Thermal conductivity of gas hydrate is one of the more important physical properties relevant to drilling, logging, and gas production from natural gas hydrate reserves, however, it is not easy to make direct measurement of thermal conductivity of gas hydrate due to its ephemeral nature at earth surface conditions.
A solid gas hydrate in Section 164-994C-31X-6 was used for measurement of thermal conductivity. The size of the sample was approximately 20 mm x 10 mm x 5 mm. The sample was cut plane to fit the plate probe of a specially designed apparatus to measure thermal conductivity of small samples at elevated pressure. The measurement system is shown in Figure 13. This system has two types of probes for a hot-wire method, a plate probe and a needle probe. We used the plate probe because the sample was hard. The apparatus was cooled to -30ºC, then the sample was inserted and pressurized at 12 MPa for 4 hr before measurement. We measured three times at the same temperature every 4 hr. The data were reported as the average of these three measurements.
Results of the measurement are shown in Table 3 and Figure 14 along with the value reported by Sloan (1990). Thermal conductivity of the Blake Ridge gas hydrate ranges between 0.553 and 0.314 W/(m·K) for temperatures between -30º and 10ºC. The conductivity values decrease with temperature from -30º to 0ºC, then abruptly increase by 0.2 W/(m·K) at 0ºC. This abrupt increase was probably caused by the release of liquid water, the higher thermal conductivity of water increased the thermal conductivity of the system.