川中—川南过渡带须家河组砂岩储层次生孔隙成因与分布特征

Distribution and Origin of Secondary Pores in Xujiahe Formation Sandstone Reservoirs in Mid-south Sichuan Basin

川中—川南过渡带须家河组岩石学特征表明,砂岩储集空间以原生残余粒间孔和次生孔隙为主。次生孔隙的成因主要是煤系地层中有机质成熟时释放的有机酸和成岩过程中有机质脱羧作用产生的CO2形成的酸性水对长石、岩屑、碳酸盐胶结物以及粘土矿物等的溶解。另外次生孔隙还与烃源岩的厚度及分布、砂体所处的沉积微相和断裂沟通有关。次生孔隙在垂向上发育2个次生孔隙带,主要分布在1 700~2 050 m深度范围内;平面上次生孔隙的分布主要受沉积物原始组分的影响。

The research of petrologic character in the mid-south Sichuan Basin indicates that reservoir spaces in Upper Triassic Xujiahe Formation are mainly crude residual intergranular pores and secondary pores.The origin of the secondary pores is the dissolution of feldspar,debris,carbonate cement and clay mineral by organic and carbonic acids,which are generated during the evolvement of organic material.Moreover,the secondary pores are related to the thickness and distribution of source rock,sedimentary microfacie...