Development status of supercritical carbon dioxide thickeners in oil and gas production: A review and prospects

In recent years, the continuous advancement of supercritical carbon dioxide (sc CO2) in the field of oil and gas production has highlighted the increasingly undeniable challenges posed by low viscosity. Issues such as gravity override, viscous fingering, and poor sand-carrying capacity have become more prominent. The introduction of SC-CO2 thickeners stands as a promising solution to address current challenges. Despite over fifty years of history in the design of supercritical carbon dioxide (sc CO2) thickeners, there is still no effective SC-CO2 thickener that can be widely applied in the field. Therefore, the future development of supercritical carbon dioxide (sc CO2) thickeners remains a topic of significant research interest. This paper reviews the current status, thickening mechanisms, and detailed thickening results of supercritical carbon dioxide (sc CO2) thickeners. Special emphasis is placed on the crucial role of thickeners in controlling the flow properties of SC-CO2, their practical applications, challenges, and future research directions. The exceptional thickening performance of a novel copolymer and surfactant system incorporating in-situ nanoparticles has been demonstrated. These options present promising choices in both direct and indirect thickeners for supercritical carbon dioxide applications.