Compared with the available commercial software such as OrcaFlex, the calculation of the present model has the advantage of high stability and being time-saving. The governing equation system is derived and the analytical approximate solution is obtained by means of HAM. The bending stiffness and large deformation of the part suspended in water are taken into consideration.
The structural model presented in this paper is a simple and practical method to obtain the static configuration and the mechanical load parameters for SCR transfer process. Thus, an analytical solution for SCR installation can substantially reduce design time and provide a quick evaluation of actual installation setting. Therefore, a simple and effective SCR installation model is still important for engineers to understand the nature and relevance of the complex phenomena during installation. But it might be time-consuming depending on the performance of computer. Nowadays, finite element software such as OrcaFlex is commonly used to solve optimal installation path problem. used two-dimensional Navier-Bernoulli beam to analyze pipeline laying process, and an updated Lagrangian formulation for the nonlinear analysis was obtained. Lenci and Callegari investigated some analytical models to analyze the J-lay method, but the solution is not easy to obtain because the equations are highly nonlinear. established a nonlinear mechanical model to analyze the pipeline lifting process and applied a shooting method in solving the moving boundary problem. used line integration technique to analyze the tensions of A&R wire while considering the movement of installation vessel. Guarracino and Mallardo developed the expansions to analyze the S-lay method. Dixon and Rultledge applied Plunkett’s expansions in analyzing J-lay method. The nonlinear large deformation beam theory is more appropriate for simulating the riser near touchdown point (TDP) considering the large-angle deformation. The catenary theory is a simple model for evaluating the tension and curvature of SCR, but it cannot simulate the rapid change of the inclination angle because it ignores the bending stiffness.
A large number of papers have been published on this issue. The shape of SCR will be affected by the route of pull-head during installation controlled by both the A&R and the pull-in wire, and the maximum stresses to be encountered during the transfer process must be obtained before installation. The transfer process is divided into prelay and postlay, depending on whether the offshore platform is on site.
The transfer process is usually carried out by J-lay vessel, since the S-lay vessel cannot install SCR independently. During SCR installation as shown in Figure 1, the pull-head is transferred from installation vessel to platform by Abandon & Recovery (A&R) wire from installation vessel and pull-in wire from the platform.
In deepwater exploration, SCRs are widely used as a cost-effective riser system which is connecting offshore platforms and subsea production systems. In response to increasing global demand of energy from fossil fuels and the replacement of depleting oil and gas reserves in most matured fields in the world, operating companies in the oil industry are expanding their exploration and production operations into deepwater. Engineers may efficiently optimize the installation path by the application of this technique. Based on this analytical solution, a program within the framework of MATLAB was developed to predict the two-dimensional riser behavior during installation, and a sensitivity analysis for different values of the control variables was carried out. Since the SCR installation path calculation through numerical simulation software is usually time-consuming, this paper has established a mechanical model for SCR installation by making use of homotopy analysis method (HAM) to simplify its analytical solution, and dimensional analysis was considered in making initial guess solution. During SCR J-lay installation, the movement of pull-head must be carefully controlled to ensure riser safety. Steel catenary riser (SCR) is a cost-effective riser system that is widely used in deepwater offshore oilfields development.