The Perdido team faced a tough decision. A conventional topsides design required a series of modules that would have to be fabricated onshore, then lifted onto the spar and integrated offshore, but what if the team could constrain the design enough that it could be built and lifted in one piece?
Health, Safety and Environmental (HSE) needs drove the design of Perdido’s topsides. One of noticeable features is the 2.5-bar blast wall that separates the crew quarters from the drilling and processing equipment, but Perdido also has the most aggressive fire suppression and gas monitoring systems of any offshore platform. It is a reflection of how the industry in general is maturing in terms of fire and explosion protection. Planning runs the gamut from how to prevent a release and ignition, to how to mitigate the impact if you do have a fire or explosion, and how best to evacuate the platform.
“Industry has learned a lot, particularly since the 1988 Piper Alpha fire in the North Sea,” Shallenberger says. “If there is a gas release, for example, we now have sophisticated models to help us understand where the gas will go. Perdido has more gas detection than any other platform, probably by a factor of five. If we were to detect gas, we can quickly depressure the whole facility and divert the gas to our flare system.”
The Perdido design team did extensive modeling of the onboard firefighting capability. Perdido’s twin 5,000 gpm firewater pumps and automatic foam system is the most extensive fire protection layout of any Shell platform in the Gulf of Mexico. One revolutionary feature is that the system is automatic. Rather than having a water deluge system and a supplemental foam system, both manually triggered, Perdido’s automatic fire suppression system covers the entire platform, including the heliport.
“Computer modeling also helped us determine, if there were an explosion, what kind of overpressure to expect at various points throughout the facility,” Shallenberger says. “Blast walls shield not only the crew quarters, but also the safety equipment, work areas and evacuation routes. There are no production offices in the process areas, and the Incident Command Center is adjacent to the control room for real-time feedback. We spent a lot of time in the screening process to make sure that in this compact space, our people are well protected.”
Integrating the subsea systems
Perdido’s subsea system, which includes separation and boosting, direct vertical access wells and tiebacks to satellite wells, is a first of its kind.
“Integrating those systems was one of the most complex things we’ve done on this project,” Shallenberger says. “From a topsides perspective, we are looking at recovering oil and gas from a collection of low-energy reservoirs.”
Fabrication sites
Steel and equipment for the Perdido topsides came from around the world. What designers called the box – the structure that was designed to fit the lifting capabilities of the Thailf SSCV – was built at the Kiewit yard in Ingleside, Texas, just across the bay from Corpus Christi. Ingleside is the same facility that completed the spar in 2008. The crew quarters were built at Delta Engineering on the Houston Ship Channel.
Working through storms
Katrina, the most expensive hurricane in U.S. history, made landfall in southeast Louisiana on August 29, 2005. Much of the Perdido team, then in the early stages of design and engineering, was displaced for six months. It was the first big storm to disrupt the project, but not the last.
“When Katrina wrecked the city and Shell’s offices in New Orleans, we moved the Perdido team to Houston,” Shallenberger says. “We began the front-end engineering and design (FEED) process while we were displaced. That was a big issue for our folks, traveling back and forth, fixing our homes on the weekends and coming back to Houston during the week.”
Air logistics
Perdido’s distance from its air and marine base in Galveston, more than 200 miles to the north, means that most service boats are 18 hours away, and even a helicopter transport takes at least 90 minutes. Shell, and many other operators in the Gulf of Mexico are using relatively large helicopters so they can evacuate and service their platforms efficiently.
These bigger helicopters, like the twin-engine Sikorsky S-92, can carry up to 19 passengers, but they need plenty of room and a sturdy landing space. Perdido’s heliport is large enough for two S-92s. It is built of aluminum, and equipped with advanced safety features to prevent fuel fires on the helipad.
Transportation and installation
Since the spar had to be towed to site in a horizontal configuration, the deck and quarters had to be integrated offshore. The topsides sailed from Kiewit’s Ingleside yard on March 8, 2009. The topsides lift was completed on March 13, and the living quarters were added three days later. At 9,773 short tons, the single-piece lift of the Perdido topsides was the heaviest ever in the U.S. Gulf of Mexico.
A model for ultra deepwater
The design of any deepwater project depends on the nature of the reservoirs, water depth, number of wells and a host of other factors. While no single platform can serve every need, the Perdido concept certainly adds new tools to the box.
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