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The major parameters for a hydrate slurry flow model are suggested. A field trial in a once-through pipeline indicated a significantly confined operating region without plugging. The implication of these results is that current versions of hydrate cold flow will need to address hydrate film growth and deposition on pipewalls. Flow loop tests alone do not simulate the extent of plugging because of film growth or deposition. A unique learning in this work is that emulsified droplet distributions were measured as a function of watercut, surfactant concentration, and fluid velocity. Droplet size and droplet size distribution increased with an increasing watercut below the inversion point. Droplet size and droplet size distribution decreased with an increasing surfactant concentration. An increasing surfactant concentration limited wall deposits to some extent. An increasing fluid velocity reduced wall deposits and hydrate slurry viscosity. Wall deposits decreased with a decreasing gas void fraction.

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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.

The growing use of natural gas, cleanest of all available fossils fuels, is already raising concern regarding the long-term supply of this precious resource. The amount of methane in gas hydrates is much greater than all other presently known sources of methane. This paper describes some fundamental challenges, the location, magnitude, and feasibility of recovery, which must be addressed to recover methane from dispersed hydrate sources. For methane recovery, we briefly describe kinetic models of methane hydrate decomposition for temperature and pressure conditions that mimic in situ methane hydrate stability. We also propose the catalytic role of sediment impurities, if any, in inducing nucleation sites for hydrate formation. The availability of plentiful methane is important to avoid future energy crises, such as that which crippled the world economy three decades ago.