Massively Parallel Simulation of Production from Oceanic Gas Hydrate Deposits

The quantity of hydrocarbon gases trapped in natural hydrate accumulations is enormous, leading to significant interest in the evaluation of their potential as an energy source. It is known that large volumes of gas can be readily produced at high rates for long times from some types of methane hydrate accumulations by means of depressurization-induced dissociation with conventional horizontal or vertical well configurations. However, most assessments of hydrate production use simplified or reduced-scale 3D or 2D production simulations. In this study, we use the MPI-parallel TOUGH+HYDRATE code (pT+H) to make the first field-scale assessment of a large, deep-ocean hydrate reservoir. Systems of up to 2.5M gridblocks, running on thousands of supercomputing nodes, are required to simulate such large systems at the highest level of detail. The simulations begin to reveal the challenges inherent in producing from deep, relatively cold systems with extensive water-bearing channels and connectivity to large aquifers, mainly the difficulty of achieving depressurization and the problem of water production. Also highlighted are new frontiers in large-scale reservoir simulation of coupled flow, transport, thermodynamics, and phase behavior, including the construction of large meshes, the computational scaling of larger systems, and the complexity and resource-intensiveness of large-scale volume visualization of unstructured meshes.