Xinjiang Petroleum Geology ›› 2023, Vol. 44 ›› Issue (5): 535-542.doi: 10.7657/XJPG20230504

• OIL AND GAS EXPLORATION • Previous Articles     Next Articles

Characteristics of Fractures and Their Controls on Yanchang Formation Reservoir in Ordos Basin

XIAO Zhenglu1(), LU Jungang1(), LI Yong1, ZHANG Hai2, YIN Xiangdong1, ZHOU Xiang1   

  1. 1. Southwest Petroleum University, a.National Key Laboratory of Oil and Gas Reservoir Geology and Exploitation; b.Sichuan Key Laboratory of Natural Gas Geology; c.School of Geoscience and Technology, Chengdu, Sichuan 610500, China
    2. Jingbian Oil Production Plant, Yanchang Oilfield Co., Ltd., Yan’an, Shaanxi 716000, China
  • Received:2023-04-11 Revised:2023-06-16 Online:2023-10-01 Published:2023-09-25

Abstract:

In order to determine the temporal continuity and spatial orderliness of hydrocarbon charging and accumulation in fault areas, taking the Shangzhenzi farm-Zhuanjiao area at the southern margin of the Ordos basin as an example, the relationship between fracture formation period and reservoir distribution was analyzed, and the controls of fractures on Yanchang formation reservoir was discussed. The study shows that the fractures of three periods (Yanshanian movement episode II and III, and Himalayan movement) are developed in Yanchang formation, showing varying impacts on hydrocarbon migration and accumulation. Near-source oil reservoirs captured all the hydrocarbons generated from the source rocks in immature and mature stages, which were subsequently destroyed during the Yanshanian episode III and the Himalayan movement, leading to oil migration towards the areas far away from source rocks. In the southern part of the study area, close to the Weibei uplift, fractures are well connected longitudinally and sand bodies are well developed, allowing oil enrichment primarily in reservoirs far away from source rocks. In the northern part of the study area, oil is predominantly retained in reservoirs near source rocks. Consequently, fractures and sand bodies are connected to form a transport network that plays a role in adjusting reservoirs. By virtue of multi-stage fractures, resources in reservoirs near or far away from source rocks can be complemented and integrated.

Key words: Ordos basin, Yanchang formation, fracture, hydrocarbon accumulation, reservoir-controlling mechanism, differential accumula-tion, secondary adjustment

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