Study Advancement for Multiphase Flow and Heat and Mass Transfer Characteristics for Gas Hydrate Decomposition in South China Sea Offshore Sediment

Gas hydrates are crystalline solids that consist of gas molecules, usually methane, surrounded by water molecules. According to the phase equilibrium characteristics of gas hydrate, there are three basic development methods, including heating, pressure decreasing and chemical injecting. The development process is actually the multi-phase flow process. Currently, there is no good commercial software used to simulate the multiphase flow, heat transmission and mass transfer in the gas hydrate decomposition process. The study is not mature, still in the development and trial stage. So in this paper, we will make a deeply study on the multi-phase flow simulation method of gas hydrate decomposition in the sediment. We try to make breakthrough in the theory and simulate method. According to the different scales, the simulation computation study of flow characteristics model has microcosmic, mesocosmic and macrocosmic scales. In this paper, mesocosmic scales is used to study for the multiphase flow, heat and mass transfer in the offshore gas hydrate decomposition process, and numerical simulation and experimental simulation are together used to study. Study advancements are shown as follows: firstly, conventional Lattice Boltzmann model is modified to new Lattice Boltzmann Model (LBM) based on sediment with gas hydrate and flow characteristics for gas hydrate decomposition, the interaction and density difference between the phases are considered, and Magnetic Resonance Imaging (MRI) visual technology is used to successfully verified to LBM methods. Secondly, contraction core reaction methods based on fractal theory is used to simulate heat and mass transfer in the offshore gas hydrate decomposition process and is successfully verified by experimental simulation for South China Sea offshore gas hydrate sediment.