燕山构造带东段中生界盆地页岩油气地质研究现状与展望

Shale oil and gas in the Mesozoic Basins,eastern Yanshan Orogenic Belt—exploration status and outlooks

中国陆相盆地页岩油资源丰富,是我国未来油气增储上产的重要战略接替领域。燕山构造带东段(辽西地区)中生界盆地群页岩油气资源丰富,但尚处于油气勘探空白区,落实其勘探前景势成必然。基于研究区勘探的实际情况,并通过与国内外典型页岩油气盆地石油地质条件对比,综合沉积体系以及烃源岩地球化学参数分析等,明确了燕山构造带东段中生界盆地群页岩油气的资源潜力。研究结果表明:(1)下侏罗统北票组和下白垩统九佛堂组均发育连续厚层的暗色泥页岩,为主力烃源岩层位;(2)烃源岩的总有机碳(TOC)含量均值为1%~4%,以Ⅱ_(1)型或Ⅱ_(2)干酪根为主,且指示热演化成熟度的镜质体反射率(Ro)普遍高于0.6%,具有良好的油气潜力;(3)两套烃源岩层系均富含火山碎屑成分,脆性矿物含量较高,具有良好的可改造性。针对陆相含油气盆地页岩油气勘探存在的问题,首先讨论了赋存页岩油气重要载体的碳酸盐质细粒沉积岩的多源成因机制与油气富集类型,其中研究区以火山热液型和混源型甜点为主;另外探讨了火山-湖泊作用对有机质的富集效应,认为火山灰的输入提升了有机质的富集效力。同时,根据以往的勘探实践经验,提出原型盆地恢复技术和“天-地-钻”三位一体技术是解决复杂造山带油气勘探(特别是密植山区)中面临的诸多问题的关键。

Continental basins in China possess abundant shale oil and gas resources and are an important strategic successor area for increasing oil and gas reserves and production in the future.The Mesozoic basin group in the eastern section of the Yanshan Orogenic Belt(western Liaoning)has rich yet unexplored shale oil and gas resources,therefore,petroleum prospecting in this area has become inevitable.Through field exploration and comparisons of basin’s geological conditions with that of typical domestic and foreign shale oil and gas basins,combined with comprehensive analysis of geochemical parameters for sedimentary systems and source rocks of the area,the shale oil and gas resource potential of the Mesozoic basin group is evaluated.The results show that(1)the Beipiao Formation of the Lower Jurassic and the Jiufotang Formation of the Lower Cretaceous are the main source rocks,with the extensive developments of thick and dark shales.(2)The source rocks are dominated by typeⅡ_(1)/Ⅱ_(2) kerogen;their total organic carbon(TOC)content is 1%-4%on average,and vitrinite reflectance(Ro),an indicator of source rock thermal maturity,is generally higher than 0.6%,indicating good petroleum generation potential.(3)The two sets of source rocks are both rich in volcanic clastic components,with high content of brittle minerals,and have good transformability.In view of the problems in shale oil and gas exploration in continental petroliferous basins,the multi-source genetic mechanism and oil and gas enrichment types of carbonate fine-grained sedimentary rocks,an important carrier of shale oil and gas,are first discussed,which suggests that volcanic hydrothermal fluids and mixed-source“sweet spot”are the main enrichment types in the study area;then the enrichment effect of volcano-lake interaction on organic matter is discussed,which indicates the volcanic ash input enhances the enrichment efficiency of organic matter.Meanwhile,based on previous exploration experience,it is proposed that the prototype basin restoration technology and the“space-earth-drilling”trinity technology are the key to solving many problems in the oil and gas exploration of complex orogenic belts(especially densely planted mountainous areas).