Thunder (Horse) rolls

Audrey Leon profiles the Thunder Horse field, speaking with project manager Steve Raymer about the BP-operated field’s most recent expansion project, which came in 11 months ahead of schedule and $150 million under budget.

Loading Pipeline End Termination (PLET) system onto Technip’s Deep Blue vessel. Photos from BP.

This year is set to be an exciting one for BP. The firm is looking to bring seven projects online in 2017. One project, the Thunder Horse South Expansion (THSX) in the deepwater Gulf of Mexico (GoM), was originally slated for start up in late 2017, but it had the good fortune to come online earlier than scheduled, due to good planning and execution.

The THSX project is expected to boost production at the Thunder Horse facility by an estimated 50,000 gross boe/d.

BP achieved this with the installation of two new 11,000ft flowlines, and a four-slot manifold, which creates a new subsea drill center (No. 45), 2mi south of the Thunder Horse platform.

The THSX project started up in December 2016, 11 months ahead of schedule. BP saw US$150 million in savings on the $1 billion project. Bringing a project online quickly and cost-effectively is quite a boon in today’s low oil price environment. These kinds of numbers are positives that plenty of oil and gas firms will want to replicate.

BP acknowledged the success the firm has had at previous GoM projects, such as its Kepler field, which ties back to BP’s Na Kika platform.

“We are also making significant progress in exploration by shortening our cycle time from discovery to production on some of our latest discoveries,” said CFO Brian Gilvary in BP’s 3Q 2016 analyst call. “Our Nooros discovery in Egypt was on production two months after discovery and Kepler-3 came online within 11 months of discovery, which is faster than typical GoM developments of this scale.”

The main drivers for bringing THSX online ahead of schedule and under budget were standardization, cooperation between suppliers and contractors, and great planning and coordination on execution efforts, says Steve Raymer, THSX project manager, BP.

Helix Energy Solutions’ Grand Canyon II (left of Thunder Horse) and Technip’s Deep Blue ultra-deepwater pipelay vessel (right) during in field SIMOPS.

The field

While Thunder Horse is one of BP’s largest fields in the GoM, it hasn’t been the easiest to develop. This is owed to its complex geology and mother nature’s whim.

Discovered in July 1999, BP did not bring the field into production until 2008, three years after its initial target, due to issues stemming from a direct hit by Hurricane Dennis (2005).

BP operates Thunder Horse (75%) along with co-owner ExxonMobil (25%). The field sits inside Mississippi Canyon blocks 778/822 in the Boarshead basin, 150mi southeast of New Orleans in water depths ranging from 5800-6500ft.

Thunder Horse consists of two adjacent fields (North and South) with reservoirs in the Upper Miocene turbidite sandstones. In BP’s fact sheet on the field, the company calls the wells required to access the reservoirs, “some of the most challenging and deepest in the Gulf.”

The development consists of subsea wells producing to a permanently moored, floating semisubmersible production, drilling and quarters (PDQ) facility. The PDQ, which is BP’s largest facility in the GoM, is taut-wire moored in 6300ft water depth. It has 250,000 bo/d and 200 MMcf/d of natural gas processing capacity, and accommodation for nearly 300, BP said. Oil and gas is exported through the Mardi Gras Transportation System.

BP awarded FMC Technologies a frame agreement in 2001 to provide the field’s subsea production system, which is designed for 350°F and 15,000psi and operated via an electro-hydraulic controls system. The field has 5in x 2in conventional subsea trees and manifolds. Round-trip pigging capability is incorporated into the manifold architecture, FMC (now part of TechnipFMC) says.

At Technip’s 60 acres (24 ha) spoolbase facility, south of Mobile, Alabama, sections of pipe, 10in (25cm) in diameter, and more than 1in thick, were welded together to form the two 11,000ft (3350m) flowlines, which were then spooled onto a reel on the Deep Blue’s deck.

Geology

According to a 2010 OTC paper on Thunder Horse, some two-thirds of the oil in place is in the South with one-third in the North. North and South share a common aquifer in the syncline separating the two regions, says Arnold et. al.

The paper describes Thunder Horse South as a large 4-way dip closure that begins at approximately 20,000ft true vertical depth subsea (TVDSS) and persists to 30,000ft TVDSS. Arnold et al said that half of the closure lies below a thick salt canopy.

Arnold et. al describe Thunder Horse North as a large 3-way dip closure against a near vertical salt stock. The paper says that there is a high degree of lateral stratigraphic and structural segmentation. The closure lies below the salt canopy, which also results in poor imaging (similar to Thunder Horse South).

Multiple stacked reservoirs are found in Miocene age sandstones on both the North and South fields, the paper states, which are grouped as Pink, Brown, and Peach stratigraphic intervals.

“Not all of those are developed at every drill center in the North or South,” Raymer says. “By and large, the North is Pink and Brown, and the South is Brown and Peach.”

Raymer says that the sections grouped as Pink, Brown and Peach denote different reservoir sections, depths, pressures and hydrocarbon composition. “They have different properties that result in different production,” he says. “They can all mix together and produce together. Part of the beauty and part of the challenge is developing those three different reservoir sections.”

The ROV control room aboard the Thunder Horse platform.

Field improvements

Since start up in 2008, BP has steadily worked to improve production from the field. In May 2016, the supermajor started up a water injection project on the North field, with the goal of extending production life and recovering an additional 65 MMboe.

Aimed at Thunder Horse’s North Pink geology, the water injection will boost overall recovery within that section of the field, Raymer says.

“It’s always been in Thunder Horse’s long-term plan to have water injection as part of the overall development concept to deliver full recovery from the field,” he adds. “We are seeing a good response from the project and we’re very happy with it.”

Expansion

Raymer says that when the Thunder Horse field was initially developed, BP knew to provide for future expansion.

“When we first sanctioned Thunder Horse, we knew it would be a massive field,” he says. “We put the infrastructure in to initially develop a good chunk of that. And, while we did that, we also recognized that we didn’t have perfect understanding of the reservoir.”

Raymer says that, as time has gone by, and BP drilled more wells in the South, the firm increased its knowledge about not only the size of the reservoir, but how best to develop it.

“It became clear that the most economical way for us to [develop it] was to add another drill center and expand an area of the field that we called South Expansion, to tie into the existing infrastructure, using the expansion capability that we built in initially,” he says.

Part of what made the THSX project so successful is the use of standardized components and working with contractors who had previously provided equipment on the field.

Raymer says that for THSX, BP wanted to use what Thunder Horse already had. “We had an existing subsea tree design,” he says. “All we had to do was call FMC Technologies and order a few more. We had existing subsea equipment, the same manifold design. We did not redesign anything from scratch where we had the opportunity to use something that we already had.”

The project came together quickly. Raymer says BP ordered its first long-lead equipment in August 2014, taking delivery of most of that equipment around August/September 2016. “We installed the majority of that equipment toward the back end of 2016 and we brought production on in December.”

In 2015, Technip, prior to its merger with FMC Technologies – another supplier on the project – was tasked with design, engineering, fabrication, installation and pre-commissioning of the new production pipeline systems on THSX. The project scope included: project management and engineering; coating, fabrication, installation and permanent anchoring of two rigid, 3.25km production flowlines, each with four pipeline end terminations; pre-commissioning and testing. Technip’s ultra-deepwater pipelay and subsea construction vessel, Deep Blue, handled offshore installation work.

Deep Blue unspooled and lowered the two new flowlines to the seabed over a period of eight days, with the help of Helix’s Grand Canyon II, to connect the existing drill center below the Thunder Horse platform with the new drill center, according to BP Magazine.

Grand Canyon II assisted with the pull-in operations as well as pre-commissioning work for the flowlines once they were installed on the seabed.

BP also used the subsea construction vessel, Siem Stingray, to install the rest of the subsea equipment including production manifolds and jumpers.

Overcoming challenges

One major hurdle that plagues most large-scale developments is the scheduling of simultaneous activities. Raymer said that the THSX project came together because of good communication and well-coordinated project execution.

“There was a high amount of SIMOPS (simultaneous operations) going on in the field while we were doing our construction,” Raymer says. “The Thunder Horse asset itself was drilling a well as well as producing. We had [Transocean’s] DD3 [Development Driller III] drilling our first South Expansion well at drill center 45 – where we were putting all the expansion equipment.”

Raymer adds that while those operations were going on, Technip was in the process of laying the flowlines with Deep Blue.

“Just in that time frame alone in summer 2016, we had three extremely valuable assets working together in close proximity, and we were able to complete all that construction work without disruption to the ongoing production and drilling activities that were occurring simultaneously,” Raymer says. “While it certainly was a big challenge, it was also our greatest success as a project to be able to deliver that work safely, without incident and without any disruption to operations.”

Planning played a big role as well in executing the project’s SIMOPS.

“We did an enormous amount of upfront work,” Raymer says. “We employed some 3D modeling techniques to explicitly map out and model the paths that the flowline installation vessel would need to take. We did similar 3D models showing any required offsets or movements that the drilling rigs might need to do while operating.

“Once we had all that technical information, then, the bulk of the work from that point is communication, and regular engagement sessions with the leadership and the operations managers of each of the different assets coming together, and being very clear on the roles and responsibilities on the execution plans and on the scope of work, and the timing that we were all going to follow to orchestrate the execution of all this activity.

“That coordination was a major driver towards us being able to deliver the project 11 months ahead of schedule,” Raymer says, adding: “Being able to do all those things simultaneously (flowline, subsea equipment construction and installation at the same time as drilling and completions of the wells), made the execution extremely efficient versus having to do all those things one at a time, in a series.”

Of course, another potential challenge, like with any offshore project in the GoM, is mapping out a window to execute work before the worst of Hurricane season. BP is famous for its severe weather assessment team, which boasts a team of meteorologists who keep tabs on GoM storm conditions.

For the THSX project, BP ran into a spot of good luck due to a relatively mild 2016 hurricane season.

“We specifically aimed for and targeted a window of opportunity that was right before the start of hurricane season,” Raymer says of the THSX project. “We were able to get this flowline installation done in the late July/beginning of August time frame. And that was before the active part of hurricane season, allowing us to minimize that risk.

“If there had been a storm that had come through, during that time, we had contingency plans in place to be able to postpone and re-assemble post-event as necessary. But, fortunately, that wasn’t the case for us.”

What’s next?

Raymer says that BP expects to see an increase of 50,000 boe/d at the field. “We have two of our four wells online, at this point, with the third currently being drilled (by the West Vela),” he says. “The fourth is in line to be done after that.”

BP expects full production to be achieved at THSX in 2019. 

Work cited

Arnold, G., Cavalero, S. R., Clifford, P. J., Goebel, E. M., Hutchinson, D., Leung, H., … Grass, D. B. (2010, January 1). SS: Thunder Horse and Atlantis Deepwater Frontier Developments in the Gulf of Mexico: Thunder Horse Takes Reservoir Management to the Next Level. Offshore Technology Conference. doi:10.4043/20396-MS