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Gas production from hydrates dissociation in marine sediments

Abstract:

The quantity of gas accumulated as gas hydrates has been estimated as more than the half of the total fossil energy, and it is considered as the most prominent energy resource to cover the needs of natural gas in the future. Due to the limited data available, important efforts in the harvesting of real data have been carried out and additional simulation studies for this not conventional reservoir like gas hydrates accumulations are considered. The two main mechanisms to define the exploitation strategy are depressurization and thermal stimulation; and reservoir numerical simulation which are considered important tools to get characterization and evaluation of the optimization production process. A three-dimensional commercial numerical simulator is used to model gas production from gas hydrates dissociation, considering the thermodynamic equilibrium and the kinetic intrinsic, both simultaneously. Depending on the defined deposit configuration, gas hydrates accumulations can be associated a biphasic zone with gas free layer below the gas hydrates zone (deposits Class 1), and for this configuration gas production by depressurization is the most favorable one. The initial production from the free gas layer drives the process of dissociation of methane hydrates zone. In the case where the configuration includes the presence of an aquifer or mainly water in a biphasic zone below to the gas hydrates zone (deposits Class 2); the more often evaluated mechanism is hot water or steam injection as thermal stimulation behave like an acceptable alternative for gas production, the rise in temperature promotes the dissociation of the upper hydrates reaching temperatures to that of equilibrium condition. Gas production is associated with water production. Copyright 2010, Society of Petroleum Engineers.