Model engineering for asset integrity

Meg Chesshyre

January 1, 2016

Aging assets and life extension are consuming ever more engineering hours in the offshore oil and gas industry. How can engineering tools help? Meg Chesshyre looks for answers.

Image from Petrofac.

Structural integrity management is a growing area of work on the UK Continental Shelf. With more than 200 installations now over 20 years old, and a number over 30 years old, there are specific challenges in terms of degradation, corrosion and fatigue, which need to be considered as facilities approach the end of their design life.

How to tackle these issues was the subject of a forum session at the Bentley Systems Year in Infrastructure 2015 conference in London this past November. A key theme was being able to reduce offshore hours through engineering by using structural integrity management and tools such as reality modeling to help build as-built models, which can be used for engineering analysis.

For Justin Jones, structural engineering consultant for Petrofac, the value of structural integrity management (SIM), compared to vessel rates, shouldn’t be under estimated. Engineers are relatively inexpensive in comparison, Jones says. “The cost of the hire of a vessel far outweighs our engineering time to demonstrate the integrity of the structure,” he says – 250 weeks of engineering costs about the same as one day of vessel hire.

The use of SIM also enables operators to have a safer structure. “If you fully understand the nature of the structure it can be safer, as well as cheaper to operate.”

Jones gave five case histories of structural integrity management on a string of unnamed projects, all of which resulted in cost savings and life extension for the structures. The first was jacket push-over analysis on a southern North Sea jacket, the second loss of support material on a southern North Sea helideck, and the third, a 10,000-year wave impact assessment on an emergency shut down valve deck (something that would not have been considered at the time of design). The fourth involved fatigue analysis for life extension of a mobile offshore production unit in the Caspian Sea. The final example was of a structure with flaws in it, something that is now occurring frequently in a number of in-service assessments, especially those which have greatly exceed their design life.

It’s not just the age of the assets that is increasing the requirement to get a grip on integrity. Minnie Lu, civil/structural group manager at Petrofac, says new codes and legislation are a lot more stringent than in the past and knowledge around oceanology has advanced, improving modeling. In addition: “With the depressed oil price and squeeze on capital investment in new assets, we are also facing increased pressure on extending the life of our existing assets,” she said. There had also been a shift to risk-based inspection planning as opposed to fixed frequency inspection planning, she added.

Using Navigator i-Model viewer. Image from Petrofac.

Phil Christensen, Bentley’s vice president, offshore and marine, says the US Gulf of Mexico is also having to take into account a changing legislative environment, including the American Petroleum Institute’s recent introduction of recommended practice 2 SIM in relation to the platforms in the Gulf of Mexico. Christensen said there is quite big differences in the approach to inspection in the US and the UK. “The UK is quite far ahead of the game in terms of taking a risk-based approach. In the US it is still mostly time-based inspections,” he said.

There are various reasons for this. The meteorological environments are very different. While there are constant storm loads in the winter over the North Sea, there are very isolated but very intense meteorological events in the Gulf of Mexico. When Hurricane Katrina and Irene went through the Gulf of Mexico there were 60 full platform failures. Also, “people buy and sell platforms all the time in the Gulf of Mexico, so there is less willingness to invest in something that you are going to own for five years, and then pass on.”

Bentley is developing new products to meet the industry’s needs in terms of structural integrity modeling. “We are adopting a ‘model centric’ approach to asset integrity management, he explained. “Because we have a lot of modeling applications, and our i-Model common data environment allows us to bring in models from other systems. This means we can give asset integrity planners, inspectors and engineers a model and graphical context in which to plan and carry out their inspection work as well as to run analyses as a result of the inspections.”

Five of Bentley’s products were listed: SACS for offshore structural and fatigue analysis, ProjectWise for engineering information management, APM for asset performance management, Navigator for information mobility, and ContextCapture for reality modeling, a new industry development as well as a new offering from Bentley, which was announced at the London conference.

ContextCapture is Bentley’s first product release of the Acute3D software technology it acquired earlier in 2015. The software is ideally suited for any organization that could apply 3D models of real-world context to benefit infrastructure design, construction, or operations.

“In situations in which models are not available, tools like ContextCapture are ideal for creating models. I know drones are routinely being used for inspecting hard to get at areas like flare towers. Creating a reality mesh from the photos resulting from those inspections would be very straight forward,” Christensen said. “The notion that you can now go on the platform with a mobile phone and just take photos, and actually get a really accurate, useful 3D mesh, this is really mind blowing.”

But, there are also interesting business issues around where the data lives. Some owners are already all on the cloud; for others data is still on the server.”I would say in five years’ time it will be 80% cloud. It’s an unstoppable challenge,” Christensen said.

Problems being worked on at the moment include adding more ways to attach information. “I think audio attachments are going to be quite useful,” Christensen said. “A lot of the time it is much easier to say the crack is outboard three feet from the end, but you have to look under the bracket to really see it. You don’t really want to try and write that down.”

Foundations for Deepwater Wind’s offshore wind farm near Block Island, designed by Keystone Engineering, and built by Gulf Island Fabrication in Houma, Louisiana. This is the US’s first offshore wind farm. Photos from Keystone Engineering.

Inspired engineering

The winner of Bentley’s 2015 Be Inspired in Offshore Engineering award at the conference was Keystone Engineering. Keystone Engineering has adapted deep water jacket-type support structure design from the oil industry for use on five, 6MW wind turbine generators on America’s first offshore wind farm – the US$290 million Block Island project, which will supply power to Rhode Island and the rest of New England. Bentley anticipates that seven such structures are to be installed off the US Atlantic Seaboard by 2017.