Characterizing Methane Hydrate Formation in Horizontal Water-Dominated Bubbly Flow

Abstract

Methane hydrate formation in water-based drilling mud is the great important issue for well control during the drilling operation in deep-water environment. However, most of researchers focus on hydrate formation in oil-dominated system and gas-dominated system. Few researchers pay enough attentions to hydrate formation in water-dominated system, especially for bubbly flow. In this work, groups of experiments of methane hydrate formation in horizontal water-dominated bubbly flow are performed at liquid fluid velocities of 0.95 to 1.4m/s and void fractions from 2.5% to 5.0%. According to experimental observations, methane hydrates does not form hydrate shells on gas bubbles in bubbly flow and no complete hydrate shells or plates are observed in experiments. Hydrate particles formed on the surface of bubbles prefers to slough off immediately by high motion of liquid fluid, which results in appearance of tiny bubbles in flow loop. According to analysis of the reaction rate factor, the intrinsic kinetic mainly dominates the hydrate formation at the high subcooling condition but the mass transfer dominates the hydrate formation at the low subcooling condition. A hydrate kinetic model is developed for the horizontal water-dominated bubbly flow, as a function of reaction rate factor, liquid fluid velocity, subcooling temperature and interfacial area. In the new model, the multiphase flow concept of interfacial area concentration is firstly brought in predicting interfacial areas for methane hydrate formation in bubbly flow. Another 8 groups of hydrate formation experiment are conducted to validate the new model and the maximum discrepancy is less than 8%.Ppa