Investigation on hydrates blockage and restart process mechanisms of CO2 hydrate slurry flow

Abstract

AbstractBeing an alternative environment‐friendly fluid for the refrigeration process, CO2 hydrate slurry is undesired to result in hydrate blocking in the system. A series of water‐based CO2 hydrate slurry experiments were conducted to investigate hydrate blockages in a high‐pressure flow loop. Blocking would occur soon after CO2 hydrate formation onset. Rapid restart process after the first blocking was found to have serious consequence by inducing a fast hydrate regrowth and an irreversible secondary blocking. The mechanisms of the first blocking and the secondary blocking after the restart process were proposed, based on the observed phenomena and the particle chord length distribution data recorded by focused beam reflectance measurement probe. The influences of the initial flow rate on the supercooling, the induction time, the restart time, and the required time for the secondary blocking after the restart process were analyzed. The understanding on the blocking and restart process mechanisms of CO2 hydrate slurry is important not only in the development of hydrate‐based refrigeration system but also in the field of flow assurance in the oil and gas pipeline or for other applications such as the replacement of methane by CO2 in the naturally occurring hydrate exploration.