Hydrocarbon accumulation period and geochemical discrimination of gas-bearing properties of deep tight sandstone in Kuqa depression, China

In order to clarify the hydrocarbon accumulation period of deep tight sandstone in Dabei-Keshen area of Kuqa depression, and to develop identification methods of reservoir fluid properties, a series of experiments were carried out. The results show that hydrocarbon inclusions are less distributed, and gaseous hydrocarbon is mainly methane. Hydrocarbon has been continuously charged since 12Ma in Dabei gas field, and one main period of accumulation took place during 6-4Ma for Keshen gas field. Late accumulation may limit the application of hydrocarbon inclusions abundance, rock soluble salt components to distinguish reservoir fluid properties. Carbon isotope composition of carbonate cement in tight sandstone is an effective indicator for gas-bearing properties. For gas layer, the carbon isotope is lighter than -1.5 parts per thousand and -2.5 parts per thousand for Dabei and Keshen gas field receptively.