Chemometric differentiation of natural gas types in the northwestern Junggar Basin, NW China

Abstract

In recent years, the natural gas has displayed a growing significance in oil and gas exploration in the northwestern Junggar Basin (NWJB), although oil has been the main focus of exploration in the basin. Here, we systematically discuss the classification and origin of the natural gases from the NWJB based on the natural gas geochemistry and chemometric methods. The natural gases collected from the NWJB were chemometrically classified into three groups. Group A gases, defined as coal-derived gases, were likely generated from the mixing of the Jiamuhe Formation and Carboniferous strata. Group B gases, defined as the mixing of coal-derived and oil-associated gases, were restricted to the source rocks of group A and C gases. Group C gases, defined as oil-associated gases, were likely derived from both the Fengcheng and Wuerhe Formations, with a higher contribution from the latter strata. The result of this study suggests that the potential of oil generation in the Wuerhe Formation has been underestimated in the past. This is in accordance with geochemical and geological evidence. This study provides an effective chemometric method of natural gas classification and evaluation of hydrocarbon generation potential. This contributes to a better understanding of the origin of gases and distribution of oil and gas, assisting in exploration deployment in the basin.