Abstract:

Traditional depressurization method is easy to encounter the slow heat transfer rate of stratum, and thus the system temperature and pressure maintain a phase equilibrium condition for a long period, which seriously prolongs the production time. To solve the slow hydrate decomposition rate in the low temperature area during depressurization, three-dimensional simulation of natural gas hydrate production by inhibitor injection method was carried out to obtain the law of hydrate decomposition and gas production. The effect of inhibitor injection and soaking process on hydrate decomposition was comprehensively analyzed on the basis of temperature and pressure change. The results showed that the inhibitor injection method could significantly speed up the efficiency of hydrate decomposition during injection period, however, large injection volume and multiple-time injection were easy to cause plugging and prolong the production time. Compared with the small-sized experimental device, the inhibitor had been fully migrated in the injection stage due to the long injection time in the pilot-scale experiment, therefore, the soak time should be about 40minutes.

Key words: hydrate, exploitation, inhibitor injection, pilot-scale device

摘要：

单纯降压法开采天然气水合物容易遇到地层传热速率慢的问题导致体系温度压力长期处于相平衡状态，因而严重拉长了开采时间。为解决降压法开采过程中低温区域水合物分解过慢的问题，本文利用三维装置研究了注化学剂法开采过程中水合物分解和产气规律。根据反应釜内温度和压力的变化，全面分析了注入过程、焖井过程对水合物分解的影响。结果表明，对于单井吞吐法，在注入抑制剂阶段可以刺激水合物快速分解，但不宜采用过大的注入量和过多的注入次数，过大的注入量和注入次数会增大堵塞风险导致开采时间被大大延长。相较于小型实验装置，中试级别实验由于注入时间长，抑制剂在注入阶段已经得到较为充分的运移，因而焖井时间不能过长，控制在40min左右为宜。

关键词: 水合物, 开采, 注抑制剂, 中试装置