A Counter-Current Heat-Exchange Reactor for the Thermal Stimulation of Hydrate-Bearing Sediments

Abstract

Since huge amounts of CH₄ are bound in natural gas hydrates occurring at active and passive continental margins and in permafrost regions, the production of natural gas from hydrate-bearing sediments has become of more and more interest. Three different methods to destabilize hydrates and release the CH₄ gas are discussed in principle: thermal stimulation, depressurization and chemical stimulation. This study focusses on the thermal stimulation using a counter-current heat-exchange reactor for the in situ combustion of CH₄. The principle of in situ combustion as a method for thermal stimulation of hydrate bearing sediments has been introduced and discussed earlier [1,2]. In this study we present the first results of several tests performed in a pilot plant scale using a counter-current heat-exchange reactor. The heat of the flameless, catalytic oxidation of CH₄ was used for the decomposition of hydrates in sand within a LArge Reservoir Simulator (LARS). Different catalysts were tested, varying from diverse elements of the platinum group to a universal metal catalyst. The results show differences regarding the conversion rate of CH₄ to CO₂. The promising results of the latest reactor test, for which LARS was filled with sand and ca. 80% of the pore space was saturated with CH₄ hydrate, are also presented in this study. The data analysis showed that about 15% of the CH₄ gas released from hydrates would have to be used for the successful dissociation of all hydrates in the sediment using thermal stimulation via in situ combustion.