Fundamental Study On Gas Hydrate Formation Characteristics

In the recent years, shortage of energy,environmental degradation are the main problems of the world. So searching efficient and clean energy is the urgent task of our human. Because of the advantages of aboundance resource,wide distribution,high energy density and clean combustion, methane hydrate is expected to be the most potential energy for exploitation in the 21th century. Carrying out studies on basic properties of methane hydrate and production methods of methane hydrate has great theoretical and practical significance. This study focuses on formation kinetics of methane hydrate which needs further research and study. The experimental platform to simulate hydrate formation in porous media is designed and built. The study simulates porous meida by using uniform glass beads to study formation and reformation of the structure I and II hydrate. Experiments focus on the study of effected factors and variation of induction time and saturation during hydrate formation process, which can give support on the study of formation kinetics with experimental data and theory.The results indicate that both structure I hydrate (mehane hydate and carbon dioxide hydrate) and structure II hydrate (propane hydrate) have evident induction time during the formation process. In addition, the induction time decrease along with the decrease of diameter of glass beads, which is also proved by using magnatic resonance imaging systerm (MRI) that the induction time is effected with the change of pressure,temperature and size of porous media. The methods of acquiring and contrling saturation of hydate in prous media are also studied which have a conclusion that the saturation can be controlled by changing volume of gas and primary pressure. The study also showed that the saturation of hydrate in porous media grow along with the increase of size of porous media.The study also carried out experiments on hydrate reformation in porous media based on the hydrate formation experiments. The experiments on hydrate formation and reformation (or more times) with same object gas indicated that structure I hydrate (mehane hydate and carbon dioxide hydrate) formation and reformation have an evident memory effect by using theirself dissociation water. The induction time of methane hydrate decrease with the decrease of size of glass beads when the size of porous media (BZ01,BZ02) is much small, while in the large size of porous media (BZ04,BZ06), no obvious induction time was observed during the process of hydrate reformation. The reformation time grow along with the decrease of size of glass beads when the hydrate reformation in the Z01,BZ02,BZ04 and BZ06 glass beads. The experiments on hydrate formation and reformationwith different object gas indicated that not only the memory effect was obvious in the structureâ… hydrate during the process of formation; there were also memory effect between the structureâ… andâ…¡hydrate during process of the reformation. Based on the theory of hydrate reformation, the feasibility of storage carbon dioxid with method of hydrate is discussed from the aspects of dynamics and chemical thermodynamics.The memory effect between different structure hydrate in the process of reformation coincide the latest theory of "cage adsorption hypothesis".The research results have reference value for the studing and evaluating gas hydrate storage and transport,gas separation by using hydrate,exploitation of methane hydrate by using of carbon dioxide.