Flow and Heat Transfer Analysis of Natural Gas Hydrate in Metal-Reinforced Composite Insulated Vertical Pipes

The extraction of land gas resources requires efficient methods to address the issue of pipeline obstruction due to the accumulation of natural gas hydrates. The existing ground heating, downhole throttling, and decompression measures are energy-intensive. The metal-reinforced composite heat-insulation pipe serves as the production string for terrestrial natural gas wells, effectively minimizing temperature loss of natural gas within the wellbore. This innovation eliminates the need for ground heating equipment and downhole throttling devices in large-scale gas well production, thereby fundamentally achieving environmentally sustainable natural gas extraction, energy conservation, and cost reduction. This research simulates the operational circumstances and environmental characteristics of the Sulige gas field. Utilizing predictions and analyses of the formation characteristics of natural gas hydrate, the gas–solid two-phase flow DPM model, RNG k-ε turbulence model, heat transfer characteristics, and population balance model are employed to examine the concentration distribution, pressure distribution, velocity distribution, and heat transfer characteristics of natural gas hydrate within the vertical tube of the structure. The findings indicate that a reduction in natural gas production or an increase in hydrate volume fraction leads to significant accumulation of hydrate adjacent to the tube wall, while the concentration distribution of hydrate is more uniform at elevated production conditions. The pressure distribution of hydrate under each operational state exhibits a pattern characterized by a high central concentration that progressively diminishes towards the periphery. The unit pressure drop of hydrate markedly escalates with an increase in flow rate. As the ambient temperature of the formation rises or the flow rate escalates, the thermal loss of the hydrate along the pipeline diminishes, resulting in an elevated exit temperature. Minimizing the thermal conductivity of the composite pipe can significantly decrease the temperature loss of the hydrate along the pipeline, greatly aiding in hydrate inhibition during the extraction of natural gas from terrestrial wells. This paper’s research offers theoretical backing for the enduring technical application of metal-reinforced composite insulating pipes in terrestrial gas fields, including the Sulige gas field.