Distribution characteristics, exploration & development, geological theories research progress and exploration directions of shale gas in China
Shizhen Li, ,Oil and Gas Survey, China Geological Survey, Ministry of Natural Resources, Beijing 100083, China, Zhi Zhou, Haikuan Nie, Lei-fu Zhang, Teng Song, Weibin Liu, Hao-han Li, Qiuchen Xu, Si-yu Wei, Shu Tao
Abstract
The shale gas resources in China have great potential and they are distributed in 13 stratigraphic series from the Mesoproterozoic to the Cenozoic. Organic-rich shales can be divided into three types according to their sedimentary environments, namely marine, marine-continental transitional, and continental shales. The geological resources of shale gas in China is over 100 trillion m<sup>3</sup>, which includes 20 trillion m<sup>3</sup> of recoverable resources. The Sichuan Basin and its surrounding areas have the highest geological resources of shale gas, and the commercial development of shale gas has been achieved in the Upper Ordovician Wufeng Formation - Lower Silurian Longmaxi Formation in these areas, with a shale gas production of up to 20 ×10<sup>9</sup> m<sup>3</sup> in 2020. China has seen rapid shale gas exploration and development over the last five years, successively achieving breakthroughs and important findings in many areas and strata. The details are as follows. (1) Large-scale development of middle-shallow shale gas (burial depth: less than 3500 m) has been realized, with the productivity having rapidly increased; (2) Breakthroughs have been constantly made in the development of deep shale gas (burial depth: 3500‒4500 m), and the ultra-deep shale gas (burial depth: greater than 4500 m) is under testing; (3) Breakthroughs have been made in the development of normal-pressure shale gas, and the assessment of the shale gas in complex tectonic areas is being accelerated; (4) Shale gas has been frequently discovered in new areas and new strata, exhibiting a great prospect. Based on the exploration and development practice, three aspects of consensus have been gradually reached on the research progress in the geological theories of shale gas achieved in China. (1) In terms of deep-water fine-grained sediments, organic-rich shales are the base for the formation of shale gas; (2) In terms of high-quality reservoirs, the development of micro-nano organic matter-hosted pores serves as the core of shale gas accumulation; (3) In terms of preservation conditions, weak structural transformation, a moderate degree of thermal evolution, and a high pressure coefficient are the key to shale gas enrichment. As a type of important low-carbon fossil energy, shale gas will play an increasingly important role in achieving the strategic goals of peak carbon dioxide emissions and carbon neutrality. Based on the in-depth study of shale gas geological conditions and current exploration progress, three important directions for shale gas exploration in China in the next five years are put forward.