Two-phase flow chokeling results and control in high-pressure gas wells producing water

Prediction and control of two-phase flow chokeling in tight gas wellbores are essential for the normal operation and hydrate control of high-pressure gas wells producing water. The thermodynamic differential equations of energy, kinetic energy and temperature and models of chokeling field for two-phase energy, system heat, mass balance and flow were developed under the conditions of isentropic adiabatic, isobaric heat capacity, constant volume heat capacity, and chokeling energy. A methodology on predicting characteristics and control of two-phase flow before and after chokeling was proposed for gas-water two phase flow. It provided a theoretical basis for optimizing the structural parameters of downhole throttle and its nozzle and ensuring the flow safety. The dynamic variations of two-phase flow chokeling with nozzle size and its depth, water content, pressure and temperature were analyzed on numerical simulation and verification of Daning-Jixian oilfield in the eastern margin of Ordos Basin. The results show that the mass flow rate increases exponentially with the decreased pressure ratio, and it reaches the maximum while pressure ratio drops to the threshold of 0.55. The temperature will be enhanced after chokeling and the formation of hydrates will be inhibited while the nozzle depth and water content are increased and pressure and temperature are reduced before chokeling. The effects of nozzle inner diameter, water content, pressure, temperature and nozzle depth on the critical mass flow gradually decreases during chokeling. The increase of water content will enhance the critical mass flow rate and decrease gas production of high-pressure gas wells producing water. The well site analysis on Daning-Jixian oilfield shows that the mass flow rates increase 179.3% and 27.8%, respectively, while nozzle inner diameters enhance from 3.0 mm to 5.0 mm and pressures on chokeling process increase from 14 MPa to 18 MPa. The mass flow rate varies with a small drop of 5.15%. Increasing the nozzle inner diameter, its depth and the pressure while reducing the temperature is beneficial to improve the mass flow rate during the chokeling process of two-phase fluid and increase the gas production in high-pressure gas wellbores producing water.