Hydrate Formation and Plugging Mechanisms in Different Gas–Liquid Flow Patterns

As oil/gas exploitation moves into deep water, hydrate formation and plugging in flowline have been a main concern of the flow assurance engineers. A series of experiments were conducted in a gas-emulsion multiphase flow system using a high pressure flow loop. The properties of hydrate agglomeration and deposition in different flow patterns were investigated. First, based on the hydrate chord length distribution and the changes of slurry density, several methods were proposed to quantitatively estimate the hydrate agglomeration degree and deposition degree. Second, typical results in each flow pattern were analyzed, and the plug formation mechanisms in each flow pattern were proposed. Then, after comparing the results in each flow pattern, it was found that the order of hydrate agglomeration degree from high to low is slug flow, stratified flow, bubble flow, and annular flow; and the order of hydrate deposition degree from high to low is annular flow, slug flow, bubble flow, and stratified flow.