Particle-transport mechanism in liquid/liquid/solid multiphase pipeline flow of high-viscosity oil/water/sand

In this study, an investigation of sand transport in heavy-oil/water multiphase flow is performed. The study is conducted in three multiphase-flow pipeline-test facilities with internal diameters (IDs) of 1, 1, and 3 in. The pipeline orientations relative to the horizontal in the facilities are 0, þ30, and 0^o, respectively. Oil viscosity of 3.5 and 10.0 Pa.s with sand volume fractions from 0.010 to 0.100 vol% were used in the study. The effects of oil viscosity, upward inclination, sand volume fraction, pipe ID, and water cut on the sand-transport mechanism in pipelines are investigated. In the horizontal test section, flow patterns—namely, dispersed flow (DF), plug flow (PF), plug flow with moving sand bed (PFM), and plug flow with stationary sand bed (PFS)—were identified through flow visualization. In addition to the aforementioned, two flow patterns—stratified wavy flow with moving sand bed (SWM) and stratified wavy flow with dunes (SWD)—were observed in the inclined pipeline orientation. The pressure gradient measured decreased with a decrease in water cut until a minimum value was reached. Beyond the minimum pressure gradient, further reduction in water cut led to an increase in pressure gradient. The sand minimum transport condition (MTC) in the oil/water/sand test was largely the same for the 1-in. 30^o upward inclined and the 1-in. horizontal test section. In contrast, that of the 3-in. horizontal test section was considerably higher. An improved MTC predictive correlation is proposed for multiphase heavy-oil/water/sand flow. The proposed correlation outperforms the existing models when tested on the heavy-oil/water/sand data set.