Real-Time Finite Element Analysis of a Remotely Operated Pipeline Repair System

Abstract

Remotely operated vehicle (ROV) pilots are frequently trained to operate in increasingly complex subsea environments using ROV simulators. These computer simulators de-risk important subsea operations by increasing ROV pilots’ skill levels in performing tasks under challenging environmental and operational constraints. ROV pilot-training simulation scenarios typically involve a variety of subsea equipment, such as trees, flow lines, pipeline end terminations (PLETs), etc. However, many critical ROV tasks, such as pipeline repair or riser installation, involve flexible structures. The following paper investigates a method for accurately simulating pipelines and flexibles within an ROV pilot-training simulator. The goal of the technology development is to enable engineers and marine operators to assess the risks associated with certain tasks, such as pipeline repair or flexible hook-up, in real-time using ROV simulation technology. In particular, the challenge that this paper will address is how to determine the stresses in a subsea pipeline using a lumped mass finite-element cable model within a multi-body simulation framework. Repair of subsea pipelines is a complex multi-step process typically carried out by ROVs. During pipeline repair, a pipeline repair system (PRS) is lowered to the seabed. The PRS must lift the pipeline off the seabed and the damaged section of pipeline must then be cut and removed, and a new section of pipeline put in place. During the lifting, cutting and installation phases it is important that the pipeline is not overstressed and the equipment used in the repair operation is not overloaded. In addition, there are a wide array of operational variables, procedures and decisions that must be evaluated. Towards this end, an ROV simulation facility capable of assessing stresses and operations in real-time was constructed using the finite element simulation software package ProteusDS in conjunction with GRI Simulations Inc.’s VROV simulator. The system was designed to evaluate the impact of different combinations of operating parameters and is intended to be useful for system design and analysis. The system would be of immense utility in rapid response to a real-world incident where the system may be called into action. The following paper reviews the simulation framework, the models employed, the results of model verification, and discusses the challenges of the project.