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Consolidation of sand formation using Freon-11 gas hydrate Cheng, Wai Keung

Abstract

In this study, the conditions under which gas hydrates form in a porous sand formation were explored. It was established that the permeability of the sand may be greatly reduced by the gas hydrate crystals formed in the pores. Freon-11 gas hydrate was formed in a two-inch sand bed in a high pressure vessel of one-inch diameter under isothermal condition.. Hydrate was found to have been formed in the pores of sand beds of four ranges of particle sizes from 24 mesh to 60 mesh. Laboratory tests showed that the hydrate thus formed could sustain a hydraulic pressure of 1000 psia across the two-inch bed. A subcooling of about 5°C was required for the hydrate to form in sand pores and eliminate its permeability. The hydrate melted at its critical temperature which was higher than its nucleation temperature. The time required for the hydrate crystal to grow to a size large enough to block the pores of the bed was about two hours. In practice, this would allow sufficient time for the hydrate forming agent to be forced to a large area from one injection point. The amount of hydrate forming agent required to block the sand pores was found to be approximately that calculated from the ideal composition of the hydrate. The result of this study shows that the hydrate formation process in pores of a sand bed behaved as predicted by the thermodynamic properties of the hydrate. Thus, although only Freon-11 gas hydrate was used in this study, any other hydrate former or mixture of hydrate formers may be selected for this use if their thermodynamic properties match the conditions in the porous formation.

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