甲烷水合物生成过程中海水常量离子浓度的变化规律

The Concentration Changes of Major Ions in Seawater During the Methane Hydrate Formation Process

本文自行研制了一套甲烷水合物合成装置,模拟海洋环境甲烷水合物的生成过程,对该过程水合物生成位置、形态、反应时间、环境温压条件进行观测,同时连续测试体系海水中常量离子K+、Na+、Ca2+、Mg2+、Cl-、SO24-的浓度及海水盐度,探讨水合物生成过程的温压变化及离子浓度变化之间的关系和离子浓度的变化规律。结果表明,海水中甲烷水合物生成具有很大的随机性,在相同的初始条件下可能有不同的水合物成核、聚集过程;甲烷水合物在生成过程中,耗气量不断增加,孔隙水的盐度和海水中常量阴阳离子的浓度也在不断增加,这种变化具有较高的线性相关性(相关系数为0.9848～0.9950),且不受甲烷水合物生成位置及状态的影响;在水合物生成过程的微环境下耗气量相同时,离子浓度存在细微的差异。这些特征为通过测定海底水合物周围孔隙水中常量离子的浓度初步推算水合物的甲烷耗气量提供了依据。

A description of the synthetic experiment of methane hydrate is given in this paper, along with a preliminary study of ion concentration changes during the process, whilst providing important technical support for the gas hydrate geochemical exploration. In this article, the development of a set of experimental devices, which simulate the formation process of methane hydrate, is also discussed in this paper. The position and shape of hydrate, the reaction time, the temperature and pressure of the experiments were observed during methane hydrate formation. The concentrations of major ions including K＋, Na＋, Ca2＋, Mg2＋, CI-, SO＋- were continuously detected during the process to investigate the relationship among the major ion concentrations, temperature and pressure. The results show that methane hydrate forms randomly in seawater. It may have a different nucleation and agglomeration process of hydrate under the same initial conditions. There was a good positive linear relationship between the ions variation and methane gas consumption in the system with the correlation coefficients between 0. 9848 to 0. 9950, which was not affected by the formation position and morphology of the hydrate. The ion content had small differences under the same gas consumption in the microenvironment of the methane hydrate formation process. These important features provide the basis to make a preliminary estimate of gas consumption by using the major ion content in pore water around the methane hydrate.