Bespoke work
The MWCC and HWCG capping stacks were just the beginning for Trendsetter. An operator commissioned a capping stack that could operate under a tension leg platform (TLP) along with an Arctic variation.
Conventional capping stacks were too heavy and large to work with TLPs, which typically have several risers extending from the seafloor to the surface.
The operator wanted a compact system with dual rams, rated to 10,000 psi and a 7 1/16 inch bore, which could fit within a nest of risers spaced 20 feet apart. The resulting capping stack has a footprint of nine by nine feet.
The Arctic stack was designed for shallow water and severe cold temperatures. It also needed to be placed over a BOP that was installed below the mudline. This required design modifications to allow a remotely operated vehicle (ROV) to directly access and operate the capping stack.
The industry identified a global need for capping stacks. In 2013, international operators formed the Subsea Well Response Team (SWRP), with a membership roster that includes BP, Chevron, ConocoPhillips, Petrobras, Shell, Statoil and Total.
Led by Shell, the SWRP team contracted Trendsetter for four stacks, of which two are valve-based and rated to 10,000 psi and 300 degrees Fahrenheit (150 degrees Celsius), and two are ram-based and rated to 15,000 psi and 300 degrees Fahrenheit.
Those four stacks were placed in geographically diverse locations – Stavanger in Norway, Saldanha in South Africa, Agro dos Reis south of Rio de Janeiro and Singapore.
Around the same time, Wild Well Control entered the international arena, requesting a 15,000psi ram-based stack that could be positioned in Singapore.
By this time, Morry says, “we’re back to peacetime. We were slowly making modifications and enhancements to the existing stacks. The rapid response requirements to obtain hardware to get permits to drill was over with at this point. The dust had settled.
“We had study groups and mutual aid agreements. You’d think the market was saturated. I thought so, and I was one of the guys building these things.”
An operator came calling once again, this time asking for a 15,000 psi, 400 degree Fahrenheit (204 Celsius) stack. The operator had identified a reservoir that might exceed the 350 degrees Fahrenheit (177 Celsius) limits on the recently upgraded MWCC capping stacks.
“The industry had slowly been upgrading the hardware from 250 to 350,” Morry says. “The problem with a 400-degree Fahrenheit-rated capping stack is you can’t just go get 400-degree-rated gate valves or 400-degree-rated BOPs or 400-degree-rated chokes. This was an engineering exercise. This went beyond calling people up and asking if they had chokes or gate valves in inventory.”
Trendsetter Engineering worked with Advanced Technology Valve, Cameron, GE, GE-Presens and Sonardyne to get components suitable for the new temperature requirements.
“Under the tutelage of a major operator, we were able to qualify all the necessary components in record time and meet the project timeline requirements,” says Morry.
The MWCC, which now also includes Anadarko, Apache, BHP Billiton, BP, Hess and Statoil, asked for a 20,000 psi, 350 degree Fahrenheit capping stack to be built. Trendsetter began design engineering and hardware qualification in spring 2016 and expects to deliver it in March 2018 to the consortium.
“It’s not hard to envision a capping stack in the near future that is going to have a depth rating that exceeds what’s out there.” Everything built to date is rated to 10,000 feet water depth, but there are prospects in 12,000 feet and 13,000 feet of water.
Morry says it may come as a newbuild, or it may be possible to re-rate or re-qualify the existing units.
Remote locations
While there are now several capping stacks “ready for installation at any time that can be placed on a boat and shipped offshore in a very quick and orderly fashion”, as Domangue says, demand is still out there.
As Morry notes: “You would assume the industry is saturated with stacks now. Why do we need another stack?”
The answer is that remote locations pose thorny logistics issues. The SWRP stacks can be shipped by air, but, as Morry points out, “the Rock of Gibraltar is air-freightable if you break it down into enough pieces”.
Some of the stacks are very large and require seven or more 747s or three Antonovs to transport to the port of mobilisation. The stacks then require vessels with high crane capacities to install, something not available in all regions.
“It’s pointless to air freight a capping stack to a remote location if you don’t have a vessel with sufficient crane capacity to install it once you get there,” he says.
These two factors mean that in some places, such as the east coast of Canada and the Great Australian Bight, it could take two to three weeks to mobilise, transport and install a capping stack.
“There’s also a perceived hardware gap in response times for the Mexican Gulf of Mexico,” Morry adds.
This is because the stacks that exist in the US are restricted to use in American waters, meaning a response stack for Mexican waters would have to come from somewhere else, likely Brazil or Norway.
“The Mexican Gulf is a remote region because it’s remote to the available capping stack assets.”
Driving force
With the technology to contain a leaking subsea well in place, the key to a successful response comes down to logistics.
“Response time, response time, response time,” Morry says. “That’s the underlying factor. The quicker you get hardware on the wellhead, the quicker you can get it shut in, and the better off the environment is. It all comes down to how you can get it there quicker.”
The estimated response time to East Canada is 15-plus days, to the Great Australian Bight is 20 days or more, and to the Mexican Gulf of Mexico is at least 21 days via marine freight for the heavier stacks.
The latest generation of the subsea capping stack is intended to provide speedy response time in the case of an incident in a remote region.
Halliburton’s Boots & Coots division approached Trendsetter to design and build what became known as the Rapid Cap.
The unit needed to be as compact and lightweight as possible to allow installation with a local vessel.
The entire Rapid Cap response spread, stored configured on pallets and trailers in Houston, fits into two 747 airplanes.
Morry says it can mobilise from Houston to a response operation centre for the Great Australia Bight or to the east coast of Canada in three or four days, and in under five days to an incident well in the Bay of Campeche in Mexico.
The stack is not “geo-fenced” to the Gulf of Mexico, he says, so it can go anywhere it is needed.
Morry calls the system a “culmination of six years of design advances and a better understanding of the operational requirements”, that keeps the complexity to a minimum.
“We went back to the core base requirements — simplicity in function but optimised for flow and mobility.”
The Rapid Cap enables mechanical intervention by ROV. It uses valves rather than rams, which lightens the weight by dropping the need for subsea accumulator modules. It is modular and reconfigured so the individual components could be disassembled.
But its main advantage is speed, he says.
“It’s not a hardware requirement that needed to be filled. It’s a response time that needed to be filled.”
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