The Latest Developments In the Design And Simulation of Deepwater Subsea Oil And Gas Pipelines Using FEA

This paper gives an overview of the latest developments in how advanced finite element analysis (FEA) tools can be used for the design and simulation of subsea pipelines and components. Through the use of these tools, it allows designs to be undertaken for complex scenarios that were not previously possible, and confronts key technical design challenges such as pipe-in-pipe (PIP) in deepwater and high-temperature situations. This paper is split into three main parts, and covers the use of cutting-edge FEA tools for the design and simulation of pipelines and components. The first part looks at the ‘global’ analysis of pipelines using a highly non-linear finite element (FE) program, which has been developed called ‘Simulator, and uses ABAQUS as the finite element engine. These tools can be used to undertake complex design cases such as lateral buckling, upheaval buckling, reeling and installation analysis, single pipe and pipe-in-pipe response, pipe-soil interaction, fatigue, expansion-span analysis and thermal buckle management. The second part of the paper demonstrates how FEA can be used to undertake ‘local’ modeling of pipelines and components. A local full-size PIP FE model is used to verify the global PIP FE model at a local level. Also solid modeling of complex subsea components such as bulkheads, flanges, girth welds and clamps are described. The third part of the paper looks at an integrated approach to route selection, using three-dimensional (3D) software and stress analysis, to reduce pipeline length and minimize intervention. Using the above-mentioned tools, project examples are then given where the FEA tools are used to address deepwater and high-temperature issues. The combination of these analysis tools allows solving some of the most complex engineering problems presently faced in the industry, and in some cases has allowed significant cost savings to be achieved in the engineering. INTRODUCTION — WHY USE ADVANCED FINITE ELEMENT ANALYSIS? The industrialized nations of the world continue to consume the oil and gas resources of the planet, and this is set to continue into the future. As a result, future demand will require exploiting new opportunities for oil and gas from more difficult and harsher locations, such as deepwater, and under more extreme conditions, such as high temperature. These complex scenarios present real technical challenges in terms of the design. Technical Challenges Technology gaps exist and the inability to bridge those gaps due to technology either being unavailable or just too expensive to implement, has put some projects on-hold for many years. A number of engineering challenges, or technology gaps, have been identified that have a significant impact on the design of oil and gas pipelines, and subsea equipment (Jukes, 2009; Jukes, Wang, and Duron, 2008; Jukes, 2007). The main technical challenges that exist are identified as: deep water, highpressure/high-temperature (HP/HT), thermal performance, inner pipe locked in compressive loads and ultimate load capacity for pipe-in-pipe (PIP) systems, design code limitations, ultra-deep water and installation, soft soils, flow assurance, and thermal buckle management. Flowline designs are presently being considered, for a major operator, in the Gulf of Mexico (GoM) for water depths down to 3,000 meters (10,000 ft), pressures in the order of 700 bar (10,000 psi) or more, and temperatures up to 177 °C (350 °F). These types of onerous conditions of temperature, water-depth and pressure can present real design challenges in the choice of materials and design methodology (Jukes and Harrison, 2006). 70 Proceedings of the Third (2009) International Deep-Ocean Technology Symposium Beijing, China, June 28-July 1, 2009 Copyright © 2009 by The International Society of Offshore and Polar Engineers (ISOPE) ISBN 978-1-880653-73-9