Characterization of Formation Deformation during Production Test from Gas Hydrate in Alaska: A Distributed Fiber Optic Sensing Approach

Abstract Reliable monitoring of geomechanical responses is essential for the safe and sustainable production of gas hydrate reservoirs. This study reports the first field-scale application of distributed strain sensing (DSS) during a 10 month extended gas production test on Alaska’s North Slope. DSS cables installed in production and monitoring wells continuously captured axial and bending strain at high spatial resolution, directly linking depressurization to formation deformation. The observations revealed compressive strain within the hydrate-bearing interval and tensile strain in the surrounding layers, consistent with stress redistribution previously predicted by geomechanical simulations. After the transition from electric submersible pump (ESP) to jet-pump operation, localized bending strain became evident, suggesting possible casing–cement deformation. Interwell measurements further demonstrated strain propagation and physically consistent attenuation away from the production well. Integrated analysis indicated that inward casing–cement deflection during depressurization could have a greater contribution to the measured strain than reservoir compaction and that plastic strain may have developed in the cement where the DSS cable was embedded. This finding emphasizes the need for integrated validation with numerical simulations and additional testing to improve the current quantitative assessment of reservoir deformation, which remains subject to uncertainty. Overall, this study provides the first long-term, field-scale evidence of stress redistribution in hydrate-bearing sediments, establishing DSS as a promising monitoring technology and offering critical insights for reservoir simulation, geomechanical risk assessment, and the future commercial deployment of methane hydrate production systems.