“CH4-CO2”置换法开采天然气水合物

天然气水合物作为一种储量巨大的清洁能源,其开采价值已引起越来越多的关注。当前天然气水合物开采技术仍不足以商业化应用,还需进一步的实验研究进行理论支撑。二氧化碳置换开采天然气水合物被认为是能同时实现天然气水合物开采与二氧化碳减排、封存的双赢技术,近年来得到了较广泛的研究。置换过程中,混合天然气水合物的热力学和结构性质是预测含水合物沉积物中的热流和水合物解离所需的热量以及评估水合物储层的CO₂储存能力的关键因素。本综述在调研国内外天然气水合物开采技术研究现状的基础上,围绕CO₂置换开采天然气水合物的热力学特性、微观机理与置换效率等,总结了各研究取得的成果,针对置换研究中存在的问题进行了分析,认为当前置换法开采天然气水合物最关键难点在于提高置换效率,而解决该问题的根本在于从热力学和动力学角度弄清楚置换反应的微观机理及控制性因素,明确置换机理,从而在未来的研究有的放矢。

Research Progress on the Micro-Mechanism and Efficiency of CH4-CO2 Replacement and Extraction of CH4 Hydrate

As a kind of clean and non-renewable energy with huge reserves, natural gas hydrate has attracted more and more attention for its value in exploitation. But so far, the exploitation of natural gas hydrate is still in the conceptual and experimental research stage, and the current exploitation technology of natural gas hydrate is still inadequate from commercial application, which is constantly developing. Methane-carbon dioxide (CH₄-CO₂) replacement and extraction of natural gas hydrate is considered to be a win-win technology that can simultaneously realize natural gas hydrate extraction and carbon dioxide emission reduction and storage, and has been extensively studied in recent years. During the replacement process, the thermodynamic and structural properties of mixed gas hydrates are the key factors for predicting the heat flow in hydrate deposits and the heat required for hydrate dissociation, as well as evaluating the CO₂ storage capacity of hydrate reservoirs. On the basis of investigating the current research status of natural gas hydrate mining technology at home and abroad, this review focuses on the thermodynamic characteristics, microscopic mechanism and replacement efficiency of CO₂ replacement in natural gas hydrate extraction, and objectively evaluates current research and summarizes the results of each research. By the review, we put forward scientific suggestions for the problems in the replacement research, and pointed out a reasonable direction for future research.