陆相超细粒页岩油储层沉积机制与地质评价

Deposition mechanism and geological assessment of continental ultrafine-grained shale oil reservoirs

超细粒(粒径<10μm)沉积储层中蕴含有50%以上的页岩油资源,是页岩油产量二次增长的重要领域,但当前对其成因机制和地质评价方法认识不清,制约了页岩油勘探开发突破。综合利用中国主要陆相页岩油盆地资料,厘定超细粒沉积岩的形成机制,按照其物质来源将超细粒沉积物划分为陆源型、内源型、热液-火山来源型、混合来源型4类,结合沉积动力和物质组分细分为陆源静水沉积型、陆源事件沉积型、内源生物残骸沉积型、内源生物化学沉积型、内源蒸发化学沉积型、火山空落沉积型、水底热液-火山喷发沉积型、混源静水沉积型、混源事件沉积型9种成因类型。系统分析了9类超细粒沉积岩储层特征的差异性,发现不同成因超细粒沉积岩的有机质丰度、含油性、脆性、孔渗性等储层质量参数差异明显,其中,内源生物残骸型和生物化学沉积型、部分热液-火山沉积型和混源静水沉积型超细粒沉积岩为优质页岩油储层,其页岩油储集潜力较大,是超细粒页岩油储层勘探中应重点关注的岩石类型。

The shale oil enriched in ultrafine-grained sendimentary rocks(grain size<10μm)account for more than 50%of the total shale oil resources;however,there is still a lack of clear understanding of its genetic mechanism and geological assessment methods,thus restricting the breakthrough in shale oil exploration and development.Therefore,the formation mechanism of ultrafine-grained sedimentary rocks was explored based on analyzing the data of shale oil-rich continental basin;according to the material source of ultrafine-grained sediments,the ultrafine-grained sedimentary rocks were divided into four types dominated by terrestrial source,intra-source,hydrothermal-volcanic source and hybrid source rocks;according to the sedimentary dynamics and material composition,they were further subdivided into nine genetic mechanisms,including terrestrial-sourced still water deposition,terrestrial-sourced event deposition,intra-source dead creature deposition,intra-source biochemistry deposition,intra-source evaporation-chemistry deposition,volcanic deposition,subaqueous hydrothermal-volcanic eruption deposition,hybrid-source still water deposition and hybrid-source event deposition.The ultrafine-grained sedimentary rocks of different genetic mechanisms vary significantly in reservoir quality parameters,such as organic matter abundance,oil content,brittleness and reservoir physical properties.Specifically,the ultrafine-grained sedimentary rocks dominated by intra-source dead creature deposition,intra-source biochemistry deposition,partial hydrothermal-volcanic deposition and hybrid-source still water deposition possess good shale oil reservoir potential,as being the important sweet spots of shale oil exploration.