Multi-component hydrocarbon-generation patterns and geological significance of the Permian Pusige Formation source rocks in the piedmont of southwestern Tarim Basin, NW China

The traditional binary hydrocarbon-generation patterns are inadequate for accurately evaluating the hydrocarbon- generation potential of different types of source rocks in the Permian Pusige Formation in the piedmont of southwestern Tarim Basin, especially the resource potential of light oil and condensate. We selected the Pusige Formation source rocks from the piedmont of southwestern Tarim Basin to conduct closed gold tube pyrolysis experiments, recovered the hydrocarbon-generation process under geological conditions using the method of hydrocarbon-generation kinetics, and established multi-component hydrocarbon-generation patterns of source rocks with three quality levels. The results show that the total hydrocarbon yields of good (TOC = 1.35%), fair (TOC = 0.70%), and poor (TOC = 0.24%) source rocks are 648, 236 and 108 mg/g, respectively. The good source rock shows more concentrate oil-generation process, while fair source rock has stronger dry gas potential at the high-maturity stage. Furthermore, based on the characteristics of hydrocarbon generation of the Pusige Formation source rocks, the formation and evolution of oil and gas can be divided into the immature, and heavy hydrocarbon, light hydrocarbon, wet gas, and dry gas generation stages. The proposed multi-component hydrocarbon-generation patterns are used to evaluate the hydrocarbon-generation potential and resources of different reservoirs. The resources of heavy oil, light oil, wet gas, and dry gas generated by the Pusige Formation source rocks in the study area are estimated to be 225×10 8 t, 150×10 8 t, 3×10 12 m 3 and 6×10 12 m 3 , respectively. The Pusige Formation source rocks in the piedmont of southwestern Tarim Basin exhibit great hydrocarbon-generation potential, providing the material foundation for forming large oil and gas fields. This area rich in light resources is promising for future petroleum exploration, and it is expected to become a national resource strategic base in China.