Predictive analysis on borehole temperature and pressure of HTHP gas wells considering coupling effect

Temperature and pressure are two important parameters for daily production management and dynamic design and analysis of gas wells. a coupled prediction model of temperature and pressure distribution was developed according to the laws of conservation of momentum and energy and the basic principles of mass transfer and heat transfer. In this model, the factors influencing temperature and pressure are taken into account comprehensively. The model is divided into two parts, i.e., pressure model and temperature model. In the pressure model, the effects of fluid gravity, friction resistance and dynamic variation inside the borehole are considered. In the temperature model, the heat transfer inside the borehole is treated as steady-state heat transfer while that in the strata is treated as unsteady-state heat transfer, and the effect of borehole heat loss on temperature is considered. Then, the model was coupling iteratively solved by means of fourth order Runge-Kutta method. Finally, the model was verified and analyzed by using the measured data of Well X in one certain gas field in Sichuan. Sensitivity analysis was conducted on borehole temperature and pressure with the bottom hole as the reference at different production rates, relative gas density and production time. And the prediction result of coupling model was compared with that of linear model. It is indicated that with the increase of production rate, borehole pressure drops and borehole temperature rises. With the increase of gas density, borehole pressure drops and borehole temperature rises. With the increase of production time, borehole pressure basically remains constant and borehole temperature rises. And borehole temperature changes nonlinearly with the well depth. The research results can be used as the guidance for the selection of pipe strings with suitable properties and the safe operation of pipe strings.