The Study of Gas Hydrate Formation and Particle Transportability Using A High Pressure Flowloop

Abstract

As oil and gas industry strive for better gas hydrate management methods, there is the need for better understanding of hydrate formation and plugging tendency in a multiphase flow. In this work, an industrial-scale high pressure flowloop was used to investigate gas hydrate formation and hydrate slurry conditions at different flow conditions; fully dispersed and partially dispersed systems. It has been shown that hydrate formation in partially dispersed system can be more problematic as compared to fully dispersed system. For hydrate formation in partially dispersed system, it was observed that there is rapid hydrate growth and rapid increase in pressure drop upon hydrate formation. This is in-contrast to fully dispersed system in which there is gradual increase in the pressure drop of the system. Further, for partially dispersed system, studies have shown that there is hydrate film growth at the pipe wall. This film growth increases the probability of hydrate particle agglomeration and bedding phenomenon, which that lead to flowline plugging. As there is different hydrate formation and plugging mechanism for fully and partially dispersed system, it is thus necessary to investigate and compare systematically the mechanism for both systems. In this project, all experiments were specifically designed to mimic the flow systems that can be found in actual oil and gas pipelines (full and partial dispersion) and understand the transportability of hydrate particles in both systems. Two variables were investigated in this work; amount of water (water cut, WC) and pump speed (fluid mixture velocity). Three different water cuts were investigated; 30, 50 and 90 vol.% water cut. Similarly, three different pump speeds were investigated; 0.91, 1.89, 2.99 m/s. The results from these meausrements were analyzed in terms of relative pressure drop (?Prel) and hydrate volume fraction (fhyd). It was observed that for all water cuts investigated in this work, the ?Prel decreases with increasing pump speed, at a similar hydrate volume fraction. Flowloop plugging occurred for tests with 50 vol.% water cut and pump speeds lower than 1.89 m/s, and for tests with 90 vol.% water cut at a pump speed of 0.91 m/s. Additionally, in all 90 vol.% water cut tests, emulsion breaking where the two phases (oil and aqueous water) separated was observed upon hydrate formation.