Clay minerals in sandstone reservoirs: implications for "smart water" injection

Abstract

Clay minerals as ubuquitous in sandstone reservoirs, yet many of their effects are not well understood. This literature study examines the relationship between the most common clay minerals and smart water injection in sandstone reservoirs. Ion exchange capacities, wettability, and reservoir quality are examined as functions of origin, morphology, chemical properties, and particle size of clay minerals. Authigenic clay minerals are found to have severe consequences for reservoir quality, especially in deeply buried reservoirs. Diagenetic processes, like illitization and chlorite coating can reduce permeability and porosity to the point where production becomes impossible, while kaolinite can contribute to more favorable initial wetting conditions. Cation exchange capacity can vary significantly due to effects of particle size and pH, affecting adsorption/desorption of polar oil components, both in the reservoir and in core flood experiments. It will also be shown that fibrous clay morphologies, common for illites and smectites, collapse during air-drying, leaving core samples unrepresentable with regards to their native state. Steps such as critical point drying should be taken to preserve these morphologies when using core floods to simulate smart water injection. Further study of wetting properties related to morphology and isomorphous substitution, as well as more thorough characterizations of common hyllosilicates is suggested. The role of anionic exchange capacity in adsorption/desorption reactions for kaolinite and chlorite may also warrant a closer look.