(44c) Characterization of Gas Hydrates in Turbulent Two-Phase Flow Environment Using CFD: Tracking Deposition, Aggregation and Dissociation Effects

Prediction and mitigation of gas hydrates continue to dominate the research in the oil and gas community owing to their ability to substantiate severe production losses and risk issues in many gas and oil fields. As the industry looks towards more reliable modeling for risk assessment and flow assurance, numerical tools continue to expand as a major asset in the research and development for the prediction and mitigation of gas hydrates.

In this paper, we establish a numerical framework to model the formation and transport of hydrate particles in an oil-water pipeline with finite concentration of dissolved methane in a horizontal flow line. Multiphase flow of dispersed water and gas in an oil dominated pipeline is captured using an Eulerian multi-fluid modeling method while accounting for the exchange of mass, momentum and energy between different phases. In particular, formation and transport of hydrate particles generated as a result of dispersed water droplets interaction with the dissolved methane gas, under thermodynamically favorable condition, is tracked using a population balance model. The nucleation process is modeled as a heterogeneous reaction, with intrinsic kinetics, between the water and gas phases leading to finite size hydrate particles. Subsequent growth, aggregation and deposition of the hydrate particle and its influence on flow modulation such as flow jamming and blockage are captured in an extensive fashion. Based on the incoming gas composition, the hydrate formation threshold temperature is established. The effective viscosity of the oil-water is modeled

The current study explores the effect of different incoming gas compositions (effective hydrate formation temperature), water cuts and pipe sizing on the hydrate formation rates and the resulting pressure gradients across the flow line under consideration. Contour plots of hydrate fraction and their size distribution along with velocity and pressure distribution provide a detailed understanding of the flow physics associated with the hydrate formation process.