Experimental investigation on flow patterns and pressure gradients of shale oil-water flow in a horizontal pipe

With the growing demand for hydrocarbon resources and the depletion of conventional oil and gas reservoirs, the development of shale oil will become popular. As the shale oil fields gradually enter the middle and late stages of exploitation, the water content reaches as high as 60–80%. Analyzing the flow characteristics of shale oil-water flow during high water content can help optimize the range of flow parameters and improve pipeline transportation efficiency. However, research on shale oil-water flow patterns and pressure drop prediction models is still lacking. Therefore, this work conducted shale oil-water flow experiments in the multi-test section pipe flow loop, considering the temperatures (40–70°C), mixture velocity (0.2–1.2 m/s), and water contents (60–80%). The flow patterns of shale oil-water flow are studied, and the flow pattern maps are created. Moreover, the influence factors on pressure gradient are analyzed, including pipe diameter, water content, mixture velocity, and temperature. Eventually, the pressure drop prediction models are modified based on the pressure gradient and holdup experimental data. The results show that a thin oil film and an oil-sticking layer are adhered to the pipe wall at 40°C and 50°C, respectively. The mixture velocity increased from 0.4 m/s to 1.2 m/s, and the pressure gradient increased by 69.89% when the temperature and water content are constant. The lubrication coefficient is introduced in stratified flow (ST) and three-phase stratified flow (TPS) models, and the pipe flow friction coefficient is modified in dispersed flow (DF) and intermittent flow (IF) models. Moreover, the average relative deviations between experimental data and calculated values of ST, TPS, DF, and IF modified models are 4.49%, 4.23%, 4.40% and 5.17%, respectively. Therefore, surface wettability reduces the friction between the oil phase and the pipe wall, and the oil film and oil-sticking layer increase the pipe flow resistance.