世界深水含油气盆地烃源岩的发育特征及对中国南海北部深水区烃源岩的启示

The development characteristics of source rocks in the main deepwater petroliferous basins of the world and their enlightenment to the study of source rocks in deep-water area of northern South China Sea

国外深水盆地烃源岩发育特征表明:无论是板内的断坳盆地还是板缘的先裂陷后漂移沉积盆地,在裂陷期(断陷期)及坳陷期(漂移期)均有烃源岩分布,大陆边缘盆地不同演化阶段有效烃源岩发育程度存在差别,其中裂陷期非海相(湖相)暗色页岩是最主要和最普遍的生油岩,还可能发育过渡相或近海相的煤系和泥质烃源岩;其次是板内坳陷晚期或板缘漂移期的海陆过渡相、近海相、前三角洲相等有大量的有机质供给或者长期离物源区较近的情况下,烃源岩发育;裂陷晚期和坳陷早期烃源岩一般不发育,但有大量的有机质供给的半封闭浅海—半深海环境可能发育高效烃源岩。国外主要深水盆地中新生界烃源岩发育特征对中国南海北部深水区烃源岩的认识具有重要的指导意义。中国南海北部裂陷早期阶段发育的湖相烃源岩和裂陷晚期发育的海陆过渡相烃源岩为主力烃源岩;南海北部不同盆地坳陷期中新统海相烃源岩差异较大,其中陆源有机质输入不足的琼东南盆地烃源岩稍差些,陆源有机质输入相对充足的珠江口盆地烃源岩较好一些。墨西哥湾和北苏门答腊盆地的勘探实践已经证实了半深海相烃源岩可作为有效油源岩,这对中国南海北部深水区中新统海相烃源岩认识具有很好的借鉴意义。

The developmental characteristics of hydrocarbon source rocks in deepwater basins abroad show that hydrocarbon source rocks are distributed at the stage of firing and depression in both rifting- depressing or tiring- drifting basins. Effective source rocks have different development characteristics at different evolution stages of continental margin basin; of these rocks, non- marine （lacustrine） dark shale at the stage of tiring is the main and most common source rock. It is also possible to develop coal measures and muddy source rocks of transitional facies and paralic facies. With the supply of large quantities of organic matter of marine-continental transitional facies, paralic facies and prodelta facies at the late intraplate depression and under the margin-plate drifting condition, or in the circumstance of being long close to provenance, hydrocarbon source rocks would develop well. Source rocks do not develop at the late stage of tiring and the early stage of depressing. As a matter of fact, effective source rocks may develop under the condition of the supply of large quantities of organic matter from the semi- closed shallow sea and bathyal environment. The above characteristics have important guiding significance for the development of source rocks in northern South China Sea, where the main source rocks are lacustrine source rocks at the early tiring stage and marine-continental transitional facies source rocks at the late stage of tiring. Miocene marine source rocks vary in different basins. With enough terrestrial organic matter supply, source rocks from the Peal River Mouth basin is more effective than those from the Qiongdongnan basin. The exploration of Gulf of Mexico basin and northern Sumatra basin has proved that source rocks of bathyal facies seem to be effective source rocks, and this finding is of reference significance for the study of Miocene marine source rocks in northern South China Sea.