LAUSR

Abstract The flow pattern, pressure drop gradient and apparent viscosity of extra heavy crude oil solution CO2 (viscosity = 10,821 mPa·s at 50 °C) were studied in the high-temperature and high-pressure experimental loop driven without pump shear. Based on the study of the dissolution characteristics of CO2 in extra heavy crude oil, combined with local sampling, micro-photographing and pressure drop gradient testing, three different flow patterns were identified. As the volume of solution CO2 increases, the flow pattern transition boundary gradually shifts to high pressure. In addition, due to the high viscosity of extra heavy crude oil, the flow pattern is relatively less affected by temperature and flow velocity. Pressure drop gradient was introduced to analyze the flow characteristics of extra heavy crude oil solution CO2. Comparing the pressure drop gradients of extra heavy crude oil solution CO2 under different conditions, it can be seen that the presence of CO2 in the dissolved state is better than the precipitation in the form of microbubbles for viscosity reduction of extra heavy crude oil. As soon as the system pressure drop is near the saturation pressure, pressure drop gradient is found to be the lowest. The foam quality concept was introduced to correlate with the apparent viscosity and viscosity reduction characteristics of the dispersion. The small particle size and large number of microbubbles contribute to the apparent viscosity reduction of the dispersion.