Lessons learned from qualification of 20,000-psi subsea BOP stack

Improved FEA, advanced materials testing and complex multi-party project documentation among key elements of the challenging process

By Jessica Whiteside, Contributor

A step change in BOP history may be arriving with the qualification of National Oilwell Varco’s new 20,000-psi (20K) BOP stack, two of which are set for delivery in 2021, according to a speaker at the 2020 IADC/SPE International Drilling Conference and Exhibition in Galveston, Texas, 3-5 March.

BOPs have been critical to drilling safety for almost 100 years, since the invention of the first ram-type BOP in 1922. The 15,000-psi (15K) models introduced in the 1980s were a boon to offshore development and have marked the outer limit for BOP pressure ratings ever since. But that frontier may be changing soon.

“This will be the decade 20K subsea BOPs are placed into service,” said Bob Cowan, Product Technical Director Offshore at NOV, noting that the product is not just a BOP but a complete stack from riser to well. “The completion guys are working on 20K equipment, the wellheads are already designed and developed, the subsea trees are in place… There’s no reason that this decade can’t see 20K completions come about.”

The advent of 20K BOPs could open some of the world’s most challenging high-pressure, high-temperature (HPHT) environments. NOV designed its 20K BOP for use in extreme high-pressure environments, including ultra-deepwater, with initial deployment expected in 2021 on a 20K well in the Gulf of Mexico.

The 20K BOP is a ram-type model with a drill-through diameter of 18 ¾ in. that can operate in a maximum water depth of 12,000 ft. NOV tested a family of shear, multi and pipe rams for the project, all fully qualified under the latest API requirements. In addition to new HPHT design guidelines outlined in API 17TR8, the project adhered to new qualification procedures from the US Bureau of Safety and Environmental Enforcement (BSEE).

“There’s been multiple technological advances, the standards have changed, regulations have changed, material science has changed,” Mr Cowan said.

Vital to the development of the 20K BOP has been improved finite element analysis (FEA) to understand how a material will react to the loads a component may experience. FEA allows for faster and more detailed analysis, less time required to perform design iterations and a higher number of analyses that can be performed. The data allowed NOV to “do a lot more design work, to be better at it, to understand our materials, to understand fatigue, and to understand design a lot better,” Mr Cowan said.

To demonstrate the extent of these “power analytics,” he noted that the project’s FEA analyses generated 172,127 hours of CPU processing time – equating to 7,172 days or 19.6 years – and resulted in 1.96 terabytes of data.

New frontier requires complex testing

The 20K BOP project had to undertake material testing that Mr Cowan said was not required in the 15K world, explaining that API 17TR8 guidelines for HPHT equipment call for fatigue and material testing, including testing of elastomers that come into contact with the wellbore. The company spent about 15 months testing materials with support from five labs, including in-environment testing involving drilling mud, synthetic-based mud, completions environments and even, for elastomers, a produced-fluid environment.

“As you’re testing, you’re going to find things that you’re going to need to change, but you don’t quit testing; you continue to test so you can gain more and more information to make your product better and more robust,” Mr Cowan said.

For component testing, NOV used a state-of-the-art research and development lab featuring six large-bore BOP bays with 30,000-psi blast-proof walls measuring 30-in. thick. In addition to ambient temperature tests, the lab also provided the ability to test equipment at temperatures below 0°F and up to 350°F, which sometimes required 24/7 monitoring by lab personnel. According to NOV, the validation testing for all components met or exceeded API requirements.

“The current status is all of the products are qualified, and we’re currently testing right now with BSEE on customer-specific items.”

Communication is critical

The task of shepherding such an immense endeavor to completion naturally encountered some bumps along the way. One of the biggest challenges involved communication among the project partners, Mr Cowan explained.

Because BSEE rules for HPHT systems require the submission of a series of reports supporting the project’s conceptual plan, the process necessitated a close working relationship for not only NOV and the contractor but also the operator and an independent third party (I3P). BSEE requires I3P verification reports for HPHT BOP systems and related equipment as part of the Application for Permit to Drill or Application for Permit to Modify.

With each company using operating and documentation systems that did not interface with one another, the 20K BOP team needed to agree on a system for managing the flow of questions, answers and comment resolutions as they built the project documentation.

Mr Cowan recommended that anyone entering into a similar project establish communication protocols upfront, along with a project document controller, to ensure timely review and approval of all the paperwork – especially in light of the huge volume of BSEE documentation required.

“We have submitted well over 3,000 pages of documentation to date, and I’m sure we’ll be submitting more,” he said.

Industry rises to challenges

NOV has already sold two of its 20K BOP stacks to Transocean. In announcing the sale last year, NOV called it “a historic moment for the offshore oil and gas industry.”

How prolific 20K BOPs become – and whether their impact will be as galvanizing as the shift from 10K to 15K – “will largely depend on the success of the first 20K wells to be drilled,” according to NOV’s technical paper, describing the leap to 20K technology as “significant” regardless.

“The design process and testing that we have performed is unsurpassed in our history,” Mr Cowan said. “We have gone through a process that has made us better as a manufacturer, as a designer. The information that we’ve learned we’ve been able to take into other products.”

He said he has seen big technological advances during his almost 44 years in the sector and predicted exciting achievements ahead for those still early in their careers.

“The industry, in my experience in it, has always risen to the challenges placed before it,” he said. “20K is just one those challenges. There will be another challenge down the road.”

New products developed

According to NOV, the 20K ram BOP has complete capability of shearing and sealing the slip-proof section of the landing string of 6.906-in. OD x 3.5-in. ID and 14.15-in. casing 127 lb/ft, in addition to the expected drill pipe to be used in drilling 20K wells.

Other new items specifically developed by NOV for its 20K project include a 20K wellhead connector, 20K subsea valve, 20K riser seals and choke and kill lines, 20K choke and kill connectors, 20K shear rams, 20K multi reams, 20K pipe rams, 20K 18 ¾-in. flange connection and a 5K locking system shear ram with booster.

The technical paper noted the robustness of the new rams tested, stating: “After any test, all ram assemblies (including shear rams) are mag-particle inspected and prepared to be used again in the next test. Throughout all our testing to date, we have not scrapped any ram assemblies and they continue to be used in additional tests.” DC