元坝地区须家河组砂岩成岩作用与孔隙演化

摘要

The sandstones in the Triassic Xujiahe Formation in Yuanba area are typical low-porosity and low-permeability reservoirs. The diagenesis and porosity evolution of sandstones as well as their influences on reservoir physical properties were studied by means of ordinary and casting thin section microscopic identification, SEM and X-ray diffraction. The main diagenetic effects included compaction/pressolution, cementation, replacement, corrosion and cracking, among which the compaction/pressolution, siliceous and carbonate cementation effects greatly reduced native sandstone porosities and destructed sandstone reservoirs, while the chlorite rim cementa-tion, corrosion and fracturing effects protected and improved reservoirs. At present, the sandstones in the Xujiahe Formation in Yuanba area have entered the middle diagenesis stage A, and partially in the middle diagenesis stage B.Most of the reservoir's primary porosities have been destroyed after severe diagenetic evolution, and the main pore types are secondary pores and associated cracks.%元坝地区上三叠统须家河组砂岩属于典型的低孔低渗型储层。通过显微镜下常规及铸体薄片鉴定、扫描电镜观察、X-衍射等手段，对研究区砂岩储层的成岩作用、孔隙演化及其对储集物性的影响进行了深入研究。研究区发育的成岩作用类型主要有压实作用、压溶作用、交代作用、胶结作用、溶蚀作用及破裂作用。其中破坏性成岩作用为压实压溶、硅质胶结和碳酸盐岩胶结作用；而绿泥石环边胶结、溶蚀和破裂作用则对储层起到了保护和改善作用。元坝地区须家河组砂岩目前已达中成岩阶段A期，一些地区已经达中成岩B期。储层经历强烈的成岩作用后原生孔隙基本被破坏，孔隙类型主要为次生孔隙并伴生裂缝。