China Petroleum Exploration ›› 2021, Vol. 26 ›› Issue (6): 21-37.DOI: 10.3969/j.issn.1672-7703.2021.06.002

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Major discovery and high-efficiency development strategy of shallow shale gas:a case study of Taiyang shale gas field

Liang Xing1,Zhang Jiehui1, Zhang Hanbing1,Xu Zhengyu2,Zhang Dongtao1,Zhu Douxing3   

  1. 1 PetroChina Zhejiang Oilfield Company; 2 PetroChina Hangzhou Research institute of Geology; 3 Research Institute of BGP Inc., CNPC
  • Online:2021-11-15 Published:2021-11-15

Abstract: In order to find out the gas occurrence conditions and controlling factors for high yield well of shallow shale gas in complex structural zone in the peripheral Sichuan Basin, expand exploration field of shale gas in mountainous area and achieve the high-efficiency development of shallow shale gas in southern China, PetroChina Zhejiang Oilfield Company has conducted reexamination on old wells,fracturing and testing on shallow shale gas wells in Zhaotong demonstration area, and obtained a new understanding that a “3D sealing box” is formed jointly by roof/floor cap rocks of shallow shale gas and self-sealing of shale reservoir. By considering the geological and surface conditions, an operation technology of integrated geology and engineering for shale gas in mountainous area has been implemented, which achieved a major discovery and commercial development of the first shallow shale gas field in China. The study results show that the sweet spots, gas enrichment and high production of shallow shale gas are controlled by “multi-factor coupling”, that is, shale gas accumulation is controlled by lithofacies, deformation intensity in the tectonic reconstruction period and sealing capability in the gas accumulation period.The shale burial depth, formation dip, denudation intensity and fluid potential jointly control the occurrence of shale gas. Specially, it is proposed that the “dynamic balance of shale gas accumulation and dispersion” is the key factor for the effective occurrence and enrichment of shallow shale gas of Taiyang gas field, which is complemented by slow gas dispersion owning to the shale self-sealing preservation and bed parallel super-short distance gas migration and accumulation. After the verification by field practice, three major countermeasures have innovatively been formed for high-efficiency development of shallow shale gas, including refinement of development and evaluation units of gas field, integrated drilling deployment and optimization, and personalized design of drilling platform, as well as the economical and practical technology series for drilling, fracturing and production.

Key words: shallow shale gas, integrated geology and engineering, self-sealing of shale, exploration breakthrough, high-efficiency development, Taiyang shale gas field

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