松辽盆地古龙页岩岩性、物性、含油性特征及控制因素

Lithology,physical property,oil-bearing property and their controlling factors of Gulong shale in Songliao Basin

松辽盆地北部古龙页岩油为源储一体型非常规资源,但古龙页岩的岩性、物性、含油性均存在明显的非均质性。为了揭示含油性、储集性特征及其控制因素,通过薄片鉴定、场发射扫描电镜、热解色谱及激光共聚焦三维重建等技术方法,利用孔隙度、镜质体反射率、有机碳等参数,分析对比了研究区东西向、南北向剖面青山口组页岩的岩性、物性、含油性特征。结果表明:古龙页岩由石英、黏土矿物、长石、白云石等矿物组成,主要包括页岩、粉砂质页岩、粉砂岩、泥—粉晶云岩、介屑灰岩5种岩石类型,其中页岩、粉砂质页岩为有利岩性组合;有机质演化程度和成岩作用类型控制孔隙发育,有机质热演化过程中形成大量有机孔、溶蚀孔,随着成岩转化作用的增强,黏土矿物晶间孔缝发育并形成页理缝,连通了基质孔隙,构成规模聚集的储集空间和渗流通道;埋深大、有机碳含量高的页岩层具有极好的含油性,油气主要聚集于基质孔隙和页理缝中,有机碳和成熟度协同控制页岩油丰度,不同岩石类型导致的储集物性差异是控制同层位含油性非均质性的关键因素。页岩岩性、物性、含油性特征的厘定,为古龙页岩油分类评价标准的建立及勘探目标层段的优选提供了可靠依据。

Gulong shale oil in the north of Songliao Basin is“source-reservoir-one-layer”unconventional resource,but with obvious heterogeneity in lithology,physical property and oil-bearing property of the shale.In order to reveal oil-bearing and reservoir properties and their controlling factors,techniques of thin section identification,FESEM,pyrolysis chromatography and laser confocal 3D reconstruction are used based on parameters of porosity,vitrinite reflectance and TOC to perform comparative study on lithology,physical property and oil-bearing property of Qingshankou Formation shale in studied area in E-W and S-N sections.The results show that Gulong shale is composed of minerals of quartz,clay minerals,feldspar,and dolomite,with mainly 5 rock types including shale,silty shale,siltstone,muddy-silty dolomite and shell clastic limestone,of which the shale and silty shale are favorable lithologic assemblages.Organic matter evolution degree and diagenesis type control the development of pores.Large amount of organic matter-hosted pores and dissolution pores formed during thermal evolution of organic matter.With enhancement of diagenetic transformation,intercrystalline pores of clay minerals developed and lamellation fractures formed,connecting matrix pores and formed large-scale accumulation space and flow channel.Shale layer with large burial depth and high TOC has excellent oil-bearing property,with oil and gas mainly accumulated in matrix pores and lamellation fractures.Shale oil abundance is controlled by both abundance and maturity of organic matter.Difference of reservoir physical property caused by different rock types is the key factor to control the heterogeneity of oil-bearing property in the same layer.Determination of shale lithology,physical property and oil-bearing property provides reliable evidences for establishment of Gulong shale oil classification and evaluation criteria and optimization of exploration target intervals.