Dynamic analysis for two-phase vortex flow and optimization of vortex tools to unload liquid from gas wells

Abstract

Vortex drainage gas recovery is a new technology to unload liquid from gas wells. However, its operating mechanism and efficiency are still not clearly understood, the dynamic analysis model in the wellbore two-phase vortex flow is still lacking. In this study, the forces of the liquid film in the wellbore gas-liquid vortex flow are analyzed based on the two-phase fluid dynamic theory. A dynamic analysis film model for prediction of the pressure drop in the wellbore two-phase vortex flow and the optimal helical angle of vortex tools is established. Besides, the physical simulation experimental facilities were set up and the wellbore two-phase vortex flow was obtained. Various parameters with vortex tools, including the wellbore pressure drop, the operating envelope and the critical flow rate, were examined. The influences of structure parameters of vortex tools on the drainage effect were analyzed. These structure parameters include the flow section of the flow channel, the leak-tightness around the flow channel and the helical angle. The vortex tool which has the best drainage effect was chosen and tested, and the extent of reduction of the critical flow rate with the optimal vortex tool was determined. Then, a liquid loading gas well in the field was chosen. Vortex tools were optimized and used in the wellbore of the gas well. The dynamic analysis model is verified by the experiment and field test. The results show that the dynamic analysis model of the liquid film in the wellbore two-phase vortex flow is reasonable. The effectiveness of vortex tools can be improved by enhancing the leak-tightness on both sides of the flow channel and reducing the flow section of the flow channel. After installing the optimal vortex tool, the wellbore pressure drop decreased by about 9.6%, the liquid flow rate increased by about 12.4% and the critical flow rate decreased by about 20%. The helical angle of the vortex tool has an optimal value, which can be calculated by using the dynamic analysis model. Research results may provide theoretical guidance for the optimization and design of vortex tools.