Insight into the plugging mechanism in water-continuous hydrate slurries

Oil-water-gas co-transport often occurs in offshore oil/gas production, in which gas hydrate formation could lead to severe flow assurance issues and subsequent safety and environmental risks. As the offshore oil/gas fields mature, water production increases and the flow conditions may convert from an oil-continuous to a water-continuous system. To understand the hydrate plugging mechanism of water-continuous hydrate systems, the flow characteristics of methane hydrate-water slurries was experimentally investigated by using a high pressure vertical loop. The slurry viscosity of different hydrate fractions was measured using an in-line viscometer. Accumulation, deposition and sloughing of the hydrate particles were investigated by video imaging and viscosity measurement. The plugging mech-anism in a water-continuous hydrate system was extensively analyzed and hydrate deposition and sloughing were observed. The density difference and agglom-eration of hydrate particles is considered as the major cause of hydrate accumulation and deposition, which subsequently instigates plugging in water-continuous systems.