Measurement of effective thermal conductivity of hydrate-bearing sediments and evaluation of existing prediction models

As a potential alternative strategic energy source, and for their potential impact on global climate, natural gas hydrates have garnered worldwide attention. This study explored the measurement of effective thermal conductivity of methane hydrate-bearing sediments and evaluated existing models for the prediction of effective thermal conductivity. A thermistor-based method combined with Micro-CT observations was employed in the determination of the effective thermal conductivity of porous matrix materials with various hydrate and water saturation levels and physical characteristics. The effects of sample component characteristics, including the volume content of hydrate and water, phase conversion, and properties of porous materials, on the effective thermal conductivity of hydrate-bearing sediments were systematically evaluated. The effective thermal conductivity positively correlated with hydrate saturation, water content, and the thermal conductivity of porous media. In addition, the effective thermal conductivity slightly increased with hydrate dissociation, indicating an increasing heat transfer capacity during gas production. Existing prediction models were evaluated using our measured results, and a hybrid model combining the parallel and series models was proposed with expanded applicability to the scope of our research. The feasibility of the proposed model was also verified in a comparison with previous research. The results of this study are important for future investigation of the actual thermal properties of hydrate-bearing sediment and the understanding of the heat transfer mechanism during gas production. Furthermore, the results can provide guidance in the selection of an optimal technique for gas production from hydrate deposits at the field scale. (C) 2017 Elsevier Ltd. All rights reserved.