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Defining and quantifying gas hydrate transportability under multiphase flow based on a multiscale-multivariate approach

Chiarello, Conrado
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Advisor
Sum, Amadeu K.
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Date
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2024
Date Submitted
Keywords
crude oil
 flow assurance
 gas hydrates
 multiphase flow
 multivariate
 sponge model
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2024 - Mines Theses & Dissertations
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Chiarello_mines_0052E_12948.pdf
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Chiarello-HeavyOil-Emulsified-EM07-EM12.zip
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https://hdl.handle.net/11124/180696
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Abstract
Among flow assurance problems, hydrates have emerged as a major concern due to their propensity to form in subsea flowlines and quick plugging. While avoidance can be expensive, hydrate management warrants knowledge of transportability. There has been dissonance around the concept in literature, and efforts to simplify the problem often rely on one-dimensional criteria to represent a multivariate-multiscale phenomena. Moreover, authors and companies use different criteria to evaluate risk. In this work, a set of multidimensional criteria to evaluate slurry transportability is defined, encompassing all relevant components of risk (agglomeration, deposition, bedding, and viscosity), allowing for a conservative approach on gas hydrate management. Such components could be easily assessed through visual inspection, which is one of the key advantages of rock-flow cell reactors. The first step into addressing the problem was to validate the experimental setup, which was achieved through dispersion theory. Using a visual setup, droplet size and liquid-liquid flow patterns were studied, closely corresponding to data retrieved under similar conditions from flow loops. Next, the criteria are tested for in gas condensate systems with anti-agglomerants, where transportable slurries were produced for water cuts up to 50%. The results were summarized in a Slurry Phase Map, allowing for clear and concise representation of data while providing a multidimensional tool to predict gas hydrate transportability. The framework is extended to crude oil scenarios, where no low-risk slurry was seen and modes of failure were investigated: dispersed systems failed through viscosification and separate phases because of agglomeration, emphasizing dispersion state as a key variable to predict the limits of transportability. Finally, tests with wax were conducted to demonstrate the integration of different flow assurance problems into the existing framework. Wax deposition behavior was shown to be influenced by the presence of water and hydrates, and three patterns are reported: no deposition, cyclical, and homogeneous. A balance between flow shear and wax adhesion is proposed to explain such behavior. The presence of wax did not interfere in hydrate formation, and both solids were shown to individually account to the effective solid fraction when predicting slurry viscosity.
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