A new effective thermal conductivity model of methane hydrate-bearing sediments considering hydrate distribution patterns

Abstract

In this work, a new effective thermal conductivity (ETC) model considering hydrate distribution patterns was proposed to study the effects of hydrate saturation (nh), distribution pattern and pore fluid. The ETC of methane hydrate (MH)-bearing sediments with liquid- saturated state (only water and MH in pores, i.e., “liquid-saturated” sediments), gas saturated state (only methane and MH, i.e., “gas-saturated” sediments) or hydrate-saturated state (only MH in pores, i.e., nh = 100%, “hydrate-saturated” sediments) were calculated by the proposed ETC models with the temperature 263.15∼278.15 K, the pressure 6 MPa and the porosity 47.64%. The calculated results show that the ETC of hydrate-saturated sediments is about 1.44±0.04 W·m−1·K−1; the ETC of liquid-saturated sediments ranges from 1.42 to 2.2 W·m−1·K−1, showing a weak negative correlation with nh, and a positive correlation with temperature. However, the ETC of gas-saturated sediments ranges from 0.15 to 1.45 W·m−1·K−1, which is positively correlated with nh, negatively (or positively) correlated with temperature at low nh (or high nh). Besides, the results suggest that the ETC increment caused by the temperature increase of 1 K is -3.6E-4∼2.34E-3 W·m−1·K−1 under the three hydrate distribution patterns and three above states, which can be seen as a weak dependence on temperature. The influence of distribution patterns on the ETC of gas-saturated sediments (with the same nh) is: cementing model > inclusion model > filling model. Due to the particularity of the structure of the supporting model, the ETC of sediments is mainly affected by sand content (vs), but weakly affected by hydrate content (vh) and hydrate growth mode. Increasing the same value of vs and vh, the ETC increment of the former is about 10 times that of the latter. Finally, the new ETC models are used to predict hydrate content of natural sea sand and marine soil samples, which provides a new idea for resource evaluation.