Velocity and Resistivity Measurements of Artificial Gas-hydrate-bearing sediment.

An experimental device designed and developed to grow methane hydrate in the pore space of a sediment was successfully used with a glass bead sample. The underlying idea for the experiment is that methane dissolved in water is transported with upward moving fluids from its place of origin at greater depths to formations in the hydrate stability field where the methane is removed from the pore water to form hydrate. This process is simulated in a closed loop flow system in which methane charged water from a gas/water reservoir outside the hydrate stability field is pumped into the sediment sample cell in the stability field for methane hydrate. The fluid depleted of methane, then flows back into the gas/water reservoir to be recharged with methane.
The electrical resistivity and sonic wave velocity was measured during the process of hydrate formation from methane dissolved in the pore water without a free gas phase. In addition to the sample properties, we measured the resistivity of the circulating water in order to determine the amount of water consumed by hydrate formation from the increase of salinity and to determine the formation resistivity
factor and resistivity index. The electrical resistivity and sonic velocity of the sample increased from 5.1 Ωm and 2036 m/s at 100% water
saturation to 265 Ωm and 3770 m/s at about 95% hydrate saturation, whereas the water resistivity decreased from 1.39 to 1.08 Ωm.