石英砂中甲烷水合物稳定条件研究

Stable Conditions for Methane Hydrate in Quartz Sand

采用不同粒径(160～200目、200～300目、300～400目、400～600目)细颗粒石英砂模拟自然界中沉积物实验合成甲烷水合物,采用多步升温分解法测定了甲烷水合物的稳定温度-压力(p～T)条件.结果发现细颗粒石英砂对甲烷水合物的稳定条件有明显影响,温度最大下降1.5 K.其中160～200目的石英砂是实验测试条件下石英砂对甲烷水合物稳定条件有无影响的分界目数.每一种石英砂在不同的温度压力下甲烷水合物p-T数据点较为离散,并且不同石英砂中p-T数据曲线出现交叉,这与文献中采用规则的硅胶、玻璃球等测得的结果有所不同.文献中测定的甲烷水合物p-T数据点温度相对于纯水中甲烷水合物p-T数据点温度向左偏移量相同.

Abstract Methane hydrate were synthesized in fine quartz sand with different size （160～ 200 mesh, 200～ 300 mesh, 300～ 400 mesh, 400～ 600 mesh） to determine the stable temperature-pressure conditions （p-T） for methane hydrates using step-heating decomposition method. The results showed that fine particles of quartz sand significantly affect methane hydrate stable conditions, of which 160～ 200 mesh quartz sand is the boundary mesh one whether the p-T conditions for methane hydrate is different or not under experimental tests. The maximum temperature difference for stable conditions of methane hydrates is 1.5 K between fine quartz sand and bulk water. For each of fine particles of quartz sand, the p-T data of methane hy- drates is discrete at different temperature and pressure, and p-T data curves intersected in different quartz sand. This is different with the results in the literatures simulated with silica gel or glass bead. In the literatures, the p-T data curve shifts to the left at the same extent.