Influences of Pipelay Parameters on Dynamic Behavior of Deepwater J-Lay System

Abstract

J-lay is currently the most appropriate technique for pipeline installations in deep and ultradeep waters. Pipelay parameters can significantly influence the dynamic behavior of deepwater J-lay systems. This study proposed a fully coupled finite-element model (FEM) for deepwater J-lay systems using the software OrcaFlex to predict the dynamic responses of the pipeline and the seabed caused primarily by hydrodynamic loads and vessel motions. Meanwhile, an advanced hysteretic soil model and a bilinear Coulomb friction model were employed to simulate the vertical and lateral pipe-seabed interactions, respectively. The influences of some important pipelay parameters, such as the water depth, departure angle, submerged weight and outer diameter of the pipe, J-lay tower location on the dynamic behavior of the whole pipeline, and the seabed in the touchdown zone (TDZ), were estimated quantitatively. Then, the dynamic laying effects of the pipelines on aspects of the effective tension, bending moment, equivalent stress and strain, pipeline embedment, and seabed resistance were systematically identified. The significant findings provide a comparatively good work basis for the pipelay parameter optimization design of deepwater J-lay systems.