On March 31, 2010, Shell officially brought the Perdido field onstream. Moored in nearly 8,000 ft (2,438 m) of water 60 miles (96.6 km) beyond any other existing development in the Gulf of Mexico (GoM), Perdido is the deepest offshore oil and gas drilling and production platform in the world.

Born smart

Topsides sit dockside awaiting final installation. (Image courtesy of Shell)

According to Robert Perrons, learning manager at Shell, who talked about the Perdido development at the SPE Intelligent Energy Conference in Utrecht, The Netherlands, in late March 2010, “Perdido was born smart.”

Before plans were made for development, the field was screened to evaluate where smart field technology could be applied best, and field-specific solutions became part of the development plan, which looked beyond the objective of putting the field onstream. The intelligent operations (IO) approach to managing the field began with an assessment of the collaboration environment requirements and defined the components that would provide the best environment for success.

A large part of Perdido’s intelligence, Perrons said, is provided by an operating center in New Orleans that allows remotely assisted operations that make it possible for some offshore tasks to be delegated to an onshore facility that brings information and personnel together.

“IO is a loop,” he said. “It goes on for the entire lifecycle of the asset.”

Spar hull construction took place at the Technip yard in Pori, Finland. (Image courtesy of Shell)

With more automation and improved data management, operations are more cost-effective, and more engineering time is available to address non-routine events. This way, Perrons said, “More time can be spent finding ways to wring more value out of the asset.”

Soon remote operations will become routine. “At Shell, all new fields will be born smart,” Perrons said. “Shell is aggressively deploying Smart Fields tools and technologies in a way that makes us quite competitive overall in the digital oilfields area.”

Opening the frontier

FMC provided some of the subsea components used on Perdido. (Image courtesy of FMC)

In a press conference announcing first oil, Marvin Odum, Upstream Americas director, Shell Energy Resources Co., said the Perdido facility has opened new horizons in the GoM.

“This is a new frontier in many respects,” Odum said. “Shell’s team used its expertise to open this new frontier and confront complex reservoir characteristics, extreme marine conditions, and record water-depth pressures. Perdido presented technical challenges unlike any we’ve ever seen in the Gulf of Mexico.”

According to Dale Snyder, Perdido project manager, there were several significant technical challenges in developing the field.

One of those challenges is the reservoir itself. “This is an older geologic horizon in the Gulf of Mexico that hasn’t been tapped into yet,” Snyder explained. “Up until now, developments have targeted the Lower Miocene.” Perdido is the first Lower Tertiary development in the deepwater GoM. As such, “Perdido is a step out for Shell in the industry,” Snyder said.

Not all Lower Tertiary paleogenes are the same, Snyder said, noting that temperatures and pressures are very different depending on where the reservoir lies. Perdido is a highly faulted reservoir, Snyder explained. “We don’t know for certain, but we suspect that it is going to be compartmentalized, so a high well count is necessary to develop the field.”

Drilling a large number of wells can be fairly costly in shallow water. In ultra-deep water, it is extremely expensive.

As water depths increase, the size of the floaters tends to follow suit. “If you look at the fact that Perdido will have 35 wells, you can see how that would drive the size of the structure to be quite huge,” Snyder said. “You can imagine the cost if we had to bring a MODU (mobile offshore drilling units) in to drill each well.”

Normally, if there were 22 wells under the platform, there would be 22 production risers running from the seafloor up to the platform. A drilling rig would have to move onsite to drill or work over the well through each individual riser.

To avoid the huge added cost of contracting another rig, Shell came up with the idea of reducing the number of risers on the platform by using part of the subsea boosting system and comingling all of the flow.

“We have a fully capable drilling system out there, and we have direct vertical access wells on the platform,” Snyder explained. “So although we have 22 wells under the platform, they are all subsea wells with subsea trees, and the production is brought up from five risers instead of 22. So that greatly reduces the payload and the amount of space required for the well systems.”

Another challenge is that the reservoir is very shallow beneath the seabed. “That creates a bunch of problems for us,” Snyder said. “It is hard to deviate the wells and reach all of the targets we want to reach.” In addition, the pressures and temperatures are fairly low. “Getting the reservoir to flow up to a platform through a mile and half of water means you encounter tremendous backpressure just from the risers and the hydrostatic head in the risers.”

Subsea solution

Two issues associated with the reservoir led Shell to employ a subsea boosting system. One was backpressure. The other was that the pressures and temperatures encountered in the reservoir create hydrates in the riser.

“We had to separate the liquids from the gas at the seafloor to contend with the hydrate problem,” Snyder said. The subsea boosting system also addresses the problem of backpressure. “We wanted to pump the liquids from the seafloor up to the platform so the wells could flow productively.”

Production from the wells is comingled at the seafloor. “We actually separate the liquid and gas at the seafloor in the caissons we have set up as part of the subsea boosting system,” Snyder explained.

Two tug boats move the Perdido spar into the GoM. (Image courtesy of Shell)

The industry has been placing multiphase pumps on the seafloor, Snyder said, so the concept is not new. The Perdido system “as a whole” is unique. “To do it in one system like we’re doing is a unique application.”

The caissons used on Perdido are part of the Shell-designed subsea boosting system.

“We built part of the testing program to prove how all of this would work, so we had a multiyear technology development program that was being carried out in parallel with the project,” he explained. This culminated in a full-scale onshore test at Shell’s Gasmer Road research facility in Houston, where full-sized components were built and tested.

During the tests, oil and gas was run through the full system to make sure the process would work. “The design of the caissons was part of that,” Snyder said, explaining that the good thing about building the full-scale operating components and running tests is that Shell learned a fair amount about how to operate the system, which affects how the system is designed.

The subsea separation system is made up of a 350-ft (106.7-m) long caisson that is embedded in the seafloor and topped by an inlet assembly that resembles a subsea tree. As the flow comes in the inlet assembly from the wells, a cyclonic action in the assembly rapidly circulates the flow, creating centrifugal separation of the liquids and the gas. When the stream is separated, the gas flows up the riser naturally, and the liquids drop into the caisson, where some additional gravity separation of the gas from the liquids takes place.

“We need to control the level of the liquid,” Snyder explained, “so an ESP (electrical submersible pump) is placed at the bottom of the caisson.” Full-scale testing allowed Shell to investigate how to speed up or slow down ESPs and how the control systems should be manipulated to measure where the liquid level is in the caisson. Testing also allowed Shell to investigate methods of dealing with foaming and how to define the gas/liquid interface. “A fair amount of testing was required to see if it would work and how we could tune it, instrument it, measure it, and control it so that it would work properly offshore.”

Intelligent management

Perdido, the deepest offshore oil and gas drilling and production platform in the world, came onstream March 31, 2010. (Image courtesy of Shell)

Now that Perdido is onstream, the time has come to reap the benefits of creating it as an intelligent field. Much of the day-to-day activity can be monitored remotely, Snyder said. “There is quite a bit of data coming in. We have multiphase flow meters and ESPs subsea, and our entire topsides uses a very complex distributed control system. Our subsystems are integrated as well.”

Shell has the capability to see all of the data in its control room in New Orleans, which mirrors the platform. The collaborative work environment onshore allows experts to view production data remotely and to solve any problems that arise in real time. This approach, which has been employed successfully on other Shell developments, will allow the operator to monitor Perdido much more closely.

IO has also improved safety. “Perdido’s fire detection system features a completely automated high-capacity water and foam deluge system with sensors that allow the system to automatically respond when a fire occurs,” Snyder said. All of the instrumentation and controls can be rolled in and activated without endangering personnel.

Safety is one of Snyder’s top priorities. “The one thing I am extremely proud of is that when we set out at the beginning of the project with all of these challenges, we decided the most important thing we were going to focus on was HSE. Our goal was to execute this project without anyone getting hurt. I’m proud to say that we got to first oil with no lost time accidents in the entire project, which amounts to 10.5 million man hours. I think that’s a real testimony to the commitment of the people on the project and our leaders to really make that happen and to keep that our focus.”

Today, with first oil achieved without incident, Perdido has set another industry milestone, and Shell is justifiably proud.

Snyder, meanwhile, is keeping his eye on the job: “We’re producing our first well. We’re running our subsea boosting systems. We’re making minor adjustments. So far, so good.”