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A hydrate directly growing and sintering on a pipe wall is an important hydrate deposition case that has been relatively unexplored. In the present study, the adhesion strengths of a sintered cyclopentane (CyC5) hydrate deposit under different solid precipitation and surface corrosion conditions were measured and discussed. It was found that the hydrate adhesion strengths increased by 1.2–1.5× when the soaking time of the carbon steel substrate in a 5 wt % NaCl solution increased from 24 to 72 h, which reduced the water wetting angle from 112 ± 3.5° to 94 ± 3.3°. The wax coating reduced the strength of CyC5 hydrate adhesion by up to nearly 20-fold by reversing the substrate wettability and affecting the hydrate morphology. The measurements performed on scales indicate that calcium carbonate scales strengthen the adhesion strength because of the decrease in the water wetting angle. In addition, honeycomb holes on the surface reduce amplification. Furthermore, settling quartz sand on the wall reduced the adhesion strengths by decreasing the effective sintering area of the hydrate on the underlying base. Finer sand and higher concentrations led to lower strengths. On the basis of the verified linear correlation between the hydrate adhesion strength and the adhesion work of droplets on different substrates and the influence of water conversion during deposition, both an equation and a key constant parameter were obtained to predict the sintered hydrate deposit adhesion strengths on substrates.

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The presence of unconverted water drops in bulk hydrocarbon is likely to bridge hydrate particles and cause hydrate agglomeration, leading to hydrate accumulation or bedding in oil and gas pipelines. The knowledge of the interaction forces between hydrate particles and water drops can provide critical insights into hydrate agglomeration as well as potential prevention strategies. At high subcooling, the frequent solidification of the capillary bridge between hydrate particles could significantly affect the interaction force. However, the existing classic pendular liquid bridge model with a fixed liquid volume is not adequate for this unique case. A new interaction force model is required. Based on the pendular liquid bridge model and hydrate shell theory, a modified interaction force model was developed by considering the solidification of capillary bridges. Furthermore, using a self-built micromechanical force apparatus, the cyclopentane (CyC5) hydrate−droplet adhesion forces at a temperature range from 0.5 to 6 °C were measured to verify the proposed model. The experiments suggest that as the temperature was increased from 0.5 to 6 °C, the adhesion forces first increased and then decreased. Solidification could enhance the strength of the already formed liquid bridge. However, at lower temperatures (0.5−3 °C), the quick solidification led to smaller particle/bridge initial contact areas and weaker adhesion forces. By accurately predicting the evolution of the capillary bridge shape/outline, the predicted adhesion forces agree well with the experimental measurements. This study can provide more insights into hydrate agglomeration. The proposed model is an important supplement to hydrate adhesion theory and could more accurately evaluate hydrate plug risks in gas−oil flowlines.