Ageing assets pose challenges to oil & gas when operated past their design life. With the high level of oil & gas prices on the world market, buoyed by the lack of any viable alternative source to satiate growing energy demand, operators are seeking to maintain production from existing facilities for longer than their intended design periods. While they endeavour to do so, the risk to safety, reliability, and the environment need careful consideration.
DNV has various services tailored to this ever growing market. However, few docunents addressed the requirements of a fixed offshore asset comprehensively. Driven by the need to capture life extension requirements of all important facilities under one umbrella, DNV has now created a comprehensive methodology for life extension of fixed offshore units.
AGEING OFFSHORE TODAY
Ageing assets form a substantial world market, as more offshore assets – in all geographic areas – reach or surpasstheir design life-span. Life extension is a top priority. For example, hundreds of Fixed Offshore Platforms (FOUs) in the Middle East are approaching or have exceeded their design life. North Sea offshore production facilities, built in the ‘70s and ‘80s, had a design life of 25 years and are over 20 years old. The average age of Norway’s offshore installations is near 25 years, past the intended productive lifespan. Similar situations exist
in the U.S., Brazil, and in South East Asia.
Illustration of the life extension process
This project took ongoing life extension assessment techniques and created a comprehensive Remaining Life Assessment (RLA), unified across the various facilities and elements of offshore assets. The DNV Abu Dhabi office took the lead, coordinating, analyzing and compiling the methodology. The methodology is derived from DNV best practices and other relevance references from outside DNV. Subject matter experts contributed from DNV offices around the globe.
The report captures the methodology for the assessment of remaining life for the structure, pipeline, topside and wells of an ageing FOU. The methodology provides the basis for techno-economical assessments upon which decisions can now be made for the safe extension of FOUs beyond their original design life. The comprehensive RLA also analyzes the status of the installation, its associated facilities and the investment needed to ensure that the extension period is economically efficient.
The report proposes that at the start of a life extension assessment, a high level risk assessment of all major components be undertaken to identify critical and focus areas for further detailed assessment. Future cost analysis forms a part of evaluation. A Regulation Gap Analysis is then carried out to identify current regulatory gaps and assess the risks taken when operating with gaps. The critical equipment and facilities identified through as-is condition assessment may need detailed evaluation to arrive at actions and recommendations for life extension. For topside facilities of fixed offshore structures, the methodology suggests appropriate analysis for life extension of static equipment, rotating equipment, electrical and instrumentation components.
The structures of fixed offshore platforms are constantly exposed to a hostile environment. The approach detailed in the RLA identifies the structural asset reliability, integrity, vulnerability and risks associated with safe operations that need to be managed before it is approved for operating beyond its design life.
The methodology also addresses pipelines, addressing potential problems by using a variety of engineering methods to predict the remaining safe lifespan. These methods include both simple and complex fitness for purpose analyses as well as other care and maintenance elements.
Following the Macondo accident, a greater focus on safe drilling and well operations is present in the industry. Traditionally, well integrity management has been conducted independently from integrity management of other assets. Only in recent years have operators started to use systematic integrity management principles. The RLA developed by DNV presents a recommended approach to integrated well integrity management and risk based inspection. The methodology presented captures the practices that DNV has adopted to help global operators maintain production from existing facilities for longer periods, safely and efficiently.
Overall framework for an Asset Integrity Management System