(494h) Flow Properties of Gas Hydrate Slurry in Oil-Dominated Transportation Systems

As oil & gas industry develops into deep water, gas hydrate has been one of the major hazards to the deep sea flow assurance. Hydrate risk management strategy is a novel method for hydrate control, in which hydrate is allowed to form and the petroleum product is transported in the form of hydrate slurry. In this work, hydrate slurry flow properties in w/o emulsion systems were studied using a high pressure flow loop. The w/o emulsion was formed by deionized water and diesel oil in three different water cut (10%, 20% and 30%). Civil natural gas was used as the hydrate former and 1% AA was also used to avoid the blockage after hydrate formation. For each water cut condition, hydrate slurry flow experiments were carried out with four different velocities (0.39m/s, 0.58m/s, 0.97m/s and 1.29m/s). It was found that the flow friction factor increased obviously after hydrate formation, and would keep increasing with the increasing volume fraction of hydrates formed. The increase degree of the friction factor decreased with the increasing flow velocity and increased with the increasing water cut. But when the velocity was larger than 0.97m/s, the increase degree of the friction factor would no longer change with the velocity. Then, a model was proposed to estimate the hydrate-caused friction factor increase, which could well predict the flow fraction factor of hydrate slurry flow. In addition, based on the force analysis of the suspended hydrate particles, the stable suspension region of hydrate particles in different flow velocities were calculated. It was found that there was a critical suspension height in the hydrate slurry flow pipeline. If the hydrate particles suspended above the critical suspension height, the hydrate-caused friction factor would be small and would not change with the flow velocity; while if the hydrate particles suspended under the critical suspension height, the hydrate-caused friction factor would be large and would decrease obviously with the increasing flow velocity.