Abstract: In view of the problems of premature formation of CO2 hydrate at the bottom of well and excessive displacement resistance during percolation caused by liquefaction of CO2 under high pressure in the process of exploiting CH4 hydrate by CO2 displacement method, at the same time, in order to obtain high pressure and CH4⁃enriched product gas, mixture of CO2/CH4 was selected as injection gas to study "inhibitor⁃gas displacement" in core displacement device. It was found that when the concentration of CH4 in the injected gas was 57.4%, CH4⁃enriched (72.9%) gas product was obtained at 7.5 MPa. Meanwhile the amount of CH4 in the received gas product was significantly higher than that of the injected CH4. In addition, the effect of methanol solution with low volume fraction (20%) and CH4 mixture with high volume fraction (77.9%) on gas hydrate decomposition was also evaluated. The results showed that with the dissociation of methane hydrate during methanol and CO2/CH4 injection, the CH4 hydrate almost didn't decompose in the deep part of reservoir model, while the formation process of CO2 hydrate was still very significant.

Key words: Natural gas hydrates, Methane hydrate, Unconventional natural gas, Dioxide carbon；Thermodynamic - inhibitor, Gas hydrate exploitation, Core flooding

摘要： 针对CO2置换法开采CH4水合物的过程中CO2水合物在井底过早生成、高压下CO2发生液化导致渗流过程驱替阻力过大等问题，同时为了获得高压且富含CH4的产物气，选择CO2/CH4混合物作注入气，在岩芯驱替装置上研究了“抑制剂⁃气体置换法”分解CH4水合物的过程。结果表明，当混合气中CH4体积分数为57.4%时，可在7.5 MPa下获得体积分数为72.9%的CH4产物气，并且获得的CH4产物气的量要显著大于所注入的CH4的量。另外，还评估了在地层深部低体积分数的甲醇溶液（20%）和高体积分数CH4混合气（77.9%）对天然气水合物的分解效果，结果显示，随着“抑制剂⁃气体置换法”分解天然气水合物过程的进行，地层深部的CH4水合物基本不发生分解，但CO2水合物生成过程依然十分显著。

关键词: 天然气水合物, 　甲烷水合物, 　非常规天然气, 二氧化碳, 　热力学抑制剂, 　水合物开采, 　岩芯驱替