含水合物沉积物合成方法及其对热、力学性质影响的研究进展

研究含水合物沉积物的热学和力学性质对保障天然气水合物的有效安全开采具有重要和应用意义。鉴于现场保压取样研究非常困难,目前常用的方法是利用实验室人工合成含水合物沉积物样品进行试验。首先总结了孔隙填充型、骨架(颗粒)支撑型、胶结型和颗粒包裹型的水合物在沉积物中的4种常见生长模式,以及不同生长模式下含水合物沉积物物理性质的差异;然后,介绍了溶解气法、部分水饱和法和种冰法3种实验室水合物合成方法及其对水合物生长模式的影响;最后,指出含水合物沉积物的热学性质和力学性质受到水合物饱和度、水合物生长模式等因素的综合影响,而水合物饱和度又受到水合物合成方法和水合物形成物的影响。因此,在开展实验研究过程中,应根据研究目的,选择合适的水合物形成物和水合物合成方法,以使得实验结果能够更好符合实际情况,从而指导生产实践。

Progress on Laboratory Synthetic Methods, Thermal and Strength Properties of Gas Hydrate Bearing Sediments

The safe and high-efficient exploitation of gas hydrate is one of great concerned problems in gas hydrate research. Changes in the thermal and strength properties of gas hydrate bearing sediments (GHBS) will occur during gas hydrate dissociation. Due to the hydrate existence under the deep marine setting and P-T condition, there are many challenges to investigate the mechanical and thermal properties of in-situ GHBS. However, synthesizing GHBS in laboratory is a trend. The four main growth patterns, such as pore filling, load bearing, cementing and grain coating hydrates in sediments are summarized and the different physical properties of GHBS in different growth modes are discussed. In this paper, three hydrate synthesization methods, including dissolved gas method, partial water saturation method and ice-seeding method, and the advantages and disadvantages are presented. Generally, different synthesizing methods will lead to different hydrate growth patterns, and the thermal and strength properties of GHBS are affected by hydrate saturation and hydrate growth pattern, meanwhile hydrate saturation is also affected by hydrate synthesizing method and hydrate types. Therefore, appropriate hydrate types and hydrate synthesization methods should be selected for different experimental purposes, and then the results can be compared with actual situation and applied to the hydrate production practice.