Numerical solutions of heat transfer problems in gas production from seabed gas hydrates

Abstract

The natural gas in gas hydrates is considered as a major resource of future clean energy. Producing natural gas from gas hydrates at seafloor presents a great challenge to the engineers due to low efficiency in heat transfer processes. A numerical model was developed in this study to investigate the temperature profiles along the hose assembly in the MRM for harvesting the natural gas from hydrates at the seafloor. Sensitivity analyses were carried out to find major factors affecting the delivering water temperature to the gas hydrate deposits. The result shows that decreasing the temperature of the injected water at surface will cause drop in the delivery temperature of water in the pipe. The drop in the surface temperature is transferred almost by the same amount to the drop in the delivering temperature with the pipe insulation used. The temperature of the water delivered to the gas hydrates drops slowly and linearly with water depth at high water injection rate, and sharply and non-linearly with water depth at low water injection rate. The delivery water temperature is strongly controlled by the pipe insulation but insensitive to it when the thermal conductivity of the insulation material is less than 0.0245 W/m-oC. The temperature in the riser annulus is not essentially affected by any of the invested parameters. A comparison between the numerical model and analytical model under the condition of homogeneous mixture flow was performed. The result shows a good agreement between them, which verified the numerical model.