Gas Hydrate Production Technology for Natural Gas Storage and Transportation and CO2 Sequestration

摘要

Gas hydrates (or clathrates) are group ice-like crystalline compounds, which form through a combination of water and suitably sized 'guest' molecules under low temperature and elevated pressure conditions. Within the clathrate lattice, water molecules form a network of hydrogen-bonded cage-like structures, enclosing the guest molecules, which generally comprise of low-molecular diameter gases (e.g., methane, ethane, propane, carbon dioxide (CO2), etc). Although hydrate formation can pose serious flow assurance problems in oil and gas industry, gas hydrates have great potential for positive applications - turning a long standing problem into a potential benefit. Two important properties of hydrates are their very high gas to solid ratio, 1m~3 of hydrate may contain up to 175m3 of gas (at standard conditions), and self preservation effects which make them feasible to be transported at atmospheric pressure. They thus present a novel means for gas storage, transportation and delivery, with consequent potential applications in a wide variety of areas, including exploitation of remote gas fields, CO2 sequestration, etc. However, a major barrier to the development of hydrate technology is the current lack of an economical means for the mass-production of solid hydrate in a manageable form. In this communication, a literature review with a critical evaluation has been conducted on the various reported hydrate production techniques to better understand the production process and identify any shortcomings of such techniques. In addition a new technique is proposed to produce hydrate in which dry hydrate is formed in especially designed reactor in the presence of excess gas. The technique has been applied to production of NG hydrate for NG storage and transportation purposes and CO2 hydrate for application in CO2 sequestration. The preliminarily promising results of series of tests carried out on a NG and CO2 hydrate formation are presented along with an evaluation of atmospheric hydrate self-preservation and dissociation rate versus time and temperature.