Sand Erosion Mitigation for Offshore Pipeline and Riser – Erosion Prediction by Computational Fluid Dynamic CFD Analysis and Experimental Testing

Abstract

Late life production of oil & gas facilities are faced with significant challenge especially when sand is produced along with the production fluid. It can cause premature failure of the equipment, for example piping and pipeline. Mitigation by adding sand removal facility is limited by space, available load, and handling at satellite wellhead platform. It also introduced additional pressure drop which limit the production that already in low pressure. One of the measures to mitigate sand erosion issue for the offshore pipeline and riser is by flow assurance, to reduce the flow velocity so that the sand velocity will be less than the erosional velocity. This mitigation comes with drawback where reducing velocity will require bigger size pipeline, higher cost, and introduce higher liquid dropout along the pipeline which will create severe slugging issue in the pipeline. Next mitigation can be done by increasing bend radius along the pipeline, to reduce impact angle of the sand to the internal surface of the pipeline. Last mitigation will be increasing resistance of the material to the sand erosion. Combination of those methodology is required to achieve the most optimum solution to mitigate sand erosion. This paper present sand erosion mitigation on one of the existing pipeline replacement projects in PETRONAS by application of unbonded flexible pipe. Modeling of the of the erosion due to sand particle solution in the pipeline was done using computational fluid dynamic finite element analysis simulation. Experimental test with samples positioned at various orientation of the riser bend location were also investigated. Concerning the exceptional balance between results efficiency and simulation time, a grid sensitivity test has also been included. Various parameters were used to verify the sensitivity of the simulation including materials properties for various fluid composition data obtained from production forecast and fluid velocity as modeled in the pipeline steady state hydraulic analysis and transient flow assurance analysis. As result, the thickness of internal carcass is found sufficient to withstand the erosion threat generated by sand particles for the entire design life of the pipeline. The results obtained from finite element analysis and erosion experimental test were then correlated, and the comparison were illustrated in graph of velocity against erosion rate for each of sand concentration. The result of the modeling and experimental testing may improve prediction model of the sand erosion in the offshore pipeline especially for flexible pipeline and riser application.