(72d) Avoiding Flowline Plugging: Emulsion+Ice+Wax+Hydrate, the Beast Flow Assurance Discipline Must Confront | AIChE

(72d) Avoiding Flowline Plugging: Emulsion+Ice+Wax+Hydrate, the Beast Flow Assurance Discipline Must Confront


Bbosa, B. - Presenter, University of Tulsa
Waturuocha, A., University of Tulsa
Xu, H., The University of Tulsa
Solid generation and transportation in form of slurries has become one of the most important aspects of flow assurance engineering. Significant amount of work has been done in the past 40 years towards understanding and predicting the behavior of multiphase flow with solids; however, to date flow line plugging is still a challenge. There is no predictive tool available for use under all scenarios and there is still a lack of understanding of the interaction of the different flow assurance solids such as ice, wax and hydrates. To this list, emulsions should be counted as well since very high viscosity emulsions may stall flow.

This paper presents preliminary work done towards understanding system response with high viscosity emulsions. In addition to very high pressure losses, the systems are characterized by high shear heating effects. This means high temperature buildup in the areas of high shear such as close to the pipe wall. This phenomenon may be important in evaluating wax deposition since a negative radial temperature gradient is required. Four fluids were used to investigate this behavior and results showed that the temperature difference between the flowing fluid and the coolant in the annulus increased with fluid viscosity.


The second part of the paper presents pressure drop signature for hydrate transporting systems from fully dispersed to bedding onset to plugging. This section presents results from kerosene testing and examines factors affecting hydrate slurry transportation. Results showed that fully dispersed systems exhibit pressure drop curves running parallel to that of the carrier fluid. Onset on bedding was associated with pressure drop not changing with mixture velocity and occurred at a critical mixture velocity for a given hydrate volume fraction. Lastly, onset of plugging was characterized by increasing pressure drop with decreasing mixture velocity. For the low viscosity fluids, like kerosene, plugging results from solid fraction overburden in the system that the fluid cannot suspend.


The third part of the paper will discuss the effect of high viscosity emulsion on hydrate formation and transportability. Results showed that use of anti-agglomerants improves transportability of hydrates. For the high viscosity fluids, solids increase the slurry viscosity so high that the flowing mixture becomes mousse-like which eventually stalls the flow. This may be avoided by increasing the temperature of the flowing mixture.


Lastly, the paper will present preliminary work towards ice transportation, oil chemistry and hydrate morphology, and a review of the interactions of the different flow assurance solids.