Pigs are widely used in pipelines and help with meeting operation goals such as keeping the continuous operation and providing the desired throughput and other applications including inspection, cleaning, and also pipeline filling and dewatering. The present study examines leakage and mixing of oil and water during dewatering operations for oil transmission pipelines. When the pig passes through bends and fittings, the sealing between the pipe and the pig becomes less effective and leakage occurs from oil which is pushing the PIG into the water and from water into the production. Therefore, the leaking fluids across the pig cause significant amounts of oil mixing with water ahead of the pig causing environmental issues and a significant amount of waste product downstream (in front) of the moving PIG. On the other hand, water droplets behind the pig can settle causing droplet deposition and corrosion risk. This study aims at modeling the leaked fluids across a pig and the dispersion of the multiphase flow using Computational Fluid Dynamics (CFD). Dynamic models are employed to examine the development of oil-water dispersion. Different scenarios such as the motion of the PIG in a straight pipe with 1-inch (25.4 mm) ID or its passage over a Tee junction is investigated. Through CFD simulations, multiphase flow characteristics such as the water distribution around the pig are examined. Afterward, based on the water concentration, the phase-wetting condition would be identified which assists in pipeline corrosion risk assessment.

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