A critical production model for deep HT/HP gas wells

Annular pressure buildup always occurs in the production process in deep high temperature high pressure (HT/HP) gas wells. The high annular pressure causes leakage and induces severe accidents, especially in high-sulfur gas reservoirs. Annular pressure increases with the gas production rate. Therefore, it is of great significance to ensure that the production rate is under sustainable rate for deep HT/HP gas wells. However, the critical production rate is not presented in previous research. In this paper, for the security of tubing and production casing, a new critical production model for deep HT/HP gas wells is built, in which the thermal expansion effect and annular volume changing effect are taken into consideration and an iterative method is employed to calculate the annular temperature and pressure distributions by considering the influences of well structure, tubular string combination and fluid composition. Finally, the model is applied to two deep HT/HP gas wells in China. It is indicated that this model provides alternative perspective for production strategy for deep HT/HP gas wells.