Abstract:

In this paper, the reservoir microstructures of mudstone and sandstone from Qilian Mountain permafrost were tested by electron microscopy. Under the microscope, the mudstone is composed of tiny and uniform flaky polygonal blocks, so that the hydrate immerses in the mudstone. The sandstone has dispersed pores inside, thus the hydrate exists in the sandstone by pore-type filling. The thermal conductivity and thermal diffusi-vity of reservoirs bearing methane hydrate were measured by transient plane heat source method. At the temperature range of about -9.41 to 9.41 ℃, the thermal conductivities of the dried mudstone and the mudstone bearing methane hydrate are 0.577-0.853 W·m^-1·K^-1 and 0.704-1.050 W·m^-1·K^-1, respectively. At the temperature range of about -8.11 to 9.28 ℃, the dried sandstone and the sandstone bearing methane hydrate have thermal conductivity of 0.828-1.271 W·m^-1·K^-1 and 3.850-4.555 W·m^-1·K^-1, respectively. At the temperature range of about -9.41 to 9.41 ℃, the thermal diffusivities of the dried mudstone, the mudstone bearing methane hydrate, the dried sandstone, and the sandstone bearing methane hydrate are 0.712-0.894 mm²·s^-1, 0.792-1.006 mm²·s^-1,1.198-1.674 mm²·s^-1, and 1.403-1.769 mm²·s^-1,respectively. The data show that it is a good means to explore the existence of hydrate by measuring the thermal conductivity of intervals bearing gas hydrate.

Key words: gas hydrate, thermal conductivity, thermal diffusivity, microstructure, mudstone, sandstone