In this work, the self-preservation of small (tens of μm) methane hydrate particles dispersed in oils was studied. The results of this work show that stirring in itself has no effect on the self-preservation of hydrate particles in oil suspensions. The particles undergo self-preservation under both static and stirred conditions. However stirring can lead to redistribution of oil components which may result in the disappearance of self-preservation. Accordingly to developed analytical model, it was shown that the effectiveness of self-preservation is determined by the value of the diffusion coefficient of methane in the pores of the ice crust. It was shown that for the samples with weak self-preservation, the diffusion coefficient of methane in the pores of the ice layer is close to 10−15 m2/s, while for the samples with effective self-preservation this value is an order of magnitude lower. Thus, the pore structure of the ice layer formed on the hydrate particles completely determines whether the self-preservation effect is manifested in a single experiment. The oil environment can allow for the formation of dense ice layers that can provide effective self-preservation. Our data show that the process of the appearance of ice layer and of evolution of its pore system on the surface of hydrate particles suspended in oils and thus the hydrates decomposition rates is of a stochastic nature. Therefore, the efficiency of self-preservation may differ significantly under similar external conditions.
Предметные области OECD FOS+WOS
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