2D and 3D Geomechanical Numerical Simulation for Evaluating Well-Stability and Reservoir Consolidation during the Production from the HYDRATE P1 Well on the Alaska North Slope

Abstract

Methane hydrate production via depressurization can induce geomechanical changes in hydrate-bearing sediments, thereby impacting production performance and risking subsidence and wellbore instability. Here, a fully coupled thermo-hydro-mechanical simulator (COTHMA) is applied to evaluate well stability and to understand reservoir response during an extended methane hydrate production test on the Alaska North Slope. Notably, distributed strain sensing (DSS) measurements from fiber-optic sensors in the wells were used to directly validate the simulation results, providing a unique field-scale assessment of well integrity in relation to reservoir response. Two-dimensional and three-dimensional simulations were conducted for the HYDRATE P1 Production Test Well 1 and HYDRATE P2 Production Test Well 2 (PTW-1 and PTW-2), incorporating in situ reservoir properties, well inclinations, and field depressurization conditions. The simulations successfully reproduce the observed axial strain evolution in the casing–cement system with agreement within the same order of magnitude as the DSS measurements, as well as the associated pore-pressure decline, hydrate dissociation near the wellbore, and stress redistribution in the surrounding formation. Both 2D and 3D analyses consistently indicate that geomechanical responses are strongly localized within a few meters of the production interval and remain spatially limited throughout the production period. The high-resolution 2D analysis suggests that localized plastic deformation may develop in the casing under prolonged depressurization. In addition, the 3D simulations, which explicitly account for well inclination and three-dimensional stress redistribution, indicate that stress anisotropy associated with well inclination has a nonsignificant impact on well integrity under the tested production conditions. The close agreement between simulated and DSS-measured strains confirms the robustness of the coupled framework and supports safe long-term hydrate production with appropriate design.