Research on Prediction of A-Annular Pressure Buildup of Deepwater Gas Wells at the Initial Stage of Production

In the early production stage of deepwater gas wells, the A-annular pressure increases rapidly. It approaches the casing strength limit due to high-temperature fluid, which seriously threatens the integrity and safety of the wellbore. A wellbore temperature distribution prediction model is established for the safe production of deepwater gas wells based on the energy conservation equation and the wellbore heat transfer processes. Considering the effect of temperature and pressure changes on the physical parameters of the annular fluid, the thermal expansion coefficient and isothermal compression coefficient of the annular fluid are fitted as a function of temperature and pressure, and on this basis, the prediction model and analysis method of the annular pressure during the production of deepwater gas wells are established. The A-annular pressure prediction under variable temperature and pressure conditions is realized. The results show that the prediction error of the prediction model considering only the influence of temperature is significantly greater than that of the prediction model considering the influence of temperature and pressure. The new model is suitable for the prediction of A annular pressure with different production rates and different production times. The prediction error of the model is less than 7%, which provides theoretical guidance for the formulation of the annular pressure control scheme on site.