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Cheaper subsea fabrication moves a step closer

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Gustav Heiberg Gustav Heiberg
Business Development Leader, Materials, Høvik, DNV GL - Oil & Gas
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subsea forgings
Large reductions in subsea project costs are goals of Recommended Practice DNVGL-RP-0034 for subsea forgings
Harmonizing oil and gas industry requirements for steel forgings would enable more consistency and repeatability, and better quality of components vital to the safe, clean and efficient functioning of subsea equipment.

“This is really about efficient project execution,” said ExxonMobil’s Dr Brian Newbury, speaking as chair of a DNV GL-led joint industry project (JIP) that is complementing Recommended Practice (RP) DNVGL-RP-0034 Steel forgings for subsea applications. The RP is aimed at reducing delivery time, engineering and production costs, and at improving material quality of forgings.

Newbury explained that large forgings are typically “the pacing item” for subsea tree delivery. If a tree is delayed, there can be significant knock-ons for overall project execution. Drill rigs often run USD1 million or more per day, and drilling costs are typically the largest portion of a subsea project budget. The efficiency of contracting, mobilization and rig utilization decides if a project comes in on budget therefore.

“If operators cannot optimize drilling schedules, or have to mobilize or demobilize rigs due to subsea equipment availability, there are huge negative amplifying effects well beyond the price of a subsea tree, much less an individual forging,” he added. “Previously, vendors have had limited pre-stocking programmes due to variability in what operators required in both material specifications and quality oversight.”

Hans Christian Ly, head of materials technology for global engineering contractor Aker Solutions, put it another way: “Harmonized requirements would reduce cost levels as we could trust that the industry would use the RP, which will then gain higher volumes.”

Accordingly, Phase II of the ongoing JIP aims to establish harmonized quality management and surveillance requirements for forgings to support further the stocking philosophy. This phase is expected to be completed in December 2016.

By spring 2016, Aker Solutions was among the majority of JIP participants who have implemented the RP. “We have used it to standardize our set-up of materials in our enterprise resource planning system,” Ly said. “When a project comes up, we are prepared to use it.”

Progress on quality requirements shows participating operators, vendors and forgemasters aligning with the goal of consistent levels of quality oversight, Newbury reported.

“This is an important accomplishment,” he commented. “Achieving alignment from the major operators to remove direct oversight of critical forgings manufacturing, coupled with vendors’ and forgemasters’ commitment to provide consistent quality oversight across the industry, enables this strategy. We are currently working to define these quality requirements for qualification of forgemasters and production surveillance.”

Solving the trust challenge
Ly identified trust as a key challenge to the RP becoming more widely adopted in the industry. “We still need to build more trust into the supply chain. Otherwise, we could see the number of hold and witness points, and documentation, remain as high as today.”

A hold point halts fabrication work for obligatory verification to see that quality matches specification. Fabrication can continue during a witness point, but cost is incurred if an inspector is assigned to check on work processes and methods.

“It can take eight to 10 months between order placement and delivery of a forging to equipment manufacturer; this should be only two to three months,” noted DNV GL’s Morten Ro Helsem, who project manages the JIP.

Newbury sees three main challenges to effective implementation of the RP.

The first of these challenges is a need for increased standardization among vendors and operators on equipment design. This would minimize the number of different forgings required for a given type of subsea equipment, and increase flexibility in the supply chain.

The second challenge is that vendors need to demonstrate in practice a stated willingness to share forgemaster qualifications. This would minimize repeated work required of forgemasters. Challenge three is for operators and vendors to adopt consistent steel forging classes of equipment and parts so that forgings become truly standardized.

He ended optimistically: “Efforts such as this JIP are essential in economic environments that we as an industry currently are experiencing. Realization across the spectrum from operator to vendor to forgemaster that increased efficiency benefits all parties is evidenced by the number of companies implementing DNVGL-RP-0034.”

Flow centre takes on more subsea testing work

DNV GL’s Flow Centre, UK, one of the world’s largest natural gas test facilities, derived nearly a third of its 2015 revenue from subsea testing. Connected to the national gas transmission system, it uses dry gas at pressure, and flow rates up to 19,500 actual cubic metres per hour.

It tests components across a range of sizes, and can handle weights exceeding 20 tonnes. These include flow meters, filters, turbo expanders, new meter and hot tap technologies, pipeline internal coatings, and choke, downhole safety and gas-lift valves.

Three examples of testing include downhole safety-valve performance and closure; performance of gas-lift valves; and calibration of subsea meters so new wells can be tied into existing pipelines.

“Challenges around safety, increased oil recovery, and utilizing existing infrastructure are driving subsea testing business for us,” said Dave Shepherd, Flow Centre manager, DNV GL - Oil & Gas.

Disclaimer: 

DNV GL prides itself on providing accurate information but makes no claims or guarantees about the accuracy, completeness or adequacy of contents in this publication, and disclaims liability for any errors or omissions. The authors’ views here do not necessarily reflect DNV GL’s views.