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A MODELING APPROACH TO HYDRATE WALL GROWTH AND SLOUGHING IN A WATER SATURATED GAS PIPELINENicholas, Joseph W., Inman, Ryan R., Steele, John P.H., Koh, Carolyn A., Sloan, E. Dendy 07 1900 (has links)
A hydrate plugging and formation model for oil and gas pipelines is becoming increasingly important as producers continue to push flow assurance boundaries. A key input for any hydrate plugging model is the rate of hydrate growth and the volume fraction of hydrate at a given time. This work investigates a fundamental approach toward predicting hydrate growth and volume fraction in a water saturated gas pipeline.
This works suggests that, in the absence of free water, hydrate volume fraction can be predicted using a wall growth and sloughing model. Wall growth can be predicted using a one-dimensional, moving boundary, heat and mass transfer model. It is hypothesized that hydrate sloughing can be predicted when a coincident frequency exists between hydrate natural frequency and flow induced vibrations over the hydrate surface.
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Experimental Investigation of Deposition and Wall Growth in Water Saturated Hydrocarbon Pipelines in the Absence of Free WaterNicholas, Joseph W., Dieker, Laura E., Nuebling, Lee, Horn, Bob, He, Helen, Koh, Carolyn A., Sloan, E. Dendy 07 1900 (has links)
Using a combination of micromechanical force and flowloop measurements, hydrate deposition on a pipe wall surface was investigated for ‘dry’ hydrates formed in the bulk phase and for hydrates growing on the pipe surface.
Cyclopentane ‘dry’ hydrates (without a free water phase) were used to predict whether hydrates, formed in a bulk condensate phase, would adhere to a pipe wall. Adhesion forces between cyclopentane hydrates and steel were measured using a micro-mechanical force apparatus. The average force of adhesion was measured to be very small, less than 0.01 N/m. This force was used in a particle force balance, predicting that hydrates formed in the bulk phase would not deposit on the pipe wall.
It was hypothesized than in the presence of a water saturated hydrocarbon, hydrates would grow on the pipe wall as the fluid cooled below its equilibrium temperature. This hypothesis was confirmed using a single pass condensate flowloop. Water was continuously dissolved into the flowloop inlet stream as water deposited in the flowloop test section, resulting in both a pressure drop and fluid temperature increase. This work illustrates the need for a hydrate wall growth model.
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