Gas accumulation models and characteristics of gas fields in China

Abstract

Due to different accumulation conditions between natural gas and oil, as well as the complexity of geological settings of the main gas bearing basins in China, accumulation of natural gas in Chinese gas fields is a complex process. In terms of timing of gas charging and entrapment, gas fields in China can be grouped into four types: fields with super late (Neogene–Quaternary) gas generation, migration and entrapment; fields with late (Paleogene–Neogene) gas generation, migration and entrapment; fields characterized by late (Tertiary–Quaternary) secondary accumulation of gas generated and accumulated earlier (primarily Mesozoic); and fields with early (primarily Mesozoic) gas generation, migration and entrapment. The first three types are all finalized during the Himalayan period. The Himalayan tectonic movements have, therefore, significant effects on the formation and distribution characteristics of natural gas pools in China. Currently, we are focusing our gas exploration in three major areas: the foreland basins in west–central China, three cratonic superimposed basins (Sichuan, Ordos and Tarim) and offshore rift basins. In these gas-rich basins, the final gas charging and entrapment took place in late and super late stages.