Reservoirs Modeling of Gas hydrate deposits in North Slope of Alaska and Gulf of Mexico.

摘要

In order to address the world's growing energy demand, the necessity to explore more and more unconventional sources of energy arises. Recently there has been increased interest in the potential of natural gas hydrates as an alternate energy resource. Methane hydrates are crystalline solids, very similar to ice, in which non-polar molecules are trapped inside the cages formed by water molecules. Methane hydrates could be potentially a vast source of energy. The production of natural gas from hydrates economically poses a big challenge to today's scientific world. Two sites for greatest potential for gas production from gas hydrates as identified by USGS and NETL/DOE are North Slope (ANS) Alaska and the Gulf of Mexico (GOM). In this work specific locations of hydrate deposits are examined, namely the Prudhoe Bay L Pad (PBU L-Pad) and Walker Ridge 313 (WR313) deposits in the ANS and GOM. Reservoir modeling in this work is primarily based on these two gas hydrate deposits.;The uncertainty of reservoir parameters such as hydrate reaction kinetics, the permeability of hydrate bearing sediment, Porosity and permeability of the shale layer boundary on gas production is studied in this work. Gas production from a horizontal well as opposed to a vertical well is evaluated using a mechanistic well bore model. A preliminary assessment of thermal disturbance due to a hot well bore penetrating hydrate deposits in the PBU L pad site is performed using CMG STARS coupled geotechnical model. The results of this study indicate that the extent of hydrate dissociation around a hot wellbore is limited by the thermal diffusion of heat moving radially away from the casing and cement.;In April and May of 2009, the U.S. Department of Energy (DOE) National Energy Technology Laboratory (NETL) in collaboration with the U.S. Geological Survey (USGS), the U.S. Minerals Management Service, an industry research consortium led by Chevron, and others completed a marine hydrate drilling expedition in the Gulf of Mexico called the Joint Industry Project (Leg II) expedition. A complex heterogeneous 3-D model using well log data seismic data are constructed and simulated using CMG STARS and Petrel. An uncertainty assessment of gas production from the WR313 G well on reservoir parameters is performed using a Latin-hyper cube Monte Carlo sampling. Results of the reservoir simulations indicate very high potential for producing methane from these marine hydrate deposits using depressurization due to in situ temperature and pressure related to the great depth of the deposits. The predicted production rates display high (5-40 MMscf/day) rates making the reservoirs to be attractive locations for further exploration. Special cases were considered to estimate influence of permeable over- and under burden on production.