ABSTRACT
The deep layers of the Dehui fault depression in the Songliao Basin have great potential for natural gas resources. With the continuous development of oil and gas accumulation theory, the understanding of the geochemical characteristics and genesis of deep natural gas in the Dehui fault depression is relatively backward, which seriously restricts the exploration and development and requires further detailed evaluation. Based on the collection of 122 natural gas samples, this paper analyzes the hydrocarbon and non-hydrocarbon gas components and carbon isotope characteristics of the samples by analyzing and testing experiments and identifying the genetic type in combination with the relationship between hydrocarbon gas components and carbon isotopes. The results show that the hydrocarbon components of the natural gas in the Dehui fault depression are mainly alkane gas. Among them, the average content of methane is 86%, the average content of ethane is 4.2%, and the average content of propane is 1.7%. The distribution of the drying coefficient of natural gas is 0.75~0.99, which reflects that the natural gas is mainly wet. Non-hydrocarbon components mainly include N2 and CO2, and the content is mainly concentrated in 2%~6% and 0.02%~1%. The carbon isotope characteristics of alkanes show that the distribution of δ 13C1 ranges from −50‰ to −26‰, the distribution range of δ 13C2 ranges from −35‰ to −20‰, and the distribution of δ 13C3 ranges from −33‰ to −24‰. Natural gas is mainly coal-derived, mixed with a small amount of oil-cracking gas and mixed gas. The results of the research can provide theoretical help for the further exploration and development of deep natural gas in the Dehui fault depression.
