Gas production from layered methane hydrate reservoirs

Abstract

Reservoir simulations are used to find the production strategies for methane gas hydrate reservoirs. Most of these simulation models assume homogeneous reservoirs in absence of substantial well data. Many natural gas hydrate reservoirs are heterogeneous. Majority of the heterogeneity comes from the depositional layering at different geological time scales. Examples are Mount Elbert, block 818 in Gulf of Mexico, Walker Ridge 313 Site. The effect of cross-flow or no cross-flow between the layers is still unknown. In the present work, layered gas hydrate reservoir, underlain by a confined aquifer, with cross-flow between the layers is studied. A 3-dimensional, multi-component, multiphase, thermal, compositional simulator developed by Sun and Mohanty (2005) is used. Earlier work showed that for a confined, homogeneous reservoir underlain by an aquifer layer, depressurization method gives the highest recovery. So, in the present work, only depressurization of the reservoir is considered. In layered reservoirs recovery is found to be dependent on the total volume of the hydrate present in the reservoir, depressurization potential of the reservoir and the enthalpy available for dissociation irrespective of the layering. The layering suggests the positions and progress of the dissociation fronts.