Physical Experiment Research on Dielectric Properties of Hydrate-bearing Sediment in Sandstone Reservoir

Abstract

Dielectric constants can be used to detect hydrates in permafrost regions. Therefore, this study investigated the relationships between the dielectric constant characteristics of sandstone reservoir hydrate and the hydrate saturation degree through physical simulation experiments, as well as the granularity of the surrounding rock. Methane and tetrahydrofuran (THF) hydrates with quartz sands were prepared, and their dielectric constants were analyzed. With different granularities of quartz sands, the dielectric constants of two different methane hydrate sediments decreased with increasing saturation degrees. At a given saturation degree, the dielectric constant of methane hydrate sediments with small granularity was larger than that with medium granularity, a result attributed to the unreacted water in the larger pores of the latter. In addition, the dielectric constant of methane hydrate sediments was larger than that of THF hydrates, which was also attributed to gas-phase factors and the presence of unreacted water. At a given granularity and saturation, the dielectric constants of both the THF and methane hydrates decreased with increasing saturation degrees. We conclude that at low temperature and under normal pressure, THF hydrates cannot be used as a substitute for methane hydrates in laboratory experiments investigating geophysical phenomena.