EXPERIMENTAL MODELING OF GAS FILTRATION IN FROZEN AND HYDRATE-CONTAINING ROCKS UNDER UNIAXIAL COMPRESSION CONDITIONS
E.M. Chuvilin1, S.I. Grebenkin1,2, M.V. Zhmaev1,2
1Skolkovo Institute of Science and Technology, Center for Petroleum Science and Engineering, Moscow, Russia
2Sadovsky Institute of Geospheres Dynamics of Russian Academy Sciences, Moscow, Russia
Keywords: frozen sediments, hydrate-bearing sediments, experimental modeling, gas filtration, research methodology, phase transitions, relative deformation, elastic wave velocity
Abstract
Studies show that frozen rock strata can accumulate significant amounts of natural gas both in free form and in the form of gas hydrates. Changes in the thermobaric conditions of gas-bearing permafrost can be accompanied by various gas-dynamic processes that lead to active gas emissions from the upper horizons of permafrost. During the activation of these processes, the gas pressure in gas-saturated horizons can be equal to or even exceed the pressure of the overlying rocks, and pressure gradients can reach a significant value that will be sufficient for deformation of ice- and hydrate-containing rocks, the occurrence of gas filtration, its permeation and breakthrough into the overlying rock layers. To simulate such natural conditions, the authors developed an original technology that included the creation of a special core holder for the filtration system and the development of an algorithm for conducting laboratory tests. In the course of methodological experiments, it was found that at a constant gas pressure of approximately 2 MPa in a heated impermeable ice-saturated sandy clay sample, gas filtration can occur in the region of high negative temperatures, below its thawing temperature. Methodological experiments to study the changes in the gas permeability of frozen and thawing rocks under conditions of the formation and dissociation of methane pore hydrates have shown regular changes in gas permeability due to ice (water)-hydrate phase transitions and structural transformation of the soils caused by these phase transitions.
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