Study on Growth and Deposition and Mechanical Properties of Hydrate in the Presence of Silty Sand.

The safe exploitation and transportation of hydrates are seriously threatened by hydrate growth and deposition in the flow channel. However, silt impurities are inevitably present in the exploitation flow channels. This article aims to clarify how slit impurities affect hydrate growth, deposition, and mechanical properties. The process of hydrate growth and deposition in the presence of silty sand on the pipe walls of different solution systems and pipe wall materials was investigated. The results indicated that, in the deionized water system for both metallic pipe wall and nonmetallic pipe wall, and in the sodium dodecyl sulfate (SDS) solution system for metallic pipe wall, the hydrate growth rate increased by 131.48, 114.76, and 84.89%, respectively, after adding a 9.0% volume fraction of silty sand. Additionally, the adhesion strength between the hydrate and pipe wall at different silty sand contents was measured. It was found that the adhesion strength ranged from 140.61 to 234.64 kPa. With an increase in the silty sand content, the adhesion strength first increased and then decreased, reaching a maximum when the silty sand volume fraction was 3%. With the extension of the hydrate formation time, the adhesion strength increased by up to 57.62%. Furthermore, the mechanism of hydrate growth in the presence of silty sand was proposed. The hydrate growth in the SDS solution system differed from that in the deionized water system. In the presence of SDS, no dendritic hydrate was observed around the generated hydrate, while dendritic hydrates were observed around the hydrates in the deionized water systems with different pipe wall materials, with more dendritic hydrates forming in the metallic pipe wall. After addition of silty sand, the initial position of hydrate formation shifted from the interior of the droplet to the silty sand inside the droplet. This work provided data support for preventing hydrate plugging in the flow channel and was of great significance for ensuring the safe production of hydrates.