The Effects of Particle Size on Solid Particle Erosion of Elbows in Low Liquid and Annular Multiphase Flows

Abstract During production of oil and gas, sand is produced as an unwanted by-product. Sand particles of many sizes carried by the multiphase flow can severely affect the integrity of fluid transportation structure such as pipelines, elbows, reducers and other pipe fittings. Sand production is managed via sand screens and gravel packs. These methods are successful in handling relatively larger sand particles. However, fine particles (< 100-micron size) can pass through most of these controls whcih can block the openings of sand screens which in turn causes higher velocities in other portions of the sand screen. Because of these higher velocities beyond the intended design velocities, the other portions of the sand screen become eroded, lose their effectiveness, and let larger particles pass through them. Furthermore, these small size particles cannot be detected with traditional acoustic monitoring techniques. Moreover, these small particles are highly susceptible to be entertained in high turbulent regions of flow and can cause severe erosion in those regions. Hence, it is critically important to understand erosion caused by small particles along with larger particles. This paper describes the effect of particle size on erosion. Small particle erosion is more severe in gas than liquids because in liquid there is a large momentum exchange with particles. The experimental setup consists of two elbows in series in a flow loop for horizontal and vertical flows.Paint-removal and erosion experiments are conducted in annular flow for different particle sizes as well as different superficial gas and liquid velocities for a 4-inch pipe. The effects of particle size on erosion are discussed with the validated CFD model and flow visualization experiments.