Quantitative Framework for Hydrate Bedding and Transient Particle Agglomeration

Abstract

Hydrate bedding is defined as the gravitational segregation of hydrate particles, leading to their accumulation at the bottom of the pipe. Previous research has shown that hydrate bedding is a physical mechanism that potentially can cause blockage formation in pipelines. The data analysis from highpressure flow loop experiments indicated that hydrate bedding could lead to increasing pressure drop, decreasing hydrate particle transportability, and increased risk of plugging. Despite the importance, reliable quantitative models to predict the occurrence of hydrate bedding under transient agglomeration conditions are currently lacking. In this work, we propose a hydrate bedding framework that combines the modeling of particle agglomeration under dynamic conditions with a critical velocity model to predict the onset of hydrate particle bedding. By applying the population balance approach, the new framework generates a distribution of hydrate agglomerates as a function of particle concentration, mixture velocity, and physical properties of the continuous phase. The distribution of agglomerates is then divided into two parts: one part contains sizes larger than the critical size (bedding), and the second part contains sizes smaller than the critical size (suspension). With this new approach, the combined bedding-agglomeration framework predicts the onset of hydrate particle bedding with reasonable accuracy for experiments performed at a high-pressure flow loop. Potentially, this framework can be integrated in transient multiphase flow simulators to compute pressure losses and manage risks due to hydrate bedding.

Behavior of Methane Hydrate-in-Water Slurries from Shut-in to Flow Restart

“…Conversely, in Experiment 1, the applied stress was increased only linearly (Figure ). This slower increase may have resulted in a mixture of flowable small agglomerated hydrate particles and stagnant large ones in the flowloop (Figure , left) because of the different deposition velocities associated with particles of different sizes . This may then result in small particles becoming trapped in the regions filled with larger static structures, which may be associated with a small-scale jamming-type event: jamming/clogging often occurs in the regions with a decreased cross section (Figure , right). − If this occurs, small particles will increase the local hydrate volume fraction in stagnant regions, leading to a rise in the yield stress required to clear the new, more severe blockage.…”

“…When the hydrate slurry has started to move, the continuous structure may be broken into relatively large agglomerated hydrate particles, and these may be more easily deposited. In a recent study, Srivastava et al 31 proposed a hydrate bedding process for oil-dominant systems which incorporates the size distribution of aggregated hydrate particles and the deposition velocity of Turian et al, 32 which increased with an increase in the particles' size. Their approach provided a reasonable prediction of hydrate bedding as observed in their flowloop experiments.…”

Performance of Waterborne Polyurethanes in Inhibition of Gas Hydrate Formation and Corrosion: Influence of Hydrophobic Fragments

“…Hydrate particles may agglomerate, which results in hydrate plug and pipeline blockage. This impedes the fluids flow, thereby reducing transportation efficiency, increasing operating costs, as well as contributing to an industrial accident in extreme cases [2,3]. In addition, acidic environment can cause severe corrosion of the pipeline or other contact steel elements used in the production, transportation, storage, and refining of hydrocarbons, which reduces their service life (pipelines, etc.).…”

Hydrate Risk Management in Gas Transmission Lines

“…First, estimation of interparticle cohesive forces must incorporate unconverted water, as first proposed by Fidel-Dufour, to correctly inform the dynamic force balance on a fractal aggregate. , Introducing both water–hydrocarbon and hydrate–hydrocarbon surface free energies in the simulation environment, in preference to using a hydrate contact angle that can be challenging to interrogate in the laboratory, further provides the ability to directly capture the effect of hydrate-active surfactants in the system. , Second, the refinement and application of a fit-for-purpose slurry viscosity model to describe hydrate-in-hydrocarbon systems was critical to correctly representing frictional pressure loss, with approaches proposed by both Majid et al , and Qin et al − that significantly improve upon the original basis from Mills . Third, the consideration of both moving and stationary bed phases, as originally hypothesized by Hernandez, is critical to correctly estimating the magnitude of frictional pressure loss observed for systems with either partial dispersion of water in the liquid hydrocarbon phase ,− or comparatively low flowing shear stress, as reported by Srivastava and co-workers − and recently demonstrated by Qin et al and Wang and co-workers. ,, Fourth, improving the accuracy of hydrodynamic slug flow behavior, both without and during hydrate formation, has been demonstrated by Zerpa et al to be a critical development path for the continued improvement of the mechanistic description of hydrate blockage formation.…”