A CFD study on the Effects of Sand Particle Size on Erosion of an Elbow

During production operations from oil and gas condensate wells, sand particles also travel with the raw petroleum products. These sand particles impact the walls of transportation infrastructure and erode the wall thickness. This continuous degradation of wall thickness can result in leakages which has severe implications for production and safety. These sand particles can be of various sizes such as 300, 75, and 25 microns. Most of the studies on this phenomenon of solid-particle erosion focus on bigger particles such as 300-microns. Similarly, sand management techniques such as sand screens and gravel packs are used to control sand are specifically designed for bigger particles. However, recently the aging reservoirs are shedding small particles. These small particles can pass through these controls. Furthermore, small particles can block a portion of the sand screen, causing high velocities in other sections which can cause erosion of the sand screen openings allowing larger particles to pass through which in turn cause more erosion. Furthermore, these small particles are highly susceptible to turbulent regions of flow and can cause severe erosion in these regions. Hence, it is critically important to understand the effect of particle size on erosion behavior such as the location of maximum erosion, particle trajectories followed by various sized particles, and locations of maximum erosion. This study investigates the effect of particle size on erosion. Small particle erosion is more severe in gas-dominated multiphase flows such as annular and mist flows than liquid-dominated bubbly and slug flows. A 90-degree standard elbow is used in the analysis because of its high erosion vulnerability and its importance in pipeline applications. This is because the flow changes direction in this kind of geometry which has complex implications for erosion. Furthermore, the effects of particle size on erosion ratio and its distribution in pipe bends are discussed. The CFD results of larger particles agree better with experimental data than for smaller particles utilizing existing erosion models.