Investigating the effectiveness of anti-agglomerants in gas hydrates and ice formation

The disruption by gas hydrates in the multiphase oil/gas production and transportation system is undesirable. One strategy for hydrate management is the injection of anti-agglomerants (AAs), allowing to form flowable hydrate slurries. For long tie-backs for gas and/or condensate under cold environments (the North Sea and deep offshore), combined with a Joule-Thomson cooling, the temperature can often decrease below 0 degrees C. In such cases, hydrate slurries first formed with AAs enter into the ice region. Thus, the impact of AAs on ice/hydrates formation needs to be identified for safe and sustainable operation. Transportability of hydrate slurries inside the ice region and AAs efficiency on hydrate/ice slurries formation has not been previously studied. We investigated the performance of AAs under the flow of water and oil on ice formation, and gas hydrates formation followed by ice formation using the rock-flow cell, which enables direct visual observation to see when, where, and how those solids form. Without AAs, solid hydrates and/or ice bed stick to the bottom of the pipe, thus reducing the flowability. While the poor-performing AA does not largely change how hydrates and ice form, the good-performing AA can disperse hydrate beds into flowable slurries, ensuring flowability. Ice chunks may still form, but they flow well along with hydrate slurries in the conditions tested. This ice/hydrates co-existence and co-formation are of great interest in certain field conditions, and thus the effect of AAs has to be re-evaluated to optimize their use for successful risk management in oil/gas production systems.