川东涪陵地区中侏罗统凉高山组致密砂岩储层特征及成因

Characteristics and genesis of tight sandstone reservoirs of Middle Jurassic Lianggaoshan Formation in Fuling area,eastern Sichuan Basin

针对川东涪陵地区凉高山组砂岩储层孔隙类型多样、非均质性强、优质储层特征及成因机制研究薄弱的问题,应用铸体薄片、扫描电镜、压汞、核磁共振及岩心微米CT等手段,系统研究了凉高山组砂岩储层在微观孔喉结构、流体可动性、物性、成岩作用等方面的差异,建立了凉高山组砂岩储层分类评价标准,明确了优质储层成因及主控因素。结果表明:①凉高山组发育3类储层,I类储层压汞曲线为下凹型,储集空间为原生粒间孔、粒内溶孔,发育大孔一细喉结构,连通性好,流体可动性>30%,含油气饱和度>65%,是有利的勘探目标。②凉高山组河道砂岩储层为相控孔隙型储层,规模较大的主河道砂体厚度大,砂岩粒度粗,分选好,是优质储层发育的基础。③压实作用及碳酸盐胶结是储层致密化的主要原因,薄膜状绿泥石抑制硅质、碳酸盐胶结物生长,利于原生粒间孔隙、喉道保存,平面上靠近生烃中心、纵向上贴近烃源岩层的砂岩溶蚀作用强,储集空间得到进一步改善,研究成果为后续勘探部署提供了地质依据。

In view of the poor research about characteristics and genetic mechanisms of reservoirs in the Liang⁃gaoshan Formation sandstone reservoirs in the Fuling area,based on the application of thin sections,SEM,mercury injection,NMR,and micron CT,this paper has studied the differences in micro-pore throat structure,fluid mobility,physical properties,and diagenesis.The classification evaluation criteria for sandstone reservoirs have been established,the causes and main controlling factors have been clarified.(1)There are three types of the Lianggaoshan Formation reservoirs.The mercury injection curve of type I reservoirs is concave,with large pore-throat structure,reservoir space being primary intergranular pores and intragranular dissolved pores,with good connectivity,fluid mobility>30%,oil saturation>65%.(2)The channel sandstone reservoirs are fa⁃cies-controlled pore reservoirs with large-scale main channel sand bodies with thick sandstone grain size and good sorting.(3)Compaction and carbonate cementation are main reasons for reservoir densification,the filmlike chlorite inhibits the growth of silicious and carbonate cements,which is beneficial to pores and throats pres⁃ervation.The sandstone dissolution near the hydrocarbon generation center on the plane and close to the source rock layer in the vertical direction is strong,further improving the reservoir space.The research results provide a geological basis for the subsequent exploration deployment.