Illitization of Smectite in Sandstones: The Permian Unayzah Reservoir, Saudi Arabia

摘要

The transformation of smectite to illite through a mixed-layer illite/smectite is a major clay mineral reaction that occurs in a range of diagenetic environments and is commonly observed in siliciclastic sedimentary basins worldwide. This reaction is controlled by several chemical and physical factors. Two of the major controlling factors are temperature and potassium availability within the sediments. Illite coating in the Permian Unayzah reservoir has two main morphologies, platelet-like and fibrous illite. The former is interpreted as formed by transformation of infiltrated smectite during burial. The latter has likely been formed by precipitation from pore water.