Current flow loop equipment and research in hydrate-associated flow assurance

Abstract Flow assurance has been considered as a major technical problem in offshore oil and gas facilities, where hydrate blockages are frequently encountered. Intensive efforts are thus being made in laboratory to understand the behavior of gas hydrate generation, aggregation and deposition. Albeit apparatus like high pressure autoclave and rocking cell are developed, limitations still remain in terms of mimicking the fluid flow in the pipelines. Consequently, flow loops enable a successive flow of the fluids inside, better reproducing the hydrate formation and slurry flow process. At present, dozens of flow loops have been established around the world. In this review, 18 widely used of them are comprehensively introduced. According to the vintage of construction, these devices are divided into early flow loops (1995–2005), intermediate flow loops (2005–2015) and new flow loops (2015–2019). Their structural parameters and special features were compared in detail. Five major topics carried out using these devices are also discussed, involving hydrate formation and growth in pipeline, hydrate particle aggregation and deposition, hydrate slurry flow characteristics, mechanism of hydrate plugging, hydrate plugging prevention and removal. The results could provide reference for the future construction of new flow loops with a broader application. Suggestions are also put forward on the potential studies to be carried out with the flow loop device. The macro phenomenon and micro mechanism should be connected, and further data analysis and simulation methods are still required to reveal the interacting and coupling influence factors of hydrate blockage behavior.