Study on Optimization of Methane Hydrate Production System by Using Genetic Algorithm

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There is no method established for recovering gas economically from subsurface hydrates because they exist as the solid sate, which is different from conventional oil and gas. In this study, we carried out laboratory experiments to clarify dissociation behavior of hydrates in sediments, and numerically evaluated hydrate production system. For finding appropriate gas production systems, we applied an optimization method using genetic algorithm.(1)Experiments on formation and dissociation of hydratesAn experimental apparatus was built for observing formation and dissociation behavior of hydrates in sediments. Experiments were carried out to analyze pressure/temperature behavior during formation and dissociation of CO2 hydrate in Berea sandstone core. The analysis of experimental data showed that gas recovery rate from hydrates in depressurization was much influenced by heat transfer from the surroundings, initial hydrate saturation, and permeability of sediments.(2)Economic evaluation fo … More r a hypothetical hydrate sedimentSimulation studies were carried out to investigate feasibility of hydrate gas production. The results showed that the following parameters were important to determine gas productivity from hydrates : well configuration (vertical and horizontal settings of well) ; length of horizontal section ; and thermal conductivity of upper and lower sediments adjacent to the hydrate sediment.(3)Production system optimization using genetic algorithmOptimization studies were carried out for a gas recovery process injecting hot water into hydrates in offshore Japan. Production parameters as temperature of injected water, volume of water injected, production period, and length of well horizontal section were optimized by using net present value of the gas recovery project as an objective function. This study showed a guideline for optimization of hydrate production system, although the calculated results were not precise due to a simplified geological model assumption because of little field data available on hydrate occurrence and amounts. Less