Preparation and Performance of Supercritical Carbon Dioxide Thickener

The low sand-carrying problem caused by the low viscosity of supercritical carbon dioxide (SC–CO(2)) limits the development of supercritical CO(2) fracturing technology. In this study, a molecular simulation method was used to design a fluorine-free solvent-free SC–CO(2) thickener 1,3,5,7-tetramethylcyclotetrasiloxane (HBD). Simulations and experiments mutually confirm that HBD-1 and HBD-2 have excellent solubility in SC–CO(2). The apparent viscosity of SC–CO(2) 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–CO(2) increases to 4.48 mPa·s. Combined with the capillary viscometer and core displacement device, the low damage of SC–CO(2) 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–CO(2) thickeners.