全球前寒武系—下寒武统原生油气藏地质及分布特征

Geological characteristics and distribution of global primary hydrocarbon accumulations of Precambrian-Lower Cambrian

近年来,前寒武系—下寒武统原生油气资源在全球油气勘探领域越来越受重视。位于俄罗斯的东西伯利亚盆地、中东的阿曼盆地以及我国的四川盆地前寒武系—下寒武统的原生油气藏储量最为丰富。以这3个盆地为例,系统全面地阐释全球前寒武系—下寒武统原生油气藏的地质及其分布特征,以期为古老层系油气勘探的进一步突破提供参考。全球前寒武系—下寒武统原生油气藏油气探明和控制储量已达30090 MMboe(4.12×10^(8) t油当量),其中84.2%分布于东西伯利亚盆地,而阿曼盆地和四川盆地分别占8.9%和6.5%。烃源岩以海相泥页岩、碳酸盐岩为主,整体处于低熟—过熟阶段,且大部分分布于构造低部位;储集岩主要为碎屑岩和碳酸盐岩,早期白云岩化作用、表生淋滤作用和油气早期充注是古老碳酸盐岩储层发育的重要机制;深层和超深层古老层系的油气大部分储于碳酸盐岩中。同时,广泛发育的优质区域性盖层是油气得以有效保存的一个重要因素。自生自储成藏模式、源储相邻近源成藏模式和源储相隔“远”源成藏模式构成了前寒武系—下寒武统原生油气藏的主要成藏模式。

In recent years,primary hydrocarbon accumulations of Precambrian-Lower Cambrian have caused an increasing attention in the oil and gas explorations worldwide.The Eastern Siberian Basin in Russia,the Oman Basin in the Middle East,and the Sichuan Basin in China are endowed with the richest oil and gas reserves in the Precambrian-Lower Cambrian primary hydrocarbon accumulations.This study takes these three basins as examples to systematical and comprehensively document the geological characteristics and distribution of the global Precambrian-Lower Cambrian primary hydrocarbon accumulations through a large amount of data analysis and statistics,to provide insights for further breakthroughs of oil and gas explorations in ancient stratigraphic successions of sedimentary basins.The global proven and controlled reserves of Precambrian-Lower Cambrian primary hydrocarbon accumulations have reached 30.09×10^(9) boe(4.12×10^(8) t),of which 84.2% are distributed in the Eastern Siberian Basin,while the Oman Basin and the Sichuan Basin account for 8.9% and 6.5%,respectively.The source rocks are dominated by marine mudstones,shales and carbonate rocks,which are generally immature to over-mature and mostly distribute in low structural parts.Carbonate rocks and clastic rocks are important types of reservoir rocks.Early dolomitization,superficial leaching and hydrocarbons injection are important mechanisms for the development of ancient carbonate reservoirs.Most of the hydrocarbons in deep and ultra-deep ancient strata are stored in carbonate rocks.At the same time,the extensively developed high-quality regional caprocks are the key to preserving abundant hydrocarbons.Three types of accumulation models,self-generating and self-preserving,reservoirs adjacent to source rocks,and reservoirs isolated to source rocks,constitute the main models of Precambrian-Lower Cambrian primary hydrocarbon accumulations.