Geomechanical Behavior of Gas Hydrate-Bearing Reservoir during Gas Production

Abstract

Deformation of gas hydrate-bearing reservoir may pose a risk of geohazard. While recent advancement in laboratory experiments has provided insights into geomechanical behavior of gas hydrate-bearing sediments in a phase-stable condition, its behavior under non-uniformly evolving multi-physics conditions, happening during gas production, is more complex and requires rigorous investigation. For example, deformation of gas hydrate-bearing sediments may be enhanced by the change in hydrate-dependent sediment permeability as it alters pore pressure field and also by non-uniform hydrate dissociation as dissociating sediments release their stresses, which need to be carried by the neighboring sediments. Therefore, it is crucial for accurate deformation prediction to adopt a soil model that captures the behavior of gas hydrate-bearing sediments and comprehensively model the complex process during gas production. This study provides the importance of capturing volumetric deformation and hydrate dissociation-induced stress relaxation through simulations of 30-day gas production from homogeneous gas hydrate-bearing reservoir via depressurization. It is found that, for accurate prediction of reservoir deformation, a soil model needs to consider volumetric yielding. In addition, as volumetric deformation affects sediment permeability, gas production is also affected by volumetric deformation. These findings demonstrate that geomechanical modeling plays a key role not only for predicting potential geohzard but also for an estimate of gas production.

AAPG Datapages/Search and Discovery Article #90348 © 2019 AAPG Asia Pacific Region Geosciences Technology Workshop, Gas Hydrates – From Potential Geohazard to Carbon-Efficient Fuel?, Auckland, New Zealand, April 15-17, 2019