Simulations of Variable Bottomhole Pressure Regimes to Improve Production from the Double-Unit Mount Elbert, Milne Point Unit, North Slope Alaska Hydrate Deposit

Gas production was predicted from a reservoir model based on the Mount Elbert gas hydrate accumulation located on the Alaska North slope at various simulator submodels and production scenarios. Log, core, and fluid measurements were used to provide a comprehensive reservoir description. These data were incorporated with experimentally derived saturations, porosities, permeability values, parameters for capillary pressure, and relative permeability functions. The modeled reservoir exposed to depressurization at a constant bottomhole pressure (2.7 MPa) has shown limited production potential due to its low temperature profile. To improve production the bottomhole pressure was allowed to vary from 2.7 (above the quadruple point) to 2.0 MPa over a 15-year period. The results indicate that gas production was nearly doubled in comparison with a constant-pressure regime. Extensive ice formation and hydrate reformation that could severely hinder gas production were avoided in the variable-pressure regime system. A use of permeability variation coupled with porosity change is shown to be crucial to predict those phenomena at a reservoir scale.