The Study of the Diagenesis of the Lower Cretaceous, Niton Basal Quartz Sandstones of Western Alberta; with Specific Reference to the Porosity and Permeability Modification

Abstract

<p>Abnormal accumulations of kaolinite and illite clay minerals, significantly reducing reservoir potential in localized portions of the Niton Basal Quartz sandstones, have prompted a detailed examination of the (clay) mineralogy and diagenetic history of these sands. Scanning electron microscopy and thin section analysis show that the bulk of porosity reduction is by the accumulation of detrital clays in sands where insufficient winnowing has occurred during deposition in the deltaic environment. The progressive assemblage of authigenic quartz overgrowths, authigenic illite and authigenic kaolinite further reduce porosity and permeability during diagenesis. Secondary kaolinite tends to infill sands of high initial porosity. Oil migration occurs after the formation of authigenic kaolinite and minor amounts of dissolution porosity, Clay accumulations reduce but do not destroy reservoir potential of the Niton Basal Quartz sandstones.</p>