CFD and Experimental investigation on Gas-Oil-Water three-phases flow toward the onset of liquid film reversal in a vertical pipe

Liquid loading is a common problem for condensate gas wells as natural gas is always produced with water and condensate. Accurate prediction of liquid loading and proper deliquification measurements are of great significance to stabilize the gas production for gas wells in condensate gas reservoirs. In this paper, Eulerian-Eulerian Multi-Fluid VOF approach was proposed to predict the critical velocity of film reversal. Experimental tests were also conducted to provide data for flow pattern and pressure gradient measurements to validate the numerical simulation model. All tests were conducted based on the visual pipe with a height of 5 m and an inner diameter of 50 mm. The experimental results show that the oil-water-gas flow pattern and pressure gradient agree well with the simulation results. CFD has been carried out to simulate critical velocity of film reversal under the annular flow condition in a 2D vertical geometric model of 62mm in diameter with different water and oil superficial velocities. The velocity profiles show that the slip between the water phase and oil phase can be neglected near the walls, but there is a significant slip phenomenon between gas phase and oil phase in this region. The simulation results show that the value of surface tension and drag coefficient affect the accuracy of the critical velocity of film reversal. For this reason, the Schiller and Naumann drag force model was applied in the simulation method to describe the drag law among condensate oil-water-gas three phases respectively. Compared with the public data of critical velocity in the literature, the absolutely error of simulations was below 15% without considering emulsification of oil-water.