Experimental apparatus for resistivity measurement of gas hydrate-bearing sediment combined with x-ray computed tomography

Abstract

Natural gas hydrate has sparked worldwide interest due to its enormous energy potential. Geophysical surveys are commonly used in gas hydrate exploration, and resistivity logging plays an important role in this field. Nevertheless, the electrical response mechanism as a result of the gas hydrate growth in sediment is not well understood. This study develops an apparatus for the in situ resistivity testing of gas hydrate-bearing sediment combined with x-ray computed tomography scanning. Using this equipment, the gas hydrate samples can be synthesized under high-pressure and low-temperature conditions. The sample resistivities of three different layers can also be measured in situ during the gas hydrate formation. Moreover, x-ray computed tomography scanned gray images are acquired, which can be used to calculate the saturation and analyze the microscopic distribution of gas hydrate. A series of experiments are performed to validate the feasibility of the apparatus. The results show that the sample resistivity shows three distinct stages of variation as the gas hydrate grows. The most sensitive saturation range to the electrical response is ∼10.50%–22.34%. Very few gas hydrate particles will not significantly change the pore connectivity. By contrast, too many gas hydrate particles will hinder the pore network blocking. Both situations will not result in a significant change in resistivity.