Article
Geochemistry & Geophysics
Wang Zhang, Xinping Liang, Peng Li, Guoheng Liu, Jin Qian
Summary: Significant amounts of unconventional oil and gas resources have been discovered in the Yanchang Formation of Ordos Basin, primarily sourced from the shale layers in Chang 7 and 9 members. The C7-3 submember shale has the highest content of illite/smectite mixed layer and reducing minerals, while the C9 member shale has the highest percentage of quartz and illite. The C7-3 submember shale is characterized by high productivity due to type II1 kerogen, and the C9 member shale exhibits the highest organic thermal maturity.
Article
Geosciences, Multidisciplinary
Songtao Wu, Shixiang Li, Xuanjun Yuan, Zhi Yang, Aifen Li, Jingwei Cui, Songqi Pan, Zhiguo Mao, Ling Su, You Zhou
Summary: Various types of pores were identified in the Chang 7 tight sandstones using methods like NMR, and it was found that pore connectivity is positively correlated with physical properties, which is crucial for evaluating fluid mobility in tight reservoirs.
JOURNAL OF EARTH SCIENCE
(2021)
Article
Geosciences, Multidisciplinary
Guanglin Liu, Xianyang Liu, Xiaofeng Ma, Shuang Ma, Xiaofeng Wang, Shuo Li, Zhiqiang Shi, Yanxin Wang
Summary: In this study, the petrology, microstructure, and geochemistry of the laminated calcite veins in the black shale of Chang 73 submember in the Ordos Basin were investigated. The results provide insights into the origin, formation mechanism, and dynamic background of the veins. The veins are predominantly composed of calcite and contain solid wall rock inclusions. The calcite minerals exhibit fibrous, rhombic cleavage, and wedge-like structures. Trace elements and isotopic geochemistry confirm that the calcite veins formed from a high-density hydrothermal fluid. The study suggests that the calcite veins formed prior to wall rock consolidation during the formation of the Qinling Orogenic Belt in the Middle and Late Triassic. The findings also indicate that the sedimentary sources of the Chang 73 submember were influenced by hydrothermal materials. Moreover, the fibrous calcite identified in this study differs from previously reported fibrous calcite in terms of morphology and formation mechanism.
ACTA GEOLOGICA SINICA-ENGLISH EDITION
(2023)
Article
Geosciences, Multidisciplinary
Beibei Luan, Bo Zhang, Didong Wang, Chao Deng, Feng Wang
Summary: This paper systematically studies the geological characteristics and influencing factors of tight oil reservoirs, using the Chang 8 Member of the Yanchang Formation in the southern Ordos Basin as an example. The research results reveal the sedimentary facies types, microscopic pore structures, diagenesis, influencing factors of physical properties, and hydrocarbon enrichment law of tight oil reservoirs.
FRONTIERS IN EARTH SCIENCE
(2022)
Article
Energy & Fuels
Jiyuan You, Yiqun Liu, Yijun Li, Dingwu Zhou, Qinghua Zheng, Yiyao Yang, Jian Shi, Haofeng Gao
Summary: The Chang 7 oil shales in the Triassic Yanchang Formation show significant positive anomalies in Cs, U, Th, Pb, and Mn, and negative anomalies in Eu and Ta. The TOC values vary across different sections, and there is a strong correlation between hydrothermal input intensity and TOC content.
JOURNAL OF PETROLEUM SCIENCE AND ENGINEERING
(2021)
Article
Geochemistry & Geophysics
Bojiang Fan, Xinyang Dai, Chi Wang
Summary: This study comprehensively compared and analyzed the geochemical characteristics of desorption gas in the Chang 7 Member shale. The results showed that the shale gas mainly consists of CH4, C2H6, and C3H8. Porosity, permeability, and organic matter content are the main geological factors controlling gas migration and hosting. Shale with higher porosity, good permeability, and lower organic matter content is conducive to gas migration. The sandy laminated shale with a higher gas content may be the sweet spot of shale gas targets.
Article
Energy & Fuels
Fan Jianming, Shi Jian, Wan Xiaolong, Xie Qichao, Wang Chong
Summary: The Chang 7 oil group in the Ordos Basin has been evaluated for sweetness classification through a combination of field practice and laboratory experiments, providing a reference basis for optimal well design.
JOURNAL OF PETROLEUM EXPLORATION AND PRODUCTION TECHNOLOGY
(2022)
Article
Energy & Fuels
Ziye Wang, Zhiguo Mao, Xuanjun Yuan, Xiuqin Deng, Xiao Hui, Zhongyi Zhang, Jingwei Cui
Summary: Through analysis of core observation, thin section identification, and logging and testing data, the types and characteristics of event deposits in the ninth member of Yanchang Formation in southwestern Ordos Basin, China, were examined. There are four types and nine subtypes of event deposits, including earthquake, gravity flow, volcanic, and anoxic deposits. The research found that these event deposits have intrinsic genetic relations and distribution laws. Furthermore, the genetic model of event deposits and the development of various types of deposits were discussed.
PETROLEUM EXPLORATION AND DEVELOPMENT
(2023)
Article
Energy & Fuels
Qiheng Guo, Shixiang Li, Zhenkui Jin, Xinping Zhou, Chenglin Liu
Summary: The geological characteristics and enrichment laws of the shale oil in the third submember of Triassic Yanchang Formation in the Ordos Basin were analyzed, and the exploration potential and orientation of the shale oil were discussed. Two types of shale oil, migratory-retained and retained, were recognized, with the former being slightly better in quality. High-quality source rocks provide a large quantity of hydrocarbon-rich fluids, with various factors such as interbeds, fractures, and sandstone layers contributing to oil accumulation and migration. The sand-rich areas around the depression are the main targets for exploring migratory-retained shale oil, while mature deep depression areas are the main targets for exploring retained oil.
PETROLEUM EXPLORATION AND DEVELOPMENT
(2023)
Article
Geosciences, Multidisciplinary
Jingru Yang, Xianyang Liu, Wanglin Xu
Summary: This study investigates the differential accumulation of tight oil in the Chang 8 member of the Longdong area in the Ordos Basin. Through paleo-hydrodynamic restoration technology and mudstone compaction analysis, the study accurately restores the oil migration dynamics during the main reservoir-forming period. The results show that tight oil tends to migrate from the north and northeast to the southwest and accumulates in the nose-like paleo-structure in the southwest. The intensity of oil migration dynamics changes and affects the differential accumulation of tight oil.
FRONTIERS IN EARTH SCIENCE
(2022)
Article
Energy & Fuels
Qiulei Guo, Yue Yao, Lianhua Hou, Shuheng Tang, Songqi Pan, Feng Yang
Summary: This study investigates the retention, migration, and accumulation of oil in a lacustrine shale system from the Upper Triassic Yanchang Formation, Ordos Basin. The research findings demonstrate the impact of lithofacies on oil composition and amount stored in the shale systems. Organic-rich shale lithofacies retain a large amount of oil, while thin organic-lean siltstones act as reservoir units for migrated petroleum. The study also reveals the influence of pore structure on oil retention and migration.
INTERNATIONAL JOURNAL OF COAL GEOLOGY
(2022)
Article
Green & Sustainable Science & Technology
Jiayu Zheng, Zhigang Wen, Chenjun Wu
Summary: This study focuses on the description and evaluation of the ultra-low-permeability lithological reservoir in the Dalugou area of the Jing'an Oilfield, which belongs to the Chang 6 member of the Triassic Yanchang Formation. The study reveals that the reservoir in the study area is mainly underwater distributary channel deposition, with two main depositional patterns: dendritic sandstone and lobate sandstone. The heterogeneity of the reservoir under different depositional patterns has a significant influence on oil enrichment.
Article
Geosciences, Multidisciplinary
Xiaobing Niu, Tian Yang, Yingchang Cao, Shixiang Li, Xinping Zhou, Kelai Xi, Thomas J. H. Dodd
Summary: Understanding the formation processes, distribution patterns, and depositional models of gravity-flow deposits is essential for predicting and modeling sandstone bodies in subsurface lacustrine basins, which is crucial for oil and gas exploration and development. This study analyzed the gravity-flow deposits of Yanchang Formation in the Ordos Basin using various methods, including well-log analysis, core observations, thin-section analysis, and laboratory measurements. The results identified different sedimentary facies and bed types of gravity-flow deposits, with different formation mechanisms and distribution patterns.
MARINE AND PETROLEUM GEOLOGY
(2023)
Article
Energy & Fuels
Juan Teng, Hucheng Deng, Yu Xia, Wenling Chen, Meiyan Fu
Summary: Organic matter composition plays a crucial role in determining the hydrocarbon generation potential of black shales, with significant differences observed in AOM type and content between shales from different regions.
Article
Geosciences, Multidisciplinary
Qi Ni, Wen Zhou, Gensheng Ni, Tao Li, Wen Wu, Minwei Wang
Summary: This study investigates the evolution and prediction of natural fractures in tight sandstones using core, thin section, logging materials, and numerical simulation methods. The results show that vertical and horizontal sliding fractures with shearing properties are developed in the tight sandstones. The particle size affects the compactible space inside the reservoir, which then affects the fracture development degree. Fractures are more developed in thin sand bodies, and their controlling factors include lithology, sedimentary microfacies, sand thickness, and local structure. A comprehensive evaluation of fractures in tight sandstones from 1D to 3D was achieved using core observation, logging interpretation, and three-dimensional fracture modeling.
GEOLOGICAL JOURNAL
(2023)
