A COMPREHENSIVE PARAMETRIC STUDY OF STATIC BEHAVIOR OF TOP TENSIONED NEAR-VERTICAL RISERS

A near-vertical marine riser is a cylindrical pipe of an offshore platform that provides the connection between the wellhead on the seabed and the facilities on the platform to transmit the fluids and the equipment. A near-vertical riser is usually called a top tensioned riser. It involves a tensioning system to maintain its angles at the top and the bottom of the riser. This paper includes a parametric study on the static behavior of top tensioned risers through both the second-order central difference method that solves the nonlinear fourth-order differential equation in the MATLAB software and through the powerful finite element software, OrcaFlex. The parametric study includes the top tension, bending stiffness, outer diameter, wall thickness, and floater drift parameters. The study shows that increasing the wall thickness and outer diameter increases the lateral deflection and bending moment. Increasing the lateral platform drift (provided that the top tension ratio should remain constant) will intensify the bending moment slightly, although the curvature will remain constant. Increasing the top tension will diminish the lateral deflection and the bending moment along the riser length. However, the bending stiffness parameter variation does not affect the static analysis results as much as other parameters.