Fundamental investigation of the adhesion strength between cyclopentane hydrate deposition and solid surface materials

Abstract

Hydrate agglomerations and hydrate depositions are two main processes that form hydrate plugging in deep-water oil and gas pipelines. Hydrate that directly grows and sinters on the pipe wall is an important hydrate-deposition case, which has been rarely studied. Understanding the adhesion strength of the sintered hydrate depositions is crucial in advancing the management of hydrate formation to avoid plugging in pipelines. In this work, a multi-spray method was first applied to form a hydrate-deposition layer on a solid surface. Further, the adhesion strength was measured using a self-built adhesion-strength measurement apparatus. The effects of subcooling, formation time, surface roughness, and material types on the hydrate-adhesion strength were investigated. The water content in the deposition was found to decrease with the increase in the subcooling and formation time, which led to higher adhesion strength. The adhesion strength was also significantly influenced by the surface roughness and material types, and surfaces with low roughness and strong hydrophobicity (i.e., high contact angle) resulted in lower adhesion strength. After obtaining the adhesion force, a model was developed to evaluate the feasibility of sintered hydrate deposition on the pipe wall in gas and oil systems. The simulation results revealed that the critical velocity required to remove the deposition would increase and decrease with the length and thickness of the deposition, respectively. Compared with the settling-down hydrate particle on the pipe wall, the required critical removal velocity for sintered hydrate deposition was much higher, which was beyond most of the pipeline operating conditions.