zone after short-distance migration” has been established and the sweet spot evaluation system has been constructed. The key factors for gas enrichment and high-yield production in the new type of limy source rock reservoir in Mao 1 member include the development of organic rich dark limy source rock, favorable paleo uplift, anticlinal tectonic settings at present, and fault-controlled karst and extensional micro-fractures. The estimated resources of limy source rock gas in Mao 1 member are 2×10 12 m 3 in Sichuan Basin, which is a new unconventional field for increasing reserves and production in the basin. Reference | Related Articles | Metrics

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Xu Huaming, Cong Haiyue, Hou Pingshu, Wang Huiyong Issues and policy suggestions in exploration rights management of deep to ultra-deep oil and gas resources in China China Petroleum Exploration    2023, 28 (6): 70-77.   DOI: 10.3969/j.issn.1672-7703.2023.06.009 Abstract （129）   HTML    PDF （505KB）（0）    Knowledge map    Save Associated with the increasing proven degree of shallow to medium-shallow oil and gas resources, the potential of reserve increase is decreasing year by year. Therefore, increasing the petroleum exploration efforts in deep to ultra-deep formations is of great strategic significance in alleviating the pressure of insufficient annual new addition proven oil and gas reserves and ensuring national energy security. In order to ensure the full utilization of resources, promote the discovery of deep to ultra-deep oil and gas resources, and effectively coordinate resources as a whole, some optimization suggestions on the management of deep to ultra-deep mining rights are proposed. There are some issues in the management of deep to ultra-deep mining rights, for example, the period of exploration and production integration is too short, which is insufficient to transfer from exploration to production, the newly transferring deep to ultra-deep mining rights have a small scope, which is not favorable for petroleum exploration, and the overlapping exploration rights lead to duplicate investment in scientific research funds. By systematically summarizing the current exploration and development situation and potential of deep to ultra-deep oil and gas resources, issues in deep to ultra-deep mining rights management are analyzed in detail and targeted solutions are proposed as follows: (1) Renew for another 8-10 years of exploration and production integration upon expiration to ensure that oilfield companies have sufficient time to transfer from exploration to production; (2) Rationally set the size of the transfer mining rights and the renewal and relinquishment/reduction methods, encourage mineral rights holders to increase investment in new blocks, and promote the discovery of oil and gas resources; (3) Establish a special joint research team, link up the equipment, material and components, manufacturing, and application industry chain of petroleum exploration and production in deep to ultra-deep formations, so as to optimize resource investment and improve the overall efficiency of strategic resources in China. In summary, strengthening resource coordination and optimizing mining rights management policies will provide strong guarantees for high-quality and sustainable development of petroleum exploration and development in deep to ultra-deep formations in China. Reference | Related Articles | Metrics

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Tang Yong, Bai Yu, Gao Gang, He Wenjun, You Xincai, Dang Wenlong, Zhang Lei, Jiao Xiaobing, Li Mengyao, Yan Qi, Yu Xing Exploration breakthrough and geological significance of continental deep shale gas in Well Fengyun 1 in Mahu Sag China Petroleum Exploration    2024, 29 (1): 106-118.   DOI: 10.3969/j.issn.1672-7703.2024.01.008 Abstract （126）   HTML    PDF （29549KB）（0）    Knowledge map    Save The Permian Fengcheng Formation is the main source rock and exploration target in Mahu Sag, and the identification of shale oil and gas potential in deep formations has important guiding significance for further exploration activities. Based on shale gas discoveries in Fengcheng Formation in Well Fengyun 1 and exploration achievements in the underlying pre-Fengcheng Formation, the lithologic characteristics, hydrocarbon generation conditions of source rock, and reservoir conditions in Well Fengyun 1 have systematically been analyzed, and the distribution sequence of shale oil and gas in Fengcheng Formation in Mahu Sag has been determined, showing great geological significance. The study results show that Fengcheng Formation in Well Fengyun 1 is mainly composed of salt rock, shale, and silty-fine sandstone; Fengcheng Formation source rock has a relatively low organic matter abundance, and that in the first member has the best quality, with an average TOC of 1.06%; The reservoir is generally tight with an average porosity of 4.65%, and the dolomitic shale and limy sandstone have relatively better physical properties. With the increasing depth, a complete hydrocarbon distribution pattern from shale oil, to shale oil and gas, and to shale gas occurs in Fengcheng Formation in Mahu Sag. In addition, pre-Fengcheng Formation shows good resource potential with hydrocarbon source supplied by the ultra-deep oil and gas system, which is a major field for further exploration. Reference | Related Articles | Metrics

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Hu Xuguang, Li Qian, Luo Yuan, Pang Ping, Liu Guiyi, Luo Weihua, Qing Yu Key technology and prospect of snubbing operation in gas well China Petroleum Exploration    2023, 28 (5): 135-144.   DOI: 10.3969/j.issn.1672-7703.2023.05.012 Abstract （125）   HTML    PDF （1737KB）（9）    Knowledge map    Save At present, gas well snubbing operation is an important completion and workover technology in the global gas field development, which enables to avoid reservoir damage caused by conventional well killing operation, and has outstanding technical advantages such as reservoir protection, cost reduction and efficiency improvement. In view of the prominent technical problems such as short service life of annulus motive sealing wear-resistant parts in gas well snubbing operation, low pressure grade of inner pipe string sealing tools, and high risk of pipe string flying out and bending, research has been conducted on four aspects, including pressure control technology of annulus motive seal, pressure control technology of inner pipe string sealing, anti-pipe string flying out technology and anti-pressure bending technology. The motive sealing wear-resistant parts with a service life of over 1200m at the wellhead pressure of 35MPa have been developed, as well as the inner pipe string sealing tools at a pressure of 70MPa. The calculation formula of neutralization point and the calculation model of ultimate bending length of pipe strings have been established. The research results have successfully broken through technical bottlenecks such as annular motive sealing and inner pipe string sealing, and formed key technology of gas well snubbing operation, which have been applied for more than 1000 wells in PetroChina Changning-Weiyuan, Changqing Oilfield and Sinopec Fuling blocks, greatly improving the technical capability and efficiency of snubbing operation in gas wells, and obtaining significant results of production increase. The research shows that the key technology of gas well snubbing operation provides powerful technical support for conventional gas well workover and large-scale completion of shale gas wells. Reference | Related Articles | Metrics

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Yang Jinyu, Chen Xiaoping, Li Chao, Zheng Kui, Zhang Baojuan, Chen Chunheng Optimization of infill adjustment parameters of horizontal shale oil wells based on economic benefit evaluation: a case study of shale oil reservoir in the seventh member of Yanchang Formation in XAB Oilfield, Ordos Basin China Petroleum Exploration    2023, 28 (4): 129-138.   DOI: 10.3969/j.issn.1672-7703.2023.04.012 Abstract （120）   HTML    PDF （4434KB）（2）    Knowledge map    Save XAB Oilfield in Ordos Basin is located in Dingbian, Shaanxi Province. The main target layer is the shale interval in the seventh member of the Upper Triassic Yanchang Formation (Chang 7 member), with tight shale reservoir and high-angle fractures widely developed. Since 2011, rolling capacity construction and development by horizontal wells have been applied to produce the shale oil reservoir, which have the problem of low oil recovery degree and low production rate. In recent years, in order to research the high-efficiency shale oil development mode, tests of inter-well infill adjustment in horizontal well development zone have been conducted, and good results have been achieved in increasing oil production. Based on understanding of infill adjustment tests in the early stage, a “matrix-fracture” dual medium numerical model is established by fully considering the natural fracture features in the study area, and the infill adjustment parameters are optimized for horizontal well development zones with various production years, with the main parameters including infill timing, hydraulic fracture layout, horizontal well spacing and half-length of hydraulic fractures. A total of 76 infill adjustment schemes are designed to simulate and calculate the cumulative oil production of various schemed during the evaluation period. Furthermore, the financial net present value ratio is calculated and the economically beneficial schemes are ranked and optimally selected by using the financial cash flow method. The study results show that: (1) The longer the production period of the horizontal well development zone, the poorer results of infill wells. (2) The staggered layout pattern is better than the symmetrical layout pattern of hydraulic fractures. (3) The optimal infill adjustment parameters vary given the different infill timings. When the infill timing is 2-10 years, the optimal infill well spacing is 260 m, and the optimal half-length of the hydraulic fracture ranges in 140-180 m. On this basis, the horizontal infill adjustment design for Chang 7 member shale oil in horizontal well development zone in XBA Oilfield is conducted. After infill adjustment, the oil recovery factor and net present value ratio are expected to increase by 1.05% and 0.013 respectively, which supports to improve the shale oil development results and achieve good economic benefits. Reference | Related Articles | Metrics

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Guo Delong, Shen Yinghao, Lin Hai, Xiong Tingsong, Zhao Jian, Wang Xiaoqiong, Wu Kunyu, Zhao Wenkai, Xing Haoting, Zhang Jing, Feng Xiyuan, Xiao Qian, Zhao Endong, Zhang Shaobin, Zhang Muyang Post fracturing shale oil sweet spot evaluation in Well CP1 in Yingxiongling area, Qaidam Basin China Petroleum Exploration    2023, 28 (4): 117-128.   DOI: 10.3969/j.issn.1672-7703.2023.04.011 Abstract （115）   HTML    PDF （5791KB）（2）    Knowledge map    Save In 2021, breakthrough of high-yield shale oil production was achieved in Well CP1 in Yingxiongling area in Qaidam Basin. However, it is still necessary to determine the dominant sweet spot lithofacies between the two preliminarily identified sweet spots, i.e., laminated limy-dolomitic shale and layered limy-dolomitic shale. The geological and engineering sweet spot lithofacies of shale oil in Yingxiongling area are systematically analyzed from the perspectives of organic matter abundance, physical properties, oil-bearing property, fracture complexity after fracturing, tracer, and production performance. The results show that: (1) The indicators characterizing the geological sweet spots of Yingxiongling shale oil include carbonate content, oil saturation, and TOC, while the fracability is a key parameter to characterize the engineering sweet spots. (2) Compared with the layered limy-dolomitic shale, the laminated limy-dolomitic shale has advantages of oil saturation, horizontal permeability, fracture complexity, imbibition ability, oil phase flow ability, and oil breakthrough rate. (3) The laminated limy-dolomitic shale is geological and engineering sweet spots in Yingxiongling area. (4) In practice, it is suggested that the No.3 thin layer of the No.11 layer in the IV oil group of the upper part in Lower Ganchaigou Formation (E32-Ⅳ-11-3) is targeted for shale oil exploration and development. Reference | Related Articles | Metrics