Gas Production Modeling From a Complex 3-D Description of Marine Gas Hydrate Sand Reservoir

In April and May of 2009, an industry research consortium led by Chevron in collaboration with the U.S. Department of Energy (DOE) National Energy Technology Laboratory (NETL), the U.S. Geological Survey (USGS), the U.S. Minerals Management Service, and others completed a marine hydrate drilling expedition in the Gulf of Mexico. During this 21-day logging-while-drilling (LWD) expedition targeted three drilling sites: Walker Ridge 313, Green Canyon 955, and Alaminos Canyon 21. Seven LWD holes were drilled and gas hydrate-bearing sediments with hydrate saturation greater than 50% were found in at least four wells. Following on this successful Joint Industry Project Leg II expedition, we have constructed a set of reservoir simulation descriptions based on the logging results and pre-drill seismic estimates of the extent and thickness of the gas hydrate deposits at the Walker Ridge 313 and Green Canyon 955 sites.  By constraining the hydrate saturations and thicknesses using the resistivity logs at the drilling sites, reservoir models of complexity varying from two-dimensional homogeneous (cylindrical, r-z) to full three-dimensional, heterogeneous models of the deposits have been simulated. These models have been simulated using the CMG STARS simulator incorporating a non-orthogonal corner point grid to accommodate the geometry of the system. The full, heterogeneous three-dimensional model represents one of the most complete and complex reservoir models of a marine hydrate deposit to date. Results of the reservoir simulations indicate very high potential for producing methane from these marine hydrate deposits using depressurization due to their depth and in situ temperature.