Solids Transport in Multiphase Flows—Application to High-Viscosity Systems

Solids transport in multiphase systems falls under the umbrella of “flow assurance.” Unlike issues such as waxes and hydrates, solids transport has received relatively little attention to date. This is especially true for solids transport in high-viscosity fluids such as Venezuelan crude, where viscosities around the 300–400-cP mark are commonly encountered. This paper describes some experiments performed on the BP Amoco 6-in. multiphase flow test facility located at Sunbury. These looked at the transport of field representative sand through a pipeline dip. Several fluids were selected for these experiments to examine the influence of liquid viscosity on the results. These were water, oil, and two different carboxymethylcellulose solutions (150 and 300 cP). These experiments showed that, in slug flow, water and low-viscosity oil were able to transport the sand uphill, whereas neither high-viscosity solution was able to transport the solids. This feature was examined in comparison to the model for solids transport in near-horizontal pipes discussed in this paper. Three-phase flow experiments (water-oil-air) were also performed to investigate the effect of oil or water prewetting of the solids on solids transport. If prewetted by water, the sand could not be moved by oil slugs. Once water was added to the system, the sand became increasingly mobile.