Benchmarking reliability

The capability to benchmark the reliability of safety-critical well barrier components against a global component test database will enable oil and gas operators to optimize asset performance, Ged Lunt says.

Optimizing asset performance remains a continuous challenge for oil and gas operators. A key element in achieving this is selecting well equipment with reliable performance. However, making the correct selection is far from simple; different equipment models may be more suited to certain operating conditions. When conditions are very challenging, well designs may need to be adjusted to allow for lower achievable reliability of particular equipment to maintain an acceptably low overall level of well failure risk. A lot of considerations lie behind the selection of well designs and the selection of replacement components during well workovers.

The performance of installed well components must be totally predictable. Should a problem arise at any given point in time, operators must be confident that they know how their well barrier components will respond. For example, if they shut a subsurface safety valve (SSSV), then they know with certainty that it’s going to close and contain the well fluids in the specified time.

Getting accurate reliability figures for well barrier components requires access to a statistically significant database. While the industry recognizes this need, a key challenge has been the reticence of operators to make data such as component reliability and failure rates available externally.

In addition to concerns over data confidentiality, efforts to build such a database have tended to be limited to single regions such as the North Sea, or focused strongly on specific components such as the SSSV. Previous systems have also been badly structured and suffered from poor quality of data or difficulty of use or access.

Better insight, better decisions

Wood Group Intetech launched a global database of well performance data called iQRA. This online quantitative reliability analysis tool provides operators with access to global well and oilfield component performance information, so operators can identify the highest performing well components, benchmark reliability figures, and extract statistical and mean-time-to failure (MTTF) data to support cost-saving decisions.

Most operators accept that certain well barrier component failures are inevitable and operational constraints may mean that they cannot be repaired immediately. It can be necessary for wells with individual components not in full working order to continue to operate, provided risk assessment indicates the risk level is acceptable. Of course, some types of failure call for the well to be shut-in and repaired immediately, but for the majority of non-critical failures, repairs are scheduled to take place within a designated timeframe, or when the opportunity arises.

Testing can actually reduce the lifetime of the equipment – especially an active component that is opened and shut, each cycle causing some amount of wear and fatigue.

Given that it is necessary to close valves in order to test the leak rate across them, using risk-based analysis to determine that testing can be safely performed less frequently, should extend the lifetime of valves, as well as reducing operating costs.

Access to this kind of reliability information makes it possible for operators to identify where they have low reliability equipment or potentially a faulty component, and pre-empt potential failures on other wells by taking the opportunity to replace equipment if another well intervention is taking place.

Meeting user needs

The ability to benchmark company performance against the global database is attractive for operators, as is the functionality to carry out reliability and MTTF evaluations and the provision of robust and risk-based evidence to present to production managers when requesting that a well be shut-in.

Following the ISO-14224 standard, iQRA also includes failure data analysis, such as critical failures versus degraded failures. These features have been designed to accelerate the industry shift to risk-based assessment and performance-led decision-making for maintenance scheduling.

These capabilities are already enshrined in UK health, safety and environmental practices, and in Norway, where the Petroleum Safety Authority stipulates that each well workover case be assessed per well and based on reliability data. As regulations evolve, iQRA’s ultimate aim is to equip operators with the insight to optimize well operations by identifying potential weaknesses in their equipment and pre-empting future issues.

Ged Lunt
is technology manager at Wood Group Intetech. Lunt has been responsible for delivering the Intetech Well Integrity Toolkit (iWIT) software for well integrity management to clients including the BG Group worldwide operations, Statoil (2000 wells in Norway), Stogit (ENI gas storage company) and Hess Equitorial Guinea. He has extensive experience in analysis of customer well integrity management requirements, in interfacing database systems into the iWIT software and customizing iWIT to match company requirements.

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