Genetic Types and Gas Source Analysis of Jurassic Deep Coalbed Methane in Baijiahai Uplift, Junggar Basin

Multiple sets of source rocks are developed in the Baijiahai Uplift of the Junggar Basin. The gas genetic types and sources of deep coalbed methane (CBM) in the Jurassic period of the Baijiahai Uplift are inconclusive. Based on the analysis of geochemical characteristics, maturity, natural gas composition, and carbon isotope of source rocks, combined with plate verification and seismic interpretation, the genetic types of deep CBM in Jurassic were identified, and the gas source and migration path of deep CBM in Jurassic were revealed. The results show that the three sets of source rocks of Carboniferous, Permian, and Jurassic in Baijiahai Uplift have good hydrocarbon potential. The organic matter types of Jurassic source rocks are mainly II₂ and III, and the evolution of organic matter is in the low-maturity stage. The deep CBM in Jurassic atoms is a mixed gas containing exogenous input gas. The coal-type gas is derived from the Carboniferous, Permian, and Jurassic humic kerogens, with an average proportion of 54.47%. The oil-type gas is derived from the Permian sapropelic kerogens, with an average proportion of 45.43%. In the plane, the closer to the fault, the greater the proportion of oil-type gas. The genetic types and gas sources of Jurassic deep CBM in the Baijiahai Uplift are clarified in this study area. The research results are helpful to deepen the understanding of the enrichment law of deep CBM and provide references for the optimization of favorable exploration areas.