A comprehensive prediction model of wellbore temperature, pressure and accumulated liquid for gas wells

Accumulated fluid in gas well is a key issue confronted in development design of water-producing gas pools and production management of gas wells, but at present, there are controversies on flow mechanism and water carrying prediction in gas wells. From the basic flow mechanism of two-phase flow of gas and liquid, a comprehensive prediction model was built to predict the flow pattern, temperature, pressure and water-carrying in gas wells, and this model was verified using actual well data. The result shows that the model so built can be used to predict the wellbore temperature and pressure of water-producing vertical wells, deviated wells and horizontal wells, and the prediction error is less than 5%. Under condition of annular mist flow, the fluid in the wellbore is carried out of the wellhead completely in the forms of liquid drop and membrane, so no wellbore water shall be accumulated; for conventional vertical gas wells, the wellhead data can be used to determine the accumulated fluid in gas wells; the critical value of liquid carrying in gas wells calculated by Turner model is larger than the actual value, and that calculated by Li Min model is on the small side. So it is suggested that Peng Chaoyang Model be used to calculate the liquid-carrying critical value in gas wells. For deviated wells and horizontal wells, the effects of drop deformation and hole deviation should both be considered. The liquid-carrying critical flow velocity and flowrate in horizontal section in horizontal wells is obviously smaller than that in vertical wells, while the liquid-carrying critical flow velocity and flowrate in angle buildup section first increases with the hole drift angle, but then decreases, reaching the peak when hole drift angle is between 30°and 60°, so angle buildup section is a key place for determination of accumulated fluid in gas wells.