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天然气水合物是分布在海洋和大陆多年冻土中的一种具有巨大商业开发价值的新型战略性替代能源。同时,含天然气水合物地层中水合物的分解将带来严重的地质灾害和气候问题的关注。试验室内开展含天然气水合物沉积物物理力学性质研究需要首先解决的是制样问题,即在试验室内快速形成符合现场原位形成模式的试样,并且水合物均匀分布于土样孔隙中。海洋天然气水合物主要是在扩散体系中形成的,即溶解在水中的气体以扩散迁移的方式进入温压条件适合的地层内与水结合生成天然气水合物。文中试验方法与装置利用高压恒流泵驱动溶有气体的去离子水在土样中循环,采用磁力搅拌装置加速和增大气体在水中的溶解,使土样在较短时间内被溶气水饱和,然后将土样温度降低至与气体压力相对应的相变温度以下后,溶于水中的气体与水结合生成水合物析出,且均匀地填充土样孔隙中。采用粉土和CO2气体试验表明,制得含水合物沉积物大约需1 d的时间,通过观察和测试含水率证明,所制得试样具有良好的均匀性,解决了目前在试验中采用的制样方法所制得的试样中水合物分布不均匀以及水合物形成时间过长的问题,为进一步开展含天然气水合物沉积物物理力学试验提供了技术保证。
Gas hydrates are a new type of strategic alternative energy of great commercial value distributed in the permafrost of oceans and continents. At the same time, the decomposition of hydrates in gas hydrate-bearing formations will cause serious geological disasters and climate concerns. The research on the physical and mechanical properties of gas hydrate-bearing sediments in the laboratory needs to solve the problem of sample preparation first, that is, rapid formation of a sample conforming to the in-situ formation mode in the laboratory and the hydrate uniformly distributed in the soil-like pores. The marine gas hydrate is mainly formed in the diffusion system, that is, the gas dissolved in water enters the formation suitable for temperature and pressure conditions and combines with water to generate gas hydrate in a diffusion-migration manner. In this paper, the test methods and devices using high-pressure constant current pump driven gas dissolved deionized water circulating in the soil sample, the use of magnetic stirring device to accelerate and increase the gas dissolved in water, so that soil samples in a relatively short period of time dissolved gas water Saturated, and then reduce the soil temperature to below the phase transition temperature corresponding to the gas pressure, the water dissolved in the water combines with water to form hydrate to precipitate and uniformly fill the soil-like pores. Experiments using silt and CO2 gas showed that the hydrate-bearing sediment preparation took about 1 day, and the moisture content of the sample was observed and tested to show that the resulting sample had good homogeneity and solved the problems currently used in the test The problem of inhomogeneous hydrate distribution and long hydrate formation time in the sample prepared by the sample preparation method provides technical assurance for further carrying out physical and mechanical tests of gas hydrate-bearing sediments.