Thermo-pressure coupling modeling of gas invasion in ultra-deep drilling operations

Abstract Accurate modeling of downhole pressure variations in ultra-deep wells constitutes a critical component in post-kick well control strategies. To address this problem, a two-phase flow model is constructed using the drift-flux theory, a heat transfer model was developed based on the law of conservation of energy, and the thermo-pressure field coupling is implemented by incorporating the calculation method for the properties of HTHP fluids. Through the sensitivity analysis of gas kick depth, flow rate, formation permeability, casing pressure, and bottomhole pressure differential, the following key conclusions are as follows: the riser pressure drop increases when gas kick occurs in shallower formations, formation permeability increases, bottomhole pressure differential decreases, or casing pressure rises. The standpipe pressure increases with higher pressure. This research provides valuable insights for pressure control during gas kicks in ultra-deep wellbores.