It's time for oil and gas to embrace the cost benefits of non-intrusive inspection
9 Apr 2018
Oil and gas operators are missing a prime opportunity to save on downtime inspection costs yet still do the job properly, says ABB’s Troy Stewart.
By not embracing non-intrusive inspection (NII) for their pressure vessels, oil and gas operators in the UK continental shelf (UKCS) are leaving some £242 million per year on the table: £101 million in deferred revenue and lost production along with £141 million from inspection cost savings
Historically, UKCS operators have undertaken their statutory obligations to examine pressure vessels through internal visual inspections. Vessel shutdowns incur high costs through lost production as well as inspection and reinstatement expenses – not to mention safety considerations.
However, while there is a statutory requirement to periodically check pressure vessels for possible degradation which might interfere with safe and reliable performance, current legislation does not specifically require entry into the vessels to carry out the examinations.
All that is needed is for the chosen method to be proven at least as effective as an intrusive inspection. Fundamental to this is to identify what the damage mechanisms are, where they occur and their expected progression rates.
Analysis suggests that, in up to 80% of cases, advances in NDT make it possible to do these inspections without taking vessels out of service
Risk-based inspection techniques, already adopted by most UKCS operators, provide an effective means of doing this. Once identified, assessments can be made to see if it is possible to detect all these mechanisms externally using non-destructive-testing (NDT) technology.
Last year, with the Oil and Gas Technology Centre (OGTC), we conducted research into NII’s applicability within the UKCS. The analysis suggests that, in up to 80% of cases, advances in NDT, particularly ultrasonic techniques, make it possible to do these inspections without taking vessels out of service.
Known as non-intrusive inspection (NII), this approach is commonly used in mainland UK process industries where it has provided significant financial benefits without compromising safety. NII allows pressure vessels to be inspected with the equipment online and avoids entry into confined spaces to perform the investigation.
In addition, through our research, we estimate that NII can reduce turnaround (TAR) durations by seven days, by reducing the amount of intrusive work during the event, allowing it where possible to be completed at other times when the asset is online.
If vessels are inspected every five years, this translates into an average production increase of 0.38% per year across the sector as whole. With average oil prices of US$55 per barrel, the 2017 average price of Brent Crude, and UKCS 2016 volume of 630 barrels of oil equivalent, this equates to an annual reduction in deferred or lost production of £101 million.
Conducting NII shortly prior to a TAR is also a useful way of scoping out what repairs may be required and thus assists in efficient planning for such repairs during the shutdown if required.
In addition to the financial benefits of greater plant uptime, potentially hazardous labour access issues are avoided and inspection cost savings are significant. In a typical medium-sized vessel the cost of an NII inspection is around £192,000 less than an intrusive one.
Assuming 919 inspections per year, 80% of which are suitable for NII, this equates to further industry-wide savings of £141 million. Adding this to the production-related savings, this represents some £242 million in savings that operators are passing up by not pursuing NII opportunities more aggressively.
In today’s new normal of ‘lower for longer’ oil prices, can the industry really afford to ignore this opportunity?
Troy Stewart is Head of Oil, Gas and Chemicals Service, UK at ABB