Diagenetic evolution and source rock control of hydrocarbon in the Papua Basin

The differences in the distribution range, organic matter types, and thermal evolution of the Mesozoic and Cenozoic source rocks in the Papuan Basin result in differences in their oil and gas distribution. The results show that: ① Mesozoic source rocks were mainly developed in the northwest of the Papuan Basin. The Jurassic source rocks entered the high maturity stage in the eastern and western parts of the Papuan Fold Belt and the peak oil generation stage in the middle section of the Papuan fold belt and the Frye Platform, while the lower Cretaceous source rocks on the northern edge of the Papuan Fold Belt and Frye Platform entered the peak oil generation stage; ②The southeastern part of the basin was mainly developed with the Cenozoic source rocks, and the main hydrocarbon generation stoves are distributed mainly in the coastal shallow sea area of the Aure Depression. The Middle Miocene source rocks have the characteristics of late maturity and high maturity, while the Upper Miocene source rocks as a whole have not reached the mature stage; ③The Papuan Fold Belt is controlled quite clearly by the maturation and evolution of source rocks. The middle and western sections were mainly supplied by Jurassic source rocks, while the eastern section was supplied mainly by the Cretaceous source rocks. The eastern and western sections were continuously supplied by overlying high maturity source rocks, and both mature gas reservoirs and condensate gas reservoirs were developed. The Jurassic source rocks in the middle section were at the peak of oil generation, mainly consisting of type II kerogen and developing mainly normal oil reservoirs; ④The distribution of oil and gas in the Frye Platform and Papuan Bay was jointly controlled by the organic matter type and maturation evolution of the source rocks. The oil and gas source of the Frye Platform is a mixture of the Mesozoic source rocks, and the oil and gas type in its northern edge is similar to that in the central and western sections of the Papuan Fold Belt. The southern slope zone is also controlled by the organic matter type and maturation evolution of the source rocks. Oil and gas are mainly supplied by the Cretaceous source rocks; and in the Papuan Bay region, due to different hydrocarbon supply layers, there are differences in the types and maturation evolution of organic matter in source rocks, in which mature gas reservoirs and biogenic gas reservoirs in the Cenozoic. The main source of mature oil and gas is Middle Miocene source rocks, while the main source of biogenic gas are the Upper Miocene source rocks.