湖相烃源岩中的火山—热液深源物质与油气生成耦合关系研究进展

Progress on coupling relationship between volcanic and hydrothermal-originated sediments and hydrocarbon generation in lacustrine source rocks

陆内湖相烃源岩系是中国含油气盆地广泛发育的一类组分复杂且富含有机质的细粒沉积岩。随着非常规油气资源需求量日益增加,该岩系被作为致密油或页岩油层系受到广泛关注。然而,其极细的粒度增加了精细岩石学、矿物学研究难度,使它长期被简单视为陆源沉积岩。研究发现,该岩系中发育丰富的火山喷发及热液喷流产生的深源物质,并与油气的生成和富集表现出了极强的耦合关系。因此,探索深源物质如何参与烃源岩形成并影响油气生成亟待深入研究。作者详细总结并探讨了国内外近年来关于湖相烃源岩成因以及火山—热液活动带来的深源物质与油气形成关系的现阶段新发现与认识。并结合笔者研究团队基于新疆三塘湖盆地二叠系芦草沟组烃源岩的新发现,采用精细的岩石学、矿物学方法,结合无机和有机地球化学等方法,初步开展了该耦合关系的机理研究。认为火山—热液深源物质参与了烃源岩的沉积与成岩作用,并与正常湖相沉积物共同影响着油气的形成。建议重新认识湖相烃源岩的物质组成,从而拓展陆相生油理论,同时为同类型非常规油气资源勘探开发提供理论指导。

Intracontinental lacustrine source rocks are hydrocarbon-rich fine-grained sedimentary rocks with complex mineral compositions,which are widely distributed in Chinese petroliferous basins.The rocks are important unconventional oil and gas reservoirs amid increasingly demand for unconventional hydrocarbon resources.However,they have been mis-understood as simple terrestrial sedimentary rocks for a long time because the great difficulties in petrological and mineralogical research caused by their finegrained size.Recent studies found abundant sediments generated by volcanic eruption and hydrothermal exhalation in this type of source rocks;the sediments show a significant control on hydrocarbon generation and accumulation.Hence,the mechanisms and controlling factors of volcanic-hydrothermal sediments in hydrocarbon generation of this type of source rocks require in-depth studies.This paper summarizes and discusses recent research status on some new discoveries and viewpoints on the relationship between volcanic and hydrothermal-originated sediments and hydrocarbon formation.The connotation of the coupling relationship was preliminarily studied using detailed petrological and mineralogical as well as inorganic and organic geochemical data,on the basis of our new viewpoints on source rocks in the Permian Lucaogou Formation in Santanghu Basin.The volcanic and hydrothermal-originated sediments not only have played a significant role in deposition and diagenesis of the source rocks,but also show a co-influence on hydrocarbon generation and accumulation with conventional lacustrine sediments.We suggest that the mineral and lithological features of lacustrine source rocks should be re-studied.The result will expand the theory of hydrocarbon generation in terrestrial sediments and,practically,serve as a guide for unconventional hydrocarbon exploration of similar source rocks.