Numerical simulation and field application of supersonic atomization and drainage gas recovery technology: A case study on the middle-shallow gas reservoirs in the Western Sichuan Depression

In view that the application of supersonic atomization and drainage gas recovery technology in the middle-shallow gas reservoirs of the Western Sichuan Depression is lack of theoretical guidance, this paper carried out numerical simulation researches and field tests. Firstly, the numerical model of supersonic atomization nozzle was established based on the actual working conditions of production wells in the middle-shallow water bearing gas reservoirs of Western Sichuan Depression, and two-phase flow in the nozzle was numerically simulated focusing on the production performance of gas wells. Then, the correctness of the model was verified by means of laboratory experiment, and the distribution of the flow characteristic parameters of each phase of the fluid inside the atomization nozzle was solved. Finally, sensitivity analysis was carried out on gas well’s production characteristic parameters and nozzle’s structural parameters, and the main factors influencing the application effect of supersonic atomization and drainage gas recovery technology were determined. In addition, theories of supersonic atomization and drainage gas recovery technology suitable for the middle-shallow gas reservoirs of the Western Sichuan Depression were formed. It is indicated that nozzle’s convergent section has less influence on the flow behavior of fluid, while characteristic parameters of fluid change greatly when it flows through nozzle’s throat and divergent section. When the gas is accelerated to the acoustic velocity while flowing through the atomization nozzle, the critical pressure ratio is 1.35, which can be taken as the technological indicator to judge the technological effectiveness. The inlet pressure has greater influence on the overall technological effect, while the influences of gas production rate and gas/liquid ratio on the technological effect are mainly reflected through controlling the liquid carrying in the hole section before the nozzle inlet and the liquid loading which is carried into the nozzle by the gas is atomized under the action of supersonic gas flow. Based on theoretical researches, the construction parameters were designed and gas wells were selected to perform field tests. It is revealed that supersonic atomization and drainage gas recovery technology can achieve throttling and pressure stabilization of gas wells while enhancing the liquid carrying capacity of water producing gas wells, improving the flow regime in the well and reducing the pressure loss in the well. The research results are of great significance to prolong the stable production period of middle-shallow gas wells in the Western Sichuan Depression.