Comparisons of different simulated hydrate designs for Class-1 gas hydrate deposits

Hydrates can be modeled as an extremely-high-viscosity oil-phase component or a solid-phase component. The fact of the support from a solid hydrate on the formation strength can be proved by comparing different hydrate phase design models. The purpose of this study is to compare the production behaviors and geomechanics effects between the oil-phase and the solid-phase hydrate models in order to investigate the support of solid hydrates on the formation deformation and seabed subsidence. In this study, a modification method is proposed to modify the parameters of initial flowing-phase saturations and the corresponding relative permeability curves used in the solid-phase hydrate model to avoid a problem of overestimated water production and to achieve the calculation agreement between two different hydrate design models. The effects of different hydrate phase designs on the production profiles and the formation deformation of a Class-1 hydrate deposit is studied in the cases with coupling the geomechanics module. We found that the cumulative gas production is slightly higher in the coupled solid-phase hydrate model than that in the coupled oil-phase hydrate model. The observations of the seabed subsidence from the two coupled hydrate models show that the quantity of seabed subsidence of the coupled solid-phase hydrate model is lower than that of the coupled oil-phase hydrate model, which leads to the proven of the fact of the support of solid hydrates on the formation strength.