Influence of crystallographic habit and aggregate structure of authigenic clay minerals on sandstone permeability

Abstract

Our studies have shown that shifts in the trend of the permeability/porosity relationship for sandstones may be explained in terms of the crystallographic habit and aggregate structure of authigenic clay minerals. It is also suggested that the specific surface (surface/volume ratio) of the clay minerals (either authigenic or detrital in sandstones) could account quantitatively for the different permeability/porosity relationships and might represent a parameter that could be introduced into conventional permeability/porosity plots. It is assumed that a high specific surface of the interstitial clay minerals will induce tortuosity and therefore turbulence at higher flow rates and will also cause pore-space reduction by favouring water adsorption on the large available clay-mineral surface. The thread-like habit often observed for authigenic illite will also cause a division of pore space into a large number of tiny holes, through which fluid flow is much more difficult.