Research progress on supercritical CO2 thickeners

Abstract

According to the thickening principle and molecular structure of thickeners, supercritical carbon dioxide (scCO₂) thickeners have been summarized and introduced by dividing into polymers, small molecular compounds and surfactants. The properties such as solubility, thickening effect, thickening condition and existing problems of scCO₂ thickeners are analyzed and assessed, and the research progress and prospects of scCO₂ thickeners are proposed. ScCO₂ is used in both CO₂ fracturing and CO₂ flooding for enhanced oil recovery (EOR). However, due to its low viscosity, the proppant carrying ability and filtration control ability of scCO₂ are too weak for fracturing. Also, in the process of CO₂ flooding, its low viscosity not only exacerbates the gravity override but also leads to an unfavorable mobility ratio that results in viscous fingering, early breakthrough, and poor sweep efficiency. Therefore, scCO₂ thickeners have good application prospects in oil and gas production for improved oil recovery (IOR).