Wettability of rock minerals and the underlying surface forces: A review of the implications for oil recovery and geological storage of CO2

Abstract

The wettability of subsurface minerals is a critical factor influencing the pore-scale displacement of fluids in underground reservoirs. As such, it plays a key role in hydrocarbon production and greenhouse gas geo-sequestration. We present a comprehensive and critical review of the current state of knowledge on the intermolecular forces governing wettability of rock minerals most relevant to subsurface fluid storage and recovery. In this review we first provide a detailed summary of the available data, both experimental and theoretical, from the perspective of the fundamental intermolecular and surface forces, specifically considering the roles played by the surface chemistry, fluid properties, as well as other significant factors. We subsequently offer an analysis of the effects of chemical additives such as surfactants and nanoparticles that have emerged as viable means for manipulating wettability. In each example, we highlight the practical implications for hydrocarbon production and CO₂ geo-storage as two of the most important current applications. As the physico-chemical mechanisms governing the wetting phenomena are the main focus, special emphasis is placed on nano-scale experimental approaches along with atomic-scale modeling that specifically probe the underlying intermolecular and surface forces. Lastly, we discuss the gaps in the current state of knowledge and outline future research directions to further our fundamental understanding of the interactions and their impact on the wetting characteristics of Earth's minerals.