东濮凹陷古近系深层次生孔隙垂向分布特征及成因

Vertical distribution and genesis of the secondary pore in deep formation of Paleogene at Dongpu Sag

从岩石铸体薄片、扫描电镜观察和碳酸盐含量、镜质体反射率、黏土矿物分析及物性数据发现，长石、碳酸盐和硫酸盐等酸性组分的溶蚀是东濮凹陷古近系储集层次生孔隙形成的主导因素，且随埋深增大，碳酸盐溶蚀程度减小，长石溶蚀程度增加。次生孔隙有粒间溶孔、粒内溶孔、胶结物溶孔、铸模孔以及裂缝（隙）等。垂向上从上至下，对应深度2375～2675m、2975～3350m、3675～4200m和4500m以下依次发育4个次生孔隙带，其主要形成机理有：有机质热演化过程中产生的酸性流体的溶解作用；异常高压环境中的热循环对流、幕式排烃以及异常高压导致的生油窗扩展作用；不整合面和断裂带附近的淋滤作用等。

Through the analyses of various data, including thin section analysis, SEM, carbonate content, reflectance of vitrinite, clay, reservoir property and others, it is found that the corrosion of the acidic compositions of feldspar, carbonate, sulfate, etc. , is the key factor for the generation of reservoir secondary pores. With burial depth, the corrosion degree of carbonate decreases and that of feldspar increases. The main types of the secondary pores are intergranular pores, intragranular dissolved pores, cement dissolved pores, moldic pores, and fractures. Vertically, there are four secondary pore systems distributed in the formations from 2375m to 2675m, from 2975m to 3350m, from 3675m to 4200m, and below 4500m. The mechanisms of genesis include： thermal evolution of organic matter, experiments indicate that the thermal degradation makes kerogen produce a large amount of organic acid before it goes into the oil generation windows; abnormally high fluid pressure, the fluid thermal cycle convection and curtain-draining hydrocarbon will enlarge oilgeneration windows and lead to the forming of secondary pores; eluviations at unconformities or fracture zones produce weathered crust secondary pores.