Effect of particle size on erosion measurements and predictions in annular flow for an elbow

Abstract

Sand production is a flow assurance challenge in oil and gas condensate wells. Solid particles entrained in multiphase during production can severely affect the integrity of fluid transportation structures such as pipelines, elbows, and reducers. Traditionally, sand management techniques such as sand screens and gravel packs are used to control sand. However, 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 promote erosion of the sand screen openings allowing larger particles to pass through which in turn cause more erosion. Furthermore, these small particles are susceptible to highly turbulent regions of flow and can cause severe erosion in these regions. Hence, it is critically important to understand the erosion caused by small particles. This study investigates the effect of small particles 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. Experiments are conducted in vertical upward annular flow for different particle sizes as well as different superficial gas and superficial liquid velocities for pipe sizes of 3-inch (76.2 mm). Flow visualization and paint-removal studies are performed to visualize the flow and paint-removal pattern. Erosion patterns are measured with multiple sensors attached to the outer walls of elbows in multiphase flows. Elbow wall thickness losses are measured using state-of-the-art ultrasonic measurement techniques, and the effects of particle size on erosion ratio and its distribution in pipe bends are discussed. Erosion patterns are also compared with Computational Fluid Dynamics (CFD) simulations of multiphase flows using the VOF Model. Current CFD results generally over-predict erosion compared to experimental data.