(29b) Modeling Hydrate Formation and Aggregation in Oil-Dominated Systems

Gas hydrates are ice-like solids, where hydrogen-bonded water molecules form cages surround light hydrocarbon gases (e.g., methane), typically at high pressure and low temperature. Hydrate formation can lead to operational and safety hazards in oil and gas production flowlines, Thermodynamic inhibition of gas hydrates is typically used to prevent the formation of these solids, but this method becomes prohibitively expensive as water production increases over the lifetime of the field. In recent years, the flow assurance aspect of hydrates has shifted from prevention to risk management, which requires a greater understanding of the formation and accumulation processes of hydrates in flowlines. One component to assess the impact of hydrates on flowlines is the impact of hydrates on flow properties. Here we present a model to capture transient oil-phase viscosification and pressure drop during hydrate formation and particle aggregation. The model is based on dynamic aggregation of particles, derived from cohesion force measurements between hydrate particles. This model captures transient effects of combined hydrate formation and aggregation. We also present a comparison of the model to several experimental datasets for hydrate formation and pressure drop collected at a large-scale industrial flowloop. The experiments were collected over a variety of water cuts (15-90 vol%), liquid loadings (50-90 vol%), and flow rates (1-3 m/s). Compared to previous models based on uniform aggregate size, the results show better predictions of the transient formation and aggregation behavior observed in flowloop experiments.