多孔介质中CO2-CH4水合物置换过程的强化方法研究进展

CO2置换天然气水合物中的CH4是一种非常有前途的天然气水合物开采方法，该法兼具能源安全开采和温室气体地层封存的双重优势。首先综述了多孔介质中CO2-CH4水合物置换的研究进展，分析了制约CO2置换法开采天然气水合物商业应用的关键瓶颈问题，即置换过程存在的反应周期长、速率慢和效率低等问题。针对此问题，主要详述了强化CO2-CH4水合物置换的强化方法研究进展，包括注入不同的CO2相态、小分子及混合气体的强化、结合传统开采法的联合强化以及其他强化方法的作用机理，讨论了各种强化方法尚待完善和改进的地方。最后提出了多孔介质中CO2-CH4水合物置换强化方法目前研究的不足和未来的研究方向。

Research progress of enhancement methods of CO2-CH4 hydrate displacement in porous media

CO2 replacement of CH4 from natural gas hydrate is a very promising method to exploit natural gas hydrate, this method has the dual advantages of energy safe exploitation and greenhouse gas formation storage. Firstly, the research progress of CO2-CH4 hydrate displacement in porous media is reviewed and the key bottleneck problems, such as long reaction cycle, slow rate and low efficiency, which restrict the commercial application of CO2 displacement method to the exploitation of natural gas hydrate, are analyzed. In view of this problem, the research progress of strengthening methods for CO2-CH4 hydrate replacement in porous media is comprehensively reviewed. It includes the enhancement of liquid CO2, the enhancement of small molecules such as N2 and H2, the enhancement of prolongation of reaction time, the enhancement of application of adsorption materials with both CO2 and CH4 gas absorbability and the analysis of new ideas enhanced mass transfer during displacement due to the formation of porous CO2 hydrate. At the same time, the characteristics of various strengthening methods are analyzed. Primarily, different phase states of CO2, small molecules and mixed gases reinforcement replacement and the mechanism of other reinforcement methods are described in detail, and the improvement of various reinforcement methods is discussed. Studies show that, for the overall recovery rate, replacement combined with conventional methods is more effective than introducing small molecule mixture and changing the injected phase state of CO2. Therefore, the combined enhancement of the single method is an effective way to improve the replacement efficiency. Finally, the shortcomings of the current research and the future research direction of the enhancement of CO2-CH4 hydrate displacement process in porous media are proposed.