Preparation and Performance of Supercritical Carbon Dioxide Thickener

The low sand-carrying problem caused by the low viscosity of supercritical carbon dioxide (SC-CO₂) limits the development of supercritical CO₂ fracturing technology. In this study, a molecular simulation method was used to design a fluorine-free solvent-free SC-CO₂ thickener 1,3,5,7-tetramethylcyclotetrasiloxane (HBD). Simulations and experiments mutually confirm that HBD-1 and HBD-2 have excellent solubility in SC-CO₂. The apparent viscosity of SC-CO₂ after thickening was evaluated with a self-designed and assembled capillary viscometer. The results show that when the concentration of HBD-2 is 5 wt.% (305.15 K, 10 MPa), the viscosity of SC-CO₂ increases to 4.48 mPa·s. Combined with the capillary viscometer and core displacement device, the low damage of SC-CO₂ fracturing fluid to the formation was studied. This work solves the pollution problems of fluoropolymers and co-solvents to organisms and the environment and provides new ideas for the molecular design and research of SC-CO₂ thickeners.