Rheology of Thickened 100% Liquid CO₂ Fracturing Fluid

A surfactant thickening agent suitable for use in dry-fracturing with liquid CO₂ has been developed.The thickening process of liquid CO₂ was simulated online through high pressure pipe flow rheological experiments.Results of the experiments have revealed that the surfactant forms rods or wormlike micelle in liquid CO₂,thereby increases the viscosity of the liquid CO₂ by 86-218 times of the original viscosity.The liquid CO₂ treated with the thickening agent has shear-thinning characteristics.Increase in pressure or increase in the volumetric fraction of the thickening agent has smaller effect on the viscosity and rheology of the thickened liquid CO₂ fracturing fluid,and the effective viscosity of the fracturing fluid decreases exponentially with increase in temperature.The thickened liquid CO₂ fracturing fluid has flow index that increases with increase in temperature,and consistency factor that decreases with increase in temperature.