Subsea Well Life Extension Fatigue Challenges
EVENT: SPE Bergen
1 Apr 2015
The growth in oil price and improvement in techniques for recovery of oil is resulting in an increasing need to keep subsea wells that have exceeded that initial design lives in operation. Life extension will require further drilling on the wells, the feasibility of which must be assessed in terms of the fatigue damage accumulation in the wellhead system. Consideration of fatigue resistance in the design of older wells was limited, if conducted at all, which has resulted in design features that form fatigue hotspots. Such features, coupled with the additional loading applied in further operations can lead to severe challenges in demonstrating fitness-for-purpose in terms of fatigue response.
Calculation of fatigue damage from both previous and future operations is conducted to demonstrate acceptable response. This analysis typically involves a number of assuptions that err on the side of conservatism. However, the severity of loading is such that steps must be taken to minimise these conservatisms where reasonably possible in order to meet faigue life targets. This in itself may not be enough, and the use of in-service monitoring and even component fatigue testing may be needed to meet the required objectives. This paper gives an overview of the design challenges that are faced in extending the service life of older wells, the steps that can be taken to improve calculated fatigue lives and how further steps such as in-service monitoring may be used to demonstrate fitness-for-pupose.
Authors
Alex Rimmer
Director, UK
About
Alex joined 2H Offshore in 2004 and has been a UK Director since 2011, based in 2H’s London Office. He is jointly responsible for 2H’s European offices and engineering activities across the EMEA regions.
Alex is a Chartered Engineer with the IMechE and holds a first-class Master of Engineering degree from the University of Bath. He has over 20 years of project execution and management experience developed at 2H and in previous roles.
He is a recognised subject matter expert in dynamic subsea system analysis and engineering and provides technical oversight and consultancy to a broad range of deep and shallow water energy projects. He specialises in all types of drilling, completion and production riser systems, as well as platform well and subsea well systems. For the past 5 years, he has primarily been driving forward 2H UK's floating wind (coupled analysis, power cables, moorings and anchor piles) and CCUS well activities, but continues to support the projects in oil and gas as well.
He has been involved in many challenging and innovative offshore subsea and renewable developments. His energy sector highlights include BP’s Block 31 PSVM and Total’s Kaombo hybrid riser detailed designs, Total’s West of Shetland UK subsea development and many of Aker BP’s well platforms in Norway. Renewable energy highlights include support to industry initiatives with ORE Catapult on floating wind HV power cables, and several pioneering wave energy and floating wind platforms and developments.
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Phil Ward
Principal Engineer
About
Phil is a principal engineer in 2H’s Houston office. He holds a master’s degree in Engineering from Cambridge University and has 14 years’ experience in the oil and gas industry with various types of pipeline and riser designs, subsea structural monitoring systems, and late-life assessment techniques. Phil started his career with 2H in Aberdeen, and held the director position there before relocating to 2H Houston in 2019 with the goal of cross-populating experience with shallow and deep water systems. He has held numerous project management and technical leadership roles on a variety of projects from concept through to detailed design, including subsea wellhead fatigue mitigations, platform well design optimisation and thick-wall SCRs. Phil is a Chartered Engineer and Member of the Institute of Mechanical Engineers.
