四川盆地南川地区娄山关群碳酸盐岩成岩作用研究

四川盆地南川地区中—上寒武统娄山关群储层主要为台地边缘滩沉积,以白云岩为主。主要成岩作用类型有:白云岩化、溶蚀、破裂、胶结充填及压实压溶作用,对储层形成有重要贡献的成岩作用是白云岩化作用、溶蚀作用及破裂作用。根据白云石标型特征、有序度、碳氧同位素的分析,认为娄山关群白云岩成因有3种:准同生、混合水以及埋藏白云岩化作用,以准同生白云岩化作用为主。储层发育3期溶蚀作用:大气淡水溶蚀、埋藏溶蚀和表生溶蚀,以表生溶蚀作用为主。白云岩化作用和表生溶蚀作用是形成优质储层的关键,而胶结、充填作用破坏了大量的原生和次生孔隙,不利于储层的发育。

Diagenesis of Middle and Upper Cambrian Loushanguan Group reservoirs in Nanchuan area,Sichuan Basin

The Middle and Upper Cambrian Loushanguan Group reservoirs in the Nanchuan area of the Sichuan Basin mainly consist of platform margin shoal sediments. The main lithology is dolomite. The main diagenesis effects include dolomitization, solution, structural disruption, consolidated fill, compaction and pressure solution, among which, the first three of these work as the key effects for reservoir formation. According to dolomite types, order degree and C, O isotope analyses, the dolomites in the study area developed from three diagenesis effects, including penecontemporaneous dolomitization, mixing water dolomitization and burial dolomitization, among which the penecontemporaneous dolomitization is dominant. The Loushanguan reservoirs have experienced three periods of dissolution, including the corrosion action of atmospheric fresh water, the deep burial solution and the hypergene dissolution, among which the hypergene dissolution is the main controlling factor. Dolomitization and hypergene dissolution contribute to high-quality reservoir formation in the Middle and Upper Cambrian Loushanguan Group. Cementation and filling effects destroy a large number of primary and secondary pores, which is unfavorable for reservoir formation.