Densification Mechanism and Natural Gas Accumulation Process, Triassic Xujiahe Formation, Hechuan Area, Sichuan Basin, China

Abstract

We have witnessed a skyrocketing development of tight gas in China. However, all developed gas field in China face the obstacle of the decrease of production. The Xujiahe Formation in Sichuan Basin shows a promising future for the next big gas field. In this work, we will shed light on the densification mechanism and natural gas accumulation process of Triassic Xujiahe Formation, Hechuan Area, Sichuan Basin through physical experiments and theory analysis. We describe the reservoir characteristics. The diagenesis types and characteristics of sandstone reservoirs in the promising future of the next big gas field. In this work, we will shed light on the densification mechanism and natural gas accumulation process of Triassic Xujiahe Formation, Hechuan Area, Sichuan Basin through physical experiments and theory analysis. We describe the reservoir characteristics. The diagenesis types and characteristics of sandstone reservoirs in the second Member of Xujiahe Formation in Hechuan area are analyzed by means of rock thin section, cast thin section, and mercury injection. By observing the microscopic characteristics, types, and homogenization temperature distribution of fluid inclusions, the accumulation period of natural gas in Hechuan gas field is given, and the accumulation process of natural gas is revealed. The results show that (1) the natural gas charging the tight sandstone reservoirs of the Upper Triassic Xujiahe Formation in Hechuan area is a continuous process. The gas accumulation period can be roughly divided into two stages; (2) combining with the analysis of the hydrocarbon accumulation period of time, we put forward the natural gas accumulation model of the Xujiahe Formation, Hechuan area: the natural gas accumulation is accompanied by formation densification.