川西北地区海相油气成藏物质基础——优质烃源岩

BASIC CONDITIONS OF MARINE HYDROCARBON ACCUMULATION IN NORTHWEST SICHUAN BASIN——HIGH GUALITY SOURCE ROCKS

川西海相油气勘探程度低,油气成藏条件研究薄弱。通过区域地质、烃源岩形成环境、有机地化和有机岩石学等综合研究,重点探讨了龙门山构造带北段海相优质烃源岩发育情况。龙门山北段海相油气成藏的烃源条件好,主要有筇竹寺组、大隆组优质泥质烃源岩和栖霞组、茅口组优质碳酸盐岩烃源岩,而泥盆系烃源岩分布有限,奥陶纪—志留纪缺乏优质烃源岩形成条件。该区经历过大规模油气运移、聚集成藏和后期破坏过程,分析这一过程对川西海相油气勘探具有借鉴意义。预测龙门山逆冲推覆构造带和川西坳陷深处具有良好的海相油气勘探前景。

The prospecting degree of oil and gas is low and basic research about conditions of hydrocarbon accumulation is weak. Based on comprehensive study of regional geology, conditions of hydrocarbon formation, organic geochemistry and petrology, the developmental conditions of marine hydrocarbon in the north sector of Longmenshan structural belt were discussed. There were fair source rocks for hydrocarbon generation, mainly including muddy source rocks of Qiongzhusi and Dalong Formations and carbo- nate source rocks of Qixia and Maokou Formations. But the Devonian source rocks were limited in terms of their distribution. There was no qualified source rocks in the Ordovieian--Silurian. It underwent large scale of hydrocarbon migration, accumulation and late destruction in the Longmenshan belt. Analysis of this process may be helpful for marine petroleum exploration. Based on geological data, it was predicted that there were favorable target zones with better exploration prospects in the thrust-nappe tectonic belt and deepest depression of the northwest Siehuan Basin.