1 INTRODUCTION

Particle transportation is a common flow assurance problem occurring in oil and gas pipelines. When production takes place in oil and gas wells, oil, gas, water and impurities are produced and transported through the pipeline. Common impurities produced in oil and gas wells are sand particles, hydrates and wax. Depending on the flow rate, fluid condition, pipe size and sand properties, sand particles can either move along as suspended particles in the flow (dispersed), scouring along the pipe wall, as a bed of particles (dunes) or remain stationary. At high flow rates of oil and gas, particles become suspended and travel at high velocity and upon collision with the pipe wall lead to erosion of the pipe wall material. At low flow rates of oil and gas, the particles settle down to the bottom of the pipe, and the particles may or may not move. This can lead to other flow assurance problems in the pipeline such as blockage, under deposit corrosion and increased pressure drop. The properties of fluid, solid and pipe affect the particle transportation in the pipeline. The fluid properties includes density, viscosity, and composition of fluid; particle properties includes size, shape, concentration; pipe geometry properties include diameter, shape, and roughness of pipe.

Because of the importance of this topic, many investigators have developed models for predicting critical deposition velocities. For example, Figure 1 shows a prediction of particle transport velocity using a model proposed by Najmi et al. (2015) and comparison to experimental data collected in a 0.1016 m (4 inch) pipe at the Tulsa University Sand management Projects (TUSMP). The curves shown are velocities needed to transport particles for a particle volume concentration of 0.1%. However, in many applications the concentration of particles is very low and this model needs to be extended to situations involving very low concentrations.

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