Measurement of Adhesion between Hydrate Particles and Solid Surfaces in a Condensed Water System

Gas hydrate formation and deposition in deepwater-oil and gas pipelines is a major threat to flow assurance. The adhesion between hydrate particles and the pipe wall is a key factor governing the hydrate deposition and blockage. Condensed water is ubiquitous on pipeline walls under practical operating conditions, yet its' influence on the hydrate formation and deposition remains unclear. In this study, the adhesion between cyclopentane hydrate particles and different carbon steel surfaces was studied in a micromechanical adhesion test apparatus. The adhesion behaviors of hydrate particles were compared on bare carbon steel, corroded carbon steel, epoxy-coated carbon steel, and epoxy-coated carbon steel with HKUST-1 loading, with emphasis on the roles of surface wettability and liquid bridges. The results show that the presence of condensed water increased the adhesion between hydrate particles and the wall from approximately 3.6 mN/m to 21.7-29.6 mN/m, depending on the corrosion degree of the surfaces. On epoxy-coated surfaces, the adhesion was reduced to 18.2 mN/m under the same condensed water condition, while further loading with HKUST-1 lowered it to 12.7 mN/m, representing a 30-57% reduction compared to uncoated corroded surfaces. The surface corrosion of carbon steel modified the wettability, which facilitated the retention of condensed water, resulting in the formation of a stable liquid layer on the surface of carbon steel. Thus, the liquid-bridge interactions were strengthened, and the adhesion was improved. When a liquid layer was present, the epoxy coating markedly reduced the adhesion by weakening liquid-bridge forces. On the surface of the epoxy coating, the further loading of HKUST-1 could reduce the thickness of the liquid layer, thereby reducing liquid-bridge forces and making the antiadhesion performance of carbon steel more stable. This work provides experimental evidence for selecting and designing surface-protection materials to prevent gas hydrate deposition and blockage in deepwater pipelines.