A changing scene
Mature offshore fields, in the North Sea and elsewhere, are all operating against a background of:
- Falling production rates
- Increasing unit costs
- Infrastructure fast approaching, or already operating beyond, its design life
Until recently the response of the operating companies was a combination of divestment, decommissioning and dismantling. But over the last few years there have been significant changes in the industry:
- Changes of operating companies
- Higher, but volatile, oil prices
- Improvements in drilling and well technology
- Increased recovery rates
- Tie-in of smaller, previously marginal, fields to existing (ageing) infrastructure
The result is that the equipment installed on offshore installations may now be required to remain in service for anything up to 20 years beyond its original design life.
Consequence
One of the consequences is that stakeholders are increasingly looking for the following when considering the implications of extending the operating life of their assets:
- Continued licence to operate - technical justification for operating the equipment beyond its design life
- Confidence in continued safe, reliable and profitable operation
- Knowledge for investment decisions - future CAPEX and OPEX requirements for the asset. Typically $100m
- Quantified improvements to the bottom line - avoiding production losses and expenditure, from the improvements
- made
Meeting the challenge
ABB Engineering Services has been applying its structured asset life extension methodology to enable offshore operators to address these issues. The methodology ensures that the full range of factors affecting the integrity of the asset over its extended operational life are considered in a rigorous and structured process.
- Degradation mechanisms - corrosion, fatigue, creep etc.
- Obsolescence
- Changes in process fluids or conditions
- Workforce age and competency
- The quality of historical records
- Dependence on contractors
- Existing initiatives to improve asset reliability and integrity
- The regulatory framework and changes in legislation
A typical design life for topsides equipment is 25 years. Operating beyond design life does not necessarily mean that it is no longer fit for service and will automatically require replacement. ABB’s experience from conducting asset life extension studies is that, under the right circumstances, much of the topsides equipment can be operated for far longer. This is frequently against a requirement to cope with increasingly onerous operating conditions.
The deliverables of these studies provide:
- Equipment criticality ratings and approaches for the mitigation of risk
- The current status of the equipment versus the effective degradation mechanisms
- Identification of the actions necessary over the extended life cycle and the associated OPEX requirements
- The development of CAPEX profiles for the investment required to maintain asset integrity, reliability and uptime
- The capability of the equipment against the anticipated production profiles
Benefits generated
Typical findings for topsides equipment are that 75 to 80 % of the installed equipment can continue in service with the appropriate maintenance and inspection regimes. Circa 10% of the equipment requires replacement or major repair and a further 10% is likely to require minor repairs during the extended operating life. The benefits derived from these studies give a typical payback better than 10 to 20 times the cost of the study.
For more information on this article please contact: Andy Hollins, Principle Consultant, ABB -
andy.hollins@gb.abb.com