Gas Hydrate-Related Pore Pressure Prediction in the Frontier Bay of Bengal

Abstract This study reports pore pressure prediction challenges in gas hydrate-bearing sediments of the offshore Rakhine-Andaman province in the Bay of Bengal. The seismic velocity-based methods fail to correctly differentiate between hydrate effects and true overpressure. The primary objective is to apply and validate an inverse pressure-temperature modeling approach to improve pore pressure estimation and enhance drilling safety in frontier gas hydrate-prone offshore environments. The method incorporates seismic data interpretation to map the base of the gas hydrate stability zone with inverse modeling of hydrate phase equilibrium equations. The main inputs comprise hydrate thickness, seabed temperature, geothermal gradient, and pressure-temperature relations. The estimated pore pressures were compared against conventional seismic velocity-based predictions and supported using actual well observations. The results demonstrate that the gas hydrate stability zone-related empirical phase equilibrium approach delivers better pore pressure estimates with minimal variation, e.g., 0.55 MPa (=80 psi), and good agreement with observed well data. In contrast, the conventional seismic velocity-based method substantially overestimates pore pressure between 1.4–2.8 MPa, likely due to contradictory velocity responses of hydrates and overpressure zones. This can potentially lead to inaccurate mud weight design and enhanced drilling risk. Field data confirms that actual pore pressure is only slightly above hydrostatic i.e., 0.14–0.21 MPa, supporting the validity of this inverse pressure-temperature approach, and thus potentially reducing geohazards and allowing safer well planning in gas hydrate provinces. The technique was compared to published pore pressure observations from the Krishna-Godavari (KG) and Mahanadi Basins, confirming its robustness in diverse geographies.