Optimization Of Downhole Throttling Process Parameters For Gas Wells With High Water Content

Using throttling technology in gas wells can effectively reduce wellhead pressure and avoid causing safety accidents.A sudden drop in fluid temperature after throttling may cause the formation of natural gas hydrates.Using downhole throttling technology combined with formation energy to insulate the fluid can prevent the formation of hydrates at the wellhead.Downhole throttling technology can also increase the cumulative production of gas wells through pressure control production,and improve the liquid discharge capacity of gas wells.Aiming at the problems of insufficient liquid discharge capacity and hydrate blockage in the production of high water content gas wells,combined with the advantages of downhole throttling technology,a study was conducted on the optimization of downhole throttling process parameters for high water content gas wells.By studying the shortcomings of existing nozzle flow calculation models,an experimental platform for gas-liquid two-phase throttling was established to study the basic characteristics of fluid motion during throttling,as well as the relationship between nozzle diameter,pressure,gas-liquid ratio,and liquid holdup.A prediction model for gasliquid two-phase nozzle flow was established.Based on the principle of energy conservation and van der Waals theory,a prediction model for throttling temperature drop was established.Based on gas-liquid two-phase pipe flow theory and heat transfer theory,a prediction model for wellbore pressure and temperature distribution in gas wells is established to study the changes in wellbore pressure and temperature distribution in downhole throttling gas wells.Study the formation inflow performance of gas wells,and obtain a gas well production prediction model that integrates throttling,wellbore,and formation.The basic characteristics and formation conditions of hydrate were studied,and a prediction model for hydrate formation was established.The liquid carrying characteristics of gas wells are studied and a prediction model for the critical liquid carrying flow rate of gas wells is established.The results show that the 11 kinds of nozzle flow calculation models commonly used in the field have good accuracy at the initial stage of calculation.With the continuous development of gas wells and the change of their own parameters,the prediction results of these models become significantly worse;The liquid holdup decreases with the increase of gas-liquid ratio,and the smaller the orifice diameter,the more obvious the change,which is caused by the gas-liquid slippage phenomenon;Compared with other11 models,the newly established gas-liquid two-phase nozzle flow prediction model has high accuracy and good adaptability,and the calculation error is 5.76% in 8 example wells;The larger the throttling aperture,the greater the pressure drop after throttling,and the smaller the wellhead pressure.Due to the formation energy,the wellhead temperature changes little;The change of the depth of throttling has little effect on the wellbore pressure and temperature gradient,and only affects the temperature and pressure distribution after throttling;The smaller the gas-liquid ratio is,the more obvious the wellbore pressure gradient is and the lower the temperature gradient is;The minimum running depth of the choke in well test in Changqing is 1400 m,and the hole diameter of the gas nozzle is 5mm.Through CFD simulation of gas-liquid two-phase throttling,it is found that there is pressure loss and fluid backflow on the inner wall of the throttling inlet.By studying the downhole throttling gas well technology research,predicting the law of gas well fluid production,wellbore pressure and temperature distribution under different throttling process parameters,combining with hydrate formation and critical liquid carrying flow judgment,can provide theoretical guidance for the optimization of downhole throttling process parameters of high water content gas wells.