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In general, Lay and Tow methods are the two most common methods of offshore pipeline installation. In the shallow waters, considering the restrictions of Lay barge, Tow method is usually more appropriate. In this method, pipestring is fabricated on-shore and then it is launched into water. Then, according to environmental conditions and restrictions, the pipeline is towed to the installation site. In the present study, the evaluation of stress and deformation along pipeline during transportation and installation in shallow water has been presented. All analyses have been carried out using Orcaflex software. A parametric study has been carried out on the effect of environmental loading (wave and currents) and other parameter such as tugboat pull capacity and reserve buoyancy rate. Also lateral and vertical displacements and stress on pipeline for different conditions including static, transportation and laydown conditions have been investigated. For modeling properties of the pipeline, an existing pipeline in the Persian Gulf is considered. Due to the pipeline floating condition, the effect of the tug motions due to wave is ignored. The results are shown that lateral deflection of the pipeline due to wave spectrum is less than monochromatic waves with a maximum height of the wave spectrum. Also, by increasing tug speed, lateral curvature is closer to the end of the pipeline and increases the bending stress due to lateral curvature.

Keywords: Offshore Pipeline, Surface Tow Method, Regular and Irregular Wave Analysis

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