A modified comprehensive prediction model for wellbore temperature-pressure field and liquid loading of gas wells

Abstract

Wellbore liquid loading is a severe problem in the late stage of natural gas production, and precise prediction of liquid loading is helpful for taking dewatering measures timely to avoid the related hazards. Based on the flow and heat transfer mechanisms of gas-liquid two-phase annular flow in wellbore, a new model for calculating temperature and pressure field of the gas well considering the effects of the velocity difference between the gas core and liquid film and the migration of liquid droplets was established first, which laid a foundation for the prediction of liquid loading in the whole wellbore. Then, based on the flow mechanism of liquid film, a liquid loading prediction model for the whole wellbore of gas well was established, with the zero shear force between tubing wall and liquid film under low liquid holdup and the critical liquid holdup of liquid film bridging and plugging gas core taken as criteria for judging liquid loading, and the coupling solution method for the above model was worked out. Production data pairs of gas wells were used to verify the reliability of the model. The results show that our model can accurately calculate the wellbore temperature and pressure of liquid-producing gas wells. The temperatures predicted by the model have a maximum relative error of 11. 86% and an average relative error of 5. 96%, while the pressures predicted have a relative error range from 0. 09% to 8. 42%. In terms of prediction accuracy and prediction error of gas well liquid loading state, the modified model has much more precise prediction results of liquid loading than three classical liquid loading models. Finally, the sensitivity analysis of liquid loading was carried out with an example. The research results can provide theoretical support for the early prediction of liquid loading and dewatering process in liquid-producing gas wells.