热力学抑制剂与CO_2同注开采天然气水合物的实验研究

Simultaneous injection of thermodynamic inhibitors and CO_2 to exploit natural gas hydrate: An experimental study

为解决CO_2置换法开采天然气水合物(以下简称水合物)过程中出现的置换速率慢、置换程度不高等问题,提出了将CO_2置换法与热力学抑制剂法组合使用的技术思路,即"抑制剂—置换法"。在实验室利用填砂管模型在岩心驱替装置上测定了CO_2与不同浓度的甲醇溶液在同注的情况下CH_4水合物的分解效果。结果表明:(1)甲醇的浓度对水合物开采效果起着决定性作用,甲醇溶液浓度越小,CH_4水合物的分解越弱,其变化趋势表现为以CH_4水合物的分解为主导转变为以CO_2水合物的生成为主导;(2)当CO_2与浓度为20.8%的甲醇溶液同注时,主要发生CH_4水合物的分解,CO_2水合物几乎不生成;(3)当CO_2与浓度为15%的甲醇溶液同注时,既发生CH_4水合物的分解,也发生CO_2水合物的生成;(4)当CO_2与浓度为10%的甲醇溶液同注时,CH_4水合物几乎不分解,主要发生CO_2水合物的生成。结论认为,"抑制剂—置换法"可促进CH_4水合物的分解,提高其开采效率。

When the CO2 replacement method is used to exploit natural gas hydrate （NGH）, the replacement rate and the replacement degree are both low. In view of this, this paper proposed an inhibitor-replacement method, with the technical idea of combining the CO2 replacement method with thermodynamic inhibitor method. The dissociation results of CH4 hydrate, while CO2 and methanol solutions with different concentrations were injected simultaneously, were experimentally measured in a core displacement device by using the sand packed tube model. And the following experimental results were obtained. First, the concentration of methanol solution plays a decisive role in NGH exploitation. The lower the concentration of methanol solution, the weaker the dissociation of CH4 hydrate. And it is dominantly transformed from the dissociation of CH4 hydrate to the generation of CO2 hydrate. Second, when a mixed CO2–methanol solution with a concentration of 20.8% is injected simultaneously, the main process is the dissociation of CH4 hydrate, and CO2 hydrate is hardly generated. Third, during the simultaneous injection of the mixed solution with a concentration of 15%, CH4 hydrate is dissociated and CO2 hydrate is generated. And fourth, When CO2 is injected simultaneously together with the methanol solution with a concentration of 10%, the generation of CO2 hydrate is dominant, and CH4 hydrate is hardly dissociated. It is concluded that the proposed inhibitor-replacement method can promote the dissociation of CO2 hydrate, increasing its exploitation efficiency.