Experimental Study on Rheological Properties of Thinkened Co2 in Liquid and Supercritical State

The rheology of CO2 fracturing fluid are complicated because of its phase change. In this work, pipeline rheology of CO2 in a range of 8–16 MPa and 10–60 °C were studied. The results showed that the thickened CO2 was characterized by a power-law fluid. With the thickener or pressure increased, the consistency coefficient K increased and the flow index n decreased. In the liquid or supercritical state, temperature increasing made the K decrease and the n increase. However, when CO2 transformed from the liquid to the supercritical state in 30–40 °C, and the K increased while the n decreased.