Offshore Oil and Gas Installation - Aging and Life Extension

Abstract

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 146225, ’Aging and Life Extension of Offshore Oil and Gas Installations,’ by Iain Wright, ABB Engineering Services, prepared for the 2011 SPE Offshore Europe Oil and Gas Conference and Exhibition, Aberdeen, 6-8 September. The paper has not been peer reviewed. More than half of the offshore oil and gas installations in the UK Sector of the North Sea have been operating for at least 20 years. Most assets are approaching or operating beyond their original design intent. With the rise in oil and gas prices and advances in technology, there is an increasing requirement to extend the operational life of these assets. Safety-case regulations were modified to include a technical justification for extended operation, and the UK Health & Safety Executive (HSE) launched Key Programme 4 (KP4) to ensure that all duty holders have suitable management systems in place to address aging-related issues adequately. Introduction Coupled with the age is that most installations have encountered considerable changes in the composition of the well fluids over the life of the field and that there is an increasing trend for additional subsea tiebacks. All of these issues have raised concerns regarding the integrity and fitness for purpose of the structures and equipment for this extended life. This study aimed to answer key questions relating to aging and life extension. Aging and Life Extension According to HSE Research Report RR509—The Plant Ageing Guide, “Ageing is not about how old the equipment is. It’s about what is known about its condition, and how that’s changing over time.” This definition is illustrated in Fig. 1. During the initial operation phase, design faults, installation issues, commissioning issues, or early-life operating faults are realized. Once equipment is in the mature stage, it generally is operating well within design limits, routine inspection and maintenance are being undertaken, and, in general, there is slow degradation. During the aging stage, the design limits for the equipment are approached, process changes usually have taken place, frequent repairs are required, and the overall degradation rate increases. In the end-of-life stage, the safe operating limits for the equipment are approaching, advanced inspection techniques are required at closer intervals to determine fitness for purpose, major repairs are required, and there is accelerating deterioration. The key to longer-term reliability and safety is to establish effective management systems early on to prolong the mature stage, because starting at later stages requires considerably more effort and cost.