川中地区中—下侏罗统砂岩储层特征

CHARACTERISTICS OF SANDSTONE RESERVOIRS OF MIDDLE-LOWER JURASSIC IN CENTRAL SICHUAN AREA

四川盆地川中地区中—下侏罗统砂岩储层的岩相-岩性特征主要受不同方向和沉积期物源控制,表现出了时空的继承性和分异性;成岩作用特征表现为强烈的压实作用,胶结、交代作用相对较弱,溶蚀作用主要发育于下沙溪庙组。储集空间类型多样,珍珠冲组和凉上段储层以剩余原生孔隙为主,川中东北部下沙溪庙组一、二段以浊沸石溶孔及长石颗粒溶孔为主;储层物性及孔隙结构显示了典型的特低孔、特低渗储层特征,垂向上以下沙溪庙组一、二段砂岩物性相对较好,平面上表现为泥质含量越低、粒度越粗,物性越好;储层分布特征揭示了储层发育受沉积物源、沉积相和成岩作用共同控制。

In this paper,a systematic discussion is given on the basic characteristics of Middle-lower Jurassic sandstone reservoirs in central Sichuan area,Sichuan Basin.Lithofacies and lithology of the sandstones,which are controlled by sedimentary source with different directions and difference episodes,have succession and difference temporally and spatially.Sandstone diagenesis is characterized by strong compaction,weak cementation and replacement,and dissolution is mainly developed in Xiashaximiao Formation.Accumunative spaces in Zhenzhuchong Formation and upper member of Lianggaoshan Formation are residual intergranular pores,while in members 1 and 2 of Xiashaximiao Formation in northestern Central Sichuan,accumulative spaces are mainly solution pores of laumontite cements and feldspar grains.Based on physical property and pore structure,the sandstone reservoirs are defined as ultra-low porosity and ultra-low permeability ones.Vertically,the members 1 and 2 of Xiashaximiao Formation are of highest quality.Horizontally,the lower of the clay content is,the coarser the grain size,the better reservoir quality.Distribution characteristics reflect that reservoir properties are controlled by provenance,despositional facies and diagenesis.