Abstract

Since huge amounts of methane are bounded in natural gas hydrates occurring at all active and passive continental margins and in permafrost regions, the production of natural gas from hydrate bearing sediments becomes more and more of interest. Three different methods for the release of methane gas from destabilized hydrate 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 methane. The heat of the flameless, catalytic oxidation of methane was used for the decomposition of hydrates in sand in a pilot plant scale within a large reservoir simulator (LARS). 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 methane hydrate are presented in this study. The data analysis showed that 15 % of the methane gas released from hydrates would have to be used for the successful dissociation of all hydrates in the sediment using catalytic combustion of methane.

Highlights

  • Clathrate hydrates are ice-like solids composed of a three-dimensional network of hydrogen-bonded water molecules that confines gas molecules in well-defined cavities of different sizes

  • The striking advantage of using thermal stimulation via in situ combustion for the gas production from natural gas hydrates is the position of the heat source: the reactor is located within the hydrate-bearing sediments, the heat is generated where it is needed without any losses of energy during transportation

  • The production test was performed in the LArge Reservoir Simulator (LARS), which has been described in detail elsewhere [2]

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Summary

Introduction

Clathrate hydrates are ice-like solids composed of a three-dimensional network of hydrogen-bonded water molecules that confines gas molecules in well-defined cavities of different sizes. We will focus on the thermal stimulation method, which was already tested successfully in a field test in the framework of the Mallik Scientific Drilling Project in the Northwest Territories in the Canadian Arctic during the winter of 2001/2002 During this gas production test a hot fluid was pumped through about 600 m of permafrost into depths of 900–1100 m where the hydrate-bearing sediment occurred. An alternative method to thermal stimulation via hot fluid circulation may be in situ combustion of CH4 in a counter-current heat-exchange reactor. The striking advantage of using thermal stimulation via in situ combustion for the gas production from natural gas hydrates is the position of the heat source: the reactor is located within the hydrate-bearing sediments, the heat is generated where it is needed without any losses of energy during transportation. Recent results from production tests in a pilot plant scale are presented and discussed

Catalyst Test
Heating and Production Test
The Counter-Current Heat-Exchange Reactor
The Catalysts
The Gas Supply
Conclusions

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