Experimental investigation on rheological properties and friction performance of thickened CO2 fracturing fluid

• Rheological properties of thickened CO2 fracturing fluid were investigated.
• The correlations for rheological parameters were obtained.
• The effects of various factors on rheological properties were analyzed in detail.

For the purpose of guiding the field treatment of CO2 stimulation, the experimental investigation on rheological properties and friction performance of thickened CO2 fracturing fluid system is performed in the pressure range of 10–30 MPa and the temperature range of 0–100 °C by using high-parameter fracturing fluid test system. The correlations for thickened CO2 fracturing fluid rheological parameters have been obtained. The results present that the effective viscosity decreases with increasing shear rate and the change below 500 s−1 is more sharp. The effective viscosity decreases from 20 mPa s to 8.2 mPa s with increasing temperature at 20 MPa, 3.0 wt% and 393 s−1, and shows a small increase with increasing thickener concentration. Temperature and shear rate influences on the rheological properties are larger in various influencing factors. The frictional resistance coefficient of the thickened CO2 fracturing fluid decreases from 0.69 to 0.12 with increasing flow velocity at 20 MPa, 15 °C and 3.0 wt%, and levels off as the flow velocity reaches 0.4 m/s. The friction resistance coefficient presents a decrease trend with increasing temperature, and increases with increasing pressure or thickener concentration at the constant temperature, however, the change range is smaller.