Advances, challenges, and countermeasures in shale gas exploration of underexplored plays, sequences and new types in China

In recent years, China has shifted its focus of shale gas exploration to underexplored plays, sequences and new types (collectively referred to as the “three new fields”). This shift has led to intensified efforts in addressing theoretical challenges and enhanced exploration, elevating both the reserves and production of shale gas to new levels. Based on new advances in theoretical research and exploration in the three new fields, we analyze the characteristics, trends, and prospects of shale gas exploration in these fields, explore theories on the unique shale gas geology in China, and identify challenges in shale gas exploration and corresponding countermeasures. The results indicate that China has developed innovative theories on the enrichment of highly-to over-mature marine shale gas with distinct characteristics of shales in the Wufeng-Longmaxi formations within the Sichuan Basin and its surrounding areas. A total of nine shale gas fields have been discovered in China with proven geological reserves of approximately 3×10¹² m³, resulting in a shale gas productivity of 450×10⁸ m³/a, and an annual shale gas production of 250×10⁸ m³. Furthermore, we ascertain three majorcharacteristics of the shale gas exploration in the three new fields in China: (1) significant progress in deep and extremely shallow strata for shale gas exploration of the Wufeng-Longmaxi formations within the Sichuan Basin and its surrounding areas; (2) breakthroughs in multiple underexplored units, such as the Qiongzhusi and Wujiaping formations in the Sichuan Basin; and (3) discoveries and breakthroughs in the Wulalike and Shanxi formations located on the western and eastern margins of the Ordos Basin, respectively. Three major strategic shifts have been achieved: (1) a shift in exploration target from a single type, basin, and unit to multiple types, basins, and units; (2) a shift of target area selection from focusing on the interiors or peripheries of basins to including basins’ exterior with weak tectonic modification; (3) a shift in the exploration philosophy from pure organic-rich shales to organic-rich shale systems. Analyzing challenges in shale gas exploration in the three new fields in China leads to the conclusion that these fields both represent the direction for the sustainable development of shale gas in China and need corresponding countermeasures for their progress.