三轴应力下CO_(2)置换开采天然气水合物实验研究

EXPERIMENTAL STUDY ON CO_(2)REPLACEMENT-EXPLOITATION OF NATURAL GAS HYDRATE UNDER TRIAXIAL STRESS

为模拟海域真实环境,在三轴应力、氯化钠体系以及水合物储层富水状态的条件下,开展针对氯化钠体系、储层初始饱和度以及置换压应力对液态CO_(2)置换开采海域天然气水合物的实验。研究表明:在三轴应力以及孔隙度约46.70%的条件下,氯化钠体系对CH4置换效率影响较小,但对CO_(2)水合物合成表现出抑制作用;储层初始饱和度与CH4置换效率之间是负相关关系且高的储层含水率更有利于CO_(2)封存;CH4置换效率随着置换压应力的增长有一定幅度的提高,置换压应力的增大为CO_(2)水合物合成提供了高的驱动力,进而提高了CO_(2)封存效率。

In order to simulate the real environment in the sea area,these experiments were carried out to study the effects of sodium chloride,initial saturation of the reservoir and replacement compressive stress on the liquid CO_(2)replacement-exploitation of natural gas hydrate in the sea area under the rich water condition.This study shows that under the condition of triaxial stress and porosity about 46.70%,the sodium chloride system has little effect on the CH4 replacement efficiency,but it inhibits the CO_(2)hydrate synthesis.There is a negative correlation between initial reservoir saturation and CH4 replacement efficiency.In addition,a high reservoir water content is more favorable for CO_(2)storage.The CH4 replacement efficiency increases with the increasing replacement compressive stress,the increase of replacement compressive stress provides a high driving force for the CO_(2)hydrate formation,thereby improving the CO_(2)sequestration efficiency.