Geochemical Characteristics And Reservoir Formation Evolution Of Puguang Gas Pool, Northeast Sichuan Basin, China

Puguang Gas Field structure is a nose-shaped structure, which locates at Shuangshimiao-Puguang NE structural belt to the northeast fold-fault belt of the east of Sichuan Basin, between Daba mountain fold-fault belt of thrust block front and Chuanzhong flattened fold belt. The whole is a southwest higher, northeast lower, west wing steeper, east wing smoother, in connection with thrust fault, NNE strike, large long axis fault-anticline structure. The west of the structure is controlled by NE strike thrust fault, the north and the east are controlled by structural line, and the south is controlled by sedimentary facies change belt. It is a structure-lithology trap which is controlled by structure and facies change line. The trap characteristics is similar with Dukouhe gas pool and Luojiazhai gas pool. Puguang gas pool is low temperature, constant pressure and high H₂S. By means of hydrocarbon source rocks generating hydrocarbon condiyion and thermal evolution analysis, the study of reservoir bitumen characteristics and origin, the study of gas geochemical characteristics and origin, trap evolution history analysis and hydrocarbon evolution history analysis, the author makes the following understanding:(1)Silurian system hydrocarbon source rock began to generate hydrocarbon after early Triassic sediment, oil generatin peak in early middle Jurassic, vitrinite reflectance 1.5% after middle middle Jurassic sediment, about 40Ma in the stage of mature. Then its vitrinite reflectance was 2.0% quickly in latter middle Jurassic, and it was about 30Ma in the stage of high mature. It generated dry gas when it was post mature in latter middle Jurassic. And its maximum buried depth was about 9600m in latter early Cretaceous. Permian system hydrocarbon source rock began to generate hydrocarbon about in late Triassic, oil generatin peak in middle middle Jurassic. It was at the stage of high mature in early late Jurassic, post mature from latter late Jurassic to nowadays. Its evolution process is similar to Silurian system hydrocarbon source rock's, and its maximum buried depth was about 8300m in latter early Cretaceous. Silurian system and Permian system hydrocarbon source rocks generated dry gas when they were post mature after late Jurassic.(2)There are reservoir bitumens in Ziliujing, Xujiahe, Feixianguan and Changxing formation in Puguang gas pool, especially feiyi and feier main reservoirs. These reservoir bitumens are...