China Petroleum Exploration ›› 2020, Vol. 25 ›› Issue (2): 33-42.DOI: 10.3969/j.issn.1672-7703.2020.02.004

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Progress, challenges and prospects for continental shale gas exploration and development in the Yanchang exploration area of the Ordos Basin

Du Yan1,2,3, Liu Chao1,2,3,Gao Chao1,2,3,Guo Chao1,2,3,Liu Gang1,2,3,Xu Jie1,2,3,Xue Pei1,2,3   

  1. 1 Research Institute of Shaanxi Yanchang Petroleum (Group) Co., Ltd.; 2 Shaanxi Key Laboratory of Continental Shale Gas Accumulation and Exploitation; 3 China Petroleum and Chemical Industry Continental Shale Gas Engineering Research Center
  • Online:2020-03-15 Published:2020-03-13
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Abstract: As a large oil and gas-rich superimposed basin, the Ordos basin develops multiple sets of Permian and Triassic continental shale strata and is abundant in shale gas resources. Compared with marine shale, continental shale is more complicated, and there are many challenges during its exploration and development which restrict its economic exploitation. In this paper, achievements in the practice of continental shale gas exploration and development in the Ordos basin are summarized in terms of geological characteristics, resources background, and exploration and development technologies. In addition, the current technical difficulties of continental shale gas development are analyzed in order to effectively, and in a timely manner, utilize opportunities and approach challenges in the development process. According to comprehensive analysis, shale gas parameters in the Yanchang exploration area, such as continental shale thickness, total organic carbon content, maturity, and gas content, are above the lower limit for favorable shale gas intervals stipulated by national standards, so the continental shale in the basin possesses the geological conditions for gas accumulation. Under the control factors of macro and micro heterogeneity, continental shale gas has different enrichment characteristics in terms of phase state and scale. There are two types of accumulation modes; adsorption gas accumulation, and adsorption + free gas composite accumulation. Understanding of the different accumulation mechanisms guides the selection of favorable zones and production from continental shale gas wells. A number of key supporting technologies have been formed during the practice of continental shale gas exploration. Logging evaluation methods suitable for strongly heterogeneous continental shale have been established. A water-based drilling fluid system and a series of supporting equipment for drilling and completion have been developed. A CO2 fracturing technology system and wellsite waste fluid recovery and treatment- utilization technology have also been formed. Meanwhile, there are still many challenges in terms of precise prediction of “sweet spots”, acceleration and efficiency of drilling, environmental protection, efficiency of fracturing, and cost reduction. At present, the exploration and development of continental shale gas in China is still in an early stage, with high costs and low initial production. It is still necessary to carry out pilot tests of exploration and development to achieve scientific and technological breakthroughs, develop continental shale gas as a resource replacement, and promote the continental shale gas industry to obtain economic benefits.

 

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