Distribution pattern of natural fractures in lacustrine shales: a case study of the Fengcheng formation in the Mahu Sag of the Junggar Basin, China

Frontiers in Earth Science

Earth Science

Guoqing Lu¹  Guoping Liu²  Xiaoyu Du²  Lianbo Zeng³  Zhijun Jin⁴  Sen Yang⁵  Wenjun He⁵  Guoyong Liu⁵ 

[1] College of Geosciences, China University of Petroleum (Beijing), Beijing, China;Institute of Energy, Peking University, Beijing, China;Institute of Energy, Peking University, Beijing, China;College of Geosciences, China University of Petroleum (Beijing), Beijing, China;Institute of Energy, Peking University, Beijing, China;State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Effective Development, Beijing, China;Research Institute of Exploration and Development, Xinjiang Oilfield Company, PetroChina, Karamay, China;

关键词: natural fractures;    distribution patterns;    lacustrine shale;    Fengcheng formation;    Mahu sag;   

DOI  :  10.3389/feart.2023.1207033

 received in 2023-04-17, accepted in 2023-05-09,  发布年份 2023

来源: Frontiers

【 摘 要 】

The Lower Permian Fengcheng Formation in the Mahu Sag develops a set of organic-rich alkaline lacustrine shale strata, which is a key area for shale oil exploration and development. As an important storage space and seepage channel for shale reservoirs, natural fractures have an impact on shale oil enrichment, production and development effect. In this study, the types and characteristics of natural fractures were first analyzed using core, thin section and imaging logging data. On this basis, combined with the distribution of fractures in single wells, the vertical distribution law of fractures is discussed. Finally, the planar distribution of fractures is evaluated using different seismic attributes such as coherence, curvature, likelihood, and AVAz. The results showed that three types of fractures are existed, including transformational shear fractures, intraformational open fractures and bed-parallel shear fractures, with intraformational open fractures being the most developed. The development degree of fractures in different layers has obvious differences, mainly controlled by lithology and brittle mineral content. The basalt and tuff are developed in the Feng 1 Member, with low carbonate mineral content, resulting in a relatively low degree of fracture development. The dolomite and argillaceous dolomite are developed in the Feng 2 Member and the Feng 3 Member, with high carbonate mineral content and brittleness, resulting in a high degree of fracture development. Additionally, the closer to the fault, the higher the degree of fracture development. On the plane, the fracture zone develops near the main and secondary faults, with the trend mainly oriented in the E-W direction and approximately parallel to the direction of the faults. The width of the fracture zone is largest in the central and southern part of the study area. These fractures are fault-related and are caused by regional stress fields resulting from the activity of the main-secondary faults.

【 授权许可】

Unknown   
Copyright © 2023 Liu, Jin, Yang, Zeng, He, Du, Lu and Liu.