A review of sandstone illite cements and aspects of their significance to hydrocarbon exploration and development

Current understanding of the origin of illite cements within the pore systems of sandstone reservoirs is at best speculative whilst knowledge of the control of illite morpholoy is, to all practical purposes, non‐existent. This is unfortunate considering the widespread occurrence of illite and the often disastrous decrease in reservoir performance associated with its presence (up to 200‐fold decreases in permeability have been recorded from aeolian sandstones of the U.K. southern North Sea for example). An advanced knowledge of the origin of this clay mineral is thus of considerable importance to the future of the hydrocarbon exploration and production industry. This paper presents an assessment of sandstone illite morphotypes and reviews the mechanisms which have been proposed for their formation.