Hydrodynamic Model For Intermittent Gas Lifting of Viscous Oil

Abstract

Abstract A hydrodynamic model was developed for intermittent gas lift. Simulation results were verified by experimental tests conducted with a 60 ft high 3 in. diameter test facility using air and an oil with viscosity of 108 cp. The simulation program was also successfully applied to data gathered on an instrumented intermittent gas lift well. Results of the study indicate that initially the liquid slug undergoes a rapid acceleration and then accelerates at a much lower rate until the surface is reached, at which time rapid slug acceleration again occurs. It was found in this study that a significant portion of the liquid produced at the surface sometimes more than 50 percent, was contributed during the afterflow (i.e. liquid recovered in the form of entrained liquid in the gas core). In addition, the study has shown that by increasing the injection pressure, a higher recovery can be achieved more rapidly, but only at the pressure, a higher recovery can be achieved more rapidly, but only at the expense of increased gas injection. The model is also capable of predicting the cuing to tubing pressure ratio at which a minimum GOR will predicting the cuing to tubing pressure ratio at which a minimum GOR will occur. This minimum GOR pressure ratio was found to be sensitive to fluid viscosity.