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Abstract A theoretical model based on static-force balance was proposed to describe the criteria of hydrate removal. Forces concerning particle-fluid and particle-surface interactions were involved. Extra adhesion brought by hydrates were considered and discussed. A comparison study was made between the current model and the hydrate removal model established in the literature and great agreement was found. The calculation revealed hydrate formed in the bulk gas phase would be removed. The difference between the model and the experimental observation in the literature may be explained by the sintering effect, which is not included in the model. This model may provide a helpful guideline to estimate the threshold mean flow velocity needed to maintain the safety of gas transport. [ABSTRACT FROM AUTHOR]

[Display omitted] • An improved model for hydrate particles removal from surface is proposed. • Hydrate particle diameter influencing the critical velocity than the initial liquid bridge volume. • Hydrate particles decomposition happening in the removal process. Understanding the critical velocity at which hydrate particles can be removed from a solid surface is crucial for flow assurance issues. An improved model is proposed to predict the critical velocity in hydrate particle removal process by considering a deformed liquid bridge. In situ experiments were performed for validation, and it was observed that hydrate particle decomposition occurred during the removal process. The particle diameter was determined to be a more dominant factor influencing the critical velocity than the initial liquid bridge volume. The resulting confidence level was 95% within a 30% error, showing its robust capability for engineering applications. [ABSTRACT FROM AUTHOR]

With the gradual advancement of oil and gas exploration into deep offshore, the hydrate blockage has emerged as a critical concern for the flow assurance. We conducted constant-velocity hydrate formation and variable-velocity rheology experiments with a novel visual-loop to analyze slurry flow and viscosity change in pipelines. Results showed staged pressure variations during hydrate formation-aggregation-deposition process, and it could be analyzed judiciously with a developed viscosity model. Initially, hydrates dispersed as small flocculent particles with minor aggregation, gradually raising differential pressure, and the critical viscosity model parameter, hydrate aggregation rate (m) was <1. Subsequently, particle aggregation and wall adhesion dominated, resulting in reduced hydrate flow volume and possible blockage of special pipelines (e.g., dead-leg), with m -values >1. Finally, as hydrate growth continued, substantial adhesion to the pipeline reduced flow diameter, significantly increasing blockage risk. However, the addition of sufficient surface-active ingredients improved hydrate dispersibility and enabled the slurry to maintain the first stage, exhibiting long-term stability with an m -value <1. Additionally, the apparent viscosity of the hydrate slurry within the pipeline was accurately determined utilizing a novel approach, accounting for its yield-pseudoplastic behavior. The calculated viscosities closely matched post-sampling rheometer measurements, and were effectively predicted by the developed viscosity model. [Display omitted] • Hydrate formation and rheology experiments were conducted in a visual-loop. • The hydrate formation-aggregation-deposition process was analyzed. • Hydrate aggregation and the blockage risk were characterised by the model. • The viscosity was determined accounting for its yield-pseudoplastic behavior. • The hydrate slurry viscosity was effectively predicted by the developed model. [ABSTRACT FROM AUTHOR]