Analysis Of The Attitude And Response Of The Underwater Structure During The Pendulous Process

Deep sea oil and gas exploitation relies more on subsea production system,and how to run the underwater structures to the subsea wellhead safely and accurately becomes one of the keys to exploit deep sea oil and gas.In this paper,the installation process of a new underwater structure installation method-Pendulous Installation Method(PIM)is studied.In order to solve the possible problems such as structural deviation,large angle flip,cable breakage and so on,a cable–structure coupling system is built by the multi-body dynamics analysis method.With the cable discrete using concentrated mass method,three-degree-of-freedom motion equations of the cable are established without considering the torsion of the cable.The authoritative submarine six-degree-of-freedom dynamical equations are used to establish the five-degree-of-freedom model of the underwater structure which does not consider the rotation of the structure about the vertical axis because of the special Anti-rotation mechanism.Then the motion equations and the mechanical equations of the structure is transformed into the boundary condition of the cable to form the nonlinear differential equations of the cable–structure coupling system.Then the data of installing a manifold in the Liwan area using PIM is chosen to simulate using the generalized ? integral method.The displacements and attitude angles of the structure under the given parameters are obtained by OrcaFlex.At last,the flow direction,the wet weight of the structure,the center of gravity offset and the floating center offset is analyzed to provide guidance on the selection of relevant parameters for the engineering practice in future.