475500 CFD Simulations and Experiments in Multiphase Flow for Predicting Solid Particle Erosion: Challenges and Success Stories (Invited Talk)

Tuesday, November 15, 2016: 12:30 PM
Union Square 22 (Hilton San Francisco Union Square)
Siamack Shirazi, Erosion/Corrosion Research Center, University of Tulsa, Tulsa, OK

Solid particle erosion is a major problem in many industrial applications where solids are entrained in gas and/or liquid flows. For example, erosion of production equipment, well tubing and fittings is a major operating problem that costs the petroleum industry millions of dollars each year. Entrained sand particles in the oil/gas production fluid impinge on the inner surfaces of the pipes, fittings, and valves that result in solid particle erosion. Even in situations when sand control means are utilized such as gravel packing and sand screens, small sand particles can plug sand screens promoting higher flow velocities through other portions of sand screens causing failure of sand screens and allowing sand production. Erosion can cause severe damage to the piping and equipment wall, resulting in loss of equipment and production downtime.

Prediction of erosion in multiphase pipelines is a complex problem due to the lack of understanding of solid particle distribution in the liquid and gas phases and their corresponding velocities. The particle impact velocity is affected by the pipe geometry, carrying fluid properties and velocity, flow pattern, particle size and distribution in the flow. Among different multiphase flow patterns in horizontal and vertical flows, severe erosion damage can occur in annular and slug flows with high gas velocities and low liquid velocities. Although there is a lack of accurate mechanistic models to predict solid particle erosion, there is a need to develop engineering prediction models for multiphase flows.

It is well known that solid particle erosion rates is a strong function of the impacting velocity of particles and also the mass of impacting particles or the particle rate on a certain location. Predicting solid particle erosion in multiphase flow is a complex task due to existence of different flow patterns. The existence of different flow patterns and sand and liquid holdup in vertical and horizontal pipes means that a unique erosion model has to be developed for each flow regime if the model has to account for the number and velocity of impacting particles. In current efforts at the Erosion/Corrosion Research Center, local void fraction measurements by Wire Mesh Sensors (WMS) and Computational Fluid Dynamics (CFD) simulations of multiphase flows are employed to aid in predicting gas-liquid-sand velocities in multiphase flows. For the first time, CFD is used to compute erosion rates in multiphase flow. Local fluid velocities in multiphase flow are used to as a basis to determine representative particle impact velocities. Also based on data and simulations representing sand holdup in several flow regimes, the mass of impacting particles are estimated. Erosion experiments are also conducted on elbows in a 3-inch and 4-inch large scale multiphase flow loop with gas, liquid and sand flowing in vertical and horizontal test sections. Based on the experimental data and simulations for different flow regimes including slug, wet gas and annular flow a mechanistic model is being developed to predict solid particle erosion rates in multiphase flow.

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