龙马溪组烃源岩对川中地区长兴组天然气成藏的贡献:来自华蓥山沥青抽提物生物标志化合物的证据OA

In order to clarify whether the Lower Silurian Longmaxi Formation source rocks have contributed to the Upper Permian Changxing Formation gas reservoirs in the central Sichuan Basin,gas chromatography-mass spectrometry(GC-MS)tests were conducted on source rocks from the Longmaxi Formation,Middle Permian Maokou Formation,and Upper Permian Longtan Formation,as well as solid bitumen from the Changxing Formation in the Jianshuigou section of the Huayingshan area.The source of solid bitumen in the Changxing Formation was identified to verify the contribution of Longmaxi Formation source rocks to Changxing Formation gas reservoirs.The following results are obtained.(i)The Longmaxi Formation source rocks are deposited in the lowest salinity water body,showing relatively high organic matter contribution from red algae;the Maokou Formation source rocks are deposited in the highest salinity water body,with green algae being an important hydrocarbon-generating parent material;whereas the Longtan Formation source rocks are deposited in water body with moderate salinity,with organic matter mainly supplied from red algae,green algae,and higher plants.(ii)The Changxing Formation solid bitumen in the Jianshuigou section of the Huayingshan area is of thermochemical alteration origin,primarily derived from the Longmaxi Formation source rocks.(iii)Deep-seated faults serve as favorable vertical migration pathways for deep hydrocarbons,enabling the transport of hydrocarbons generated by the Longmaxi Formation source rocks to the Changxing Formation for accumulation.It is concluded that the deep-seated faults can transport the hydrocarbons generated by the Longmaxi Formation source rocks to the Changxing Formation for accumulation.Eastern margin of the Mianyang-Guang'an shallow-water shelf,where deep-seated faults extending into the Changxing Formation are developed and the Longmaxi Formation source rocks are of high quality,is conducive to gas accumulation.Therefore,the exploration potential of Changxing Formation gas reservoirs deserves attention.