Numerical Simulation Study on Regulation Failure of Multiphase Choke Valves in Drilling Well Control

During multiphase flow well control operations, the complex interactions between gas and liquid phases inside choke valves often lead to pressure regulation instability and even control failure, posing a critical challenge to safe and efficient well control. To address the unclear response mechanism of pressure, drop adjustment and the complex phase distribution evolution during multiphase flow through choke valves, a gas–liquid two-phase flow regulation model for drilling well control chokes was established by introducing a slip-velocity correlation to characterize interphase coupling. Numerical simulations were conducted for two representative valve geometries—a needle choke and a wedge choke—under varying gas volume fractions, pressure differentials, and valve openings to obtain the internal pressure drop, velocity field, and phase distribution characteristics. The results indicate that the model achieves an average relative error of approximately 5% and a maximum deviation of 8.7% compared with benchmark CFD results, with pressure prediction accuracy maintained within ±0.2 MPa. When the gas volume fraction exceeds approximately 35% or the pressure differential is in the range of 8–12 MPa under the studied conditions, significant gas–liquid slip and cavitation occur within the valve, causing the flow–pressure relationship to deviate from linearity and reducing regulation sensitivity by about 30%–45%. Moreover, the needle choke exhibits stronger throat contraction effects at small openings, making it more prone to cavitation-induced abrupt pressure drops, whereas the wedge choke shows clearer sensitivity degradation at large openings due to increasing flow channel expansion and aggravated phase maldistribution. These findings elucidate the failure mechanism and critical characteristics of choke regulation under multiphase flow conditions, providing theoretical support for structural optimization of choke systems and rapid pressure stabilization strategies in drilling well control.