Transient Surge/Swab Pressure Modeling and Tripping Velocity Optimization in Managed Pressure Drilling with a Choke-Controlled Outlet

Summary Safe drilling in deep and high-temperature/high-pressure (HTHP) wells critically depends on reliable prediction and control of transient surge and swab pressures within narrow safety margins. With this study, we develop a high-fidelity transient pressure model for managed pressure drilling (MPD) that fully incorporates choke settings, HTHP-dependent drilling fluid properties, and drillstring eccentricity. The model employs the interpolated method of characteristics (IMOCs) and is validated by field measurements, with a relative error in peak surge pressure of less than 5%. The model captures key spatiotemporal and frequency-domain characteristics of surge and swab phenomena, including secondary swab effects arising from drillstring tripping-in and the modulation of pressure waves by choke control. Decreasing choke opening increases surge pressure while reducing peak secondary swab pressure. Choke settings modify pressure wave characteristics, with choke-controlled reflections differing from the 180° phase reversal observed in conventional drilling (CD). A systematic parametric study reveals that HTHP conditions reduce surge pressure but intensify the magnitude of the secondary swab effect, emphasizing the risk of underestimating well control challenges if these variations are neglected. Drillstring eccentricity also decreases surge pressure but amplifies the secondary swab effect, especially in deep wells. Global sensitivity analysis (GSA) identifies diameter ratio, drillstring length, and fluid elastic modulus as dominant factors for peak surge pressure and pressure fluctuation amplitude, whereas choke opening primarily affects the peak secondary pressure. A stand-wise tripping speed optimization is performed to minimize operation time while maintaining pressure fluctuations within a safety window. The optimal velocity, acceleration, and deceleration profiles are highly nonlinear and stand-dependent, underscoring the necessity of adaptive, stand-specific control. This integrated approach provides a robust foundation for transient pressure prediction and tripping optimization in MPD, offering practical guidance for safe and efficient field operations in HTHP wells.