China Petroleum Exploration ›› 2022, Vol. 27 ›› Issue (3): 110-120.DOI: 10.3969/j.issn.1672-7703.2022.03.010

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Reservoir characteristics and key technologies for shale gas exploration and development of the first member of the Permian Shanxi Formation in Yan’an area

Sun Jianbo1,2,Hao Shiyan1,2,Zhao Qianping1,2,Luo Tengyue1,2,Jiang Lei3,Gao Chao1,2,Guo Chao1,2,Yin Jintao1,2,Liu Gang1,2,Xu Jie1,2   

  1. 1 Research Institute of Shaanxi Yanchang Petroleum (Group) Co. Ltd.; 2 Shaanxi Key Laboratory of Continental Shale Gas Accumulation and Exploitation; 3 Oil and Gas Exploration Company, Shaanxi Yanchang Petroleum (Group) Co. Ltd.
  • Online:2022-05-15 Published:2022-05-13

Abstract: There are abundant shale gas resources in the first member of the Permian Shanxi Formation (Shan 1 member) in Yan’an area. However, the shale reservoir has strong heterogeneity and the geological conditions for gas accumulation are complex. There are abundant shale gas resources in the first member of the Permian Shanxi Formation (Shan 1 member) in Yan’an area. However, the shale reservoir has strong heterogeneity and the geological conditions for gas accumulation are complex. Based on the geological and engineering characteristics of shale gas in Shan 1 member, systematic study and technology research are conducted by using drilling, logging, fracturing, core experiment and well testing data, so as to identify the exploration potential of shale gas in the study area. In addition, key technologies for the exploration and development of continental shale gas are developed. The results show that the interbedding of sand and shale is developed in Shan 1 member with rapid lithofacies changes laterally. The shale is generally gas-bearing, as well as the adjacent sandstone, which is characterized by the mixture of sand and shale and compound gas accumulation. The cumulative shale thickness of Shan 1 member is 25m on average, and the formation pressure coefficient is 0.82. The organic matter is dominated by Type III kerogen, with Ro of between 2.33%-2.85%. Four types of pores and two types of fractures are developed in shale, and the average content of desorption gas is 1.2m3/t. The average gas saturation of the adjacent sandstone is 45%, and the average porosity is 7.2%. The integrated and innovative researches enable to initially develop a series of key technologies, such as “three qualities” logging evaluation of continental shale gas, shale gas reservoir recognition and geosteering while drilling, optimal and fast drilling of horizontal well with low cost, and CO2 mixed volume fracturing of horizontal well, which strongly support shale gas exploration and development in Yan’an area. Three horizontal wells have been drilled, with drilling time decrease of 11.3%, average thin sandstones penetration rate of more than 75%, and an open flow rate of more than 6×104m3/d.

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