Sand in producing wells can result in severe erosion even resulting in failure. This work investigates the effect of a variety of parameters such as diameter, flow velocity, particle size, and fluid properties on the severity of erosion for an elbow. The elbow is selected since it redirects the flow and experiences erosion from the impact of sand particles that do no follow the streamlines of the flow and impinge the pipe wall. A model previously developed for single-phase flow is presented and extended in this work for use with multiphase flow. Results for the maximum penetration rate in an elbow are examined for many parameters in both single-phase and multiphase flow. By assuming an allowable penetration rate, the erosion prediction model can also be used to determine the threshold velocity that would result in this penetration rate. The threshold erosional velocity curves are also generated for the multiphase flow cases.
The presence of sand in the produced fluid provides many challenges for oil and gas production and sand management has become increasingly important as high rate wells with sand become more prominent. One of the primary concerns created by the presence of sand is erosion. The sand impinges fittings and tubing resulting in loss of the wall material. The erosion damage can be significant resulting in failure in a relatively short amount of time. Failures provide a potential safety risk for personnel as well as equipment. Oil and gas producers need to be able to predict the severity of erosion so that the service life of fittings susceptible to erosion can be determined. If the prediction tool has the capability of accounting for parameters such as production rate or flow velocity, producers can also determine the highest production capacity that keeps the erosion damage within tolerable limits, maximizing the economic potential of the well.
Erosion is complex and depends on a multitude of factors such as the fluid and sand properties, production rate of produced fluid and sand, pipe size, and sand size. Therefore, developing predictive tools for erosion poses a difficult task. Another factor that affects the severity of erosion is the type of geometry. Most of the work that has been done on the development of erosion prediction models has been for elbows and bends. This is a result of two primary factors. First, the elbow is a relatively simple geometry, and second, the elbow experiences a significant amount of erosion.
