Experimental Characterization of Production Behaviour Accompanying the Hydrate Reformation in Methane-Hydrate-Bearing Sediments

Abstract

Summary This paper experimentally analyzes the production characteristics of hot-brine stimulation accompanying hydrate reformation in the presence of methane hydrate. Many attempts have been made to recover methane hydrate commercially, such as depressurization, thermal stimulation, and inhibitor injection. Hot-brine injection coupled with thermal recovery with inhibitor injection has been investigated as an efficient production scheme, but the hydrate reformation during the dissociation is problematic, and it negatively influences the recovery rate. An experimental apparatus divided the sediment sample into 12 blocks not only to describe 1D dissociation effectively but also to control the temperature accurately. The specified amount of methane hydrate was formed artificially in unconsolidated and packed sediments where the average particle size, absolute permeability, and porosity were 260 µm, 4.4 darcies, and 42%, respectively. The production trends were observed in the temperature range of approximately 283.85 - 303.15 K and with injection rates of 10 and 15 cm3/min. Methane hydrate reformed in all the tests; the reason for this may be the recombination of water and the dissociated methane in the downstream zones. In the early time, the production rate was low, but it increased significantly in later time. The former was why most of gas that dissociated in the upstream zones was consumed to reform hydrate in the downstream areas, while the latter came from the dissociation of initial and reformed hydrate. The dissociation front moved fast at the higher temperature and injection rate. The production efficiency of the test at 15 cm3/min and 294.55 K was similar to that of the test at 10 cm3/min and 303.15 K. The results confirmed the production behaviour of methane hydrate under the reformation phenomenon and could provide the fundamentals to develop an efficient production scheme based on hot-brine stimulation.