Ensco adds mooring capabilities
Offshore drilling contractor Ensco seized an opportunity to offer its customers a wider range of drilling services, at various water depths, by retrofitting mooring systems onto two of its ultra-deepwater semisubmersible rigs.
With the addition of mooring capabilities, theENSCO 8503 and ENSCO 8505 are now capable of operating in DP or moored capacity for both drilling and intervention work in deep- and shallow-water areas.
This added capability has proven to be especially important at a time when in spite of limited drilling opportunities in the Gulf of Mexico, operators have been taking advantage of the market downturn to perform intervention and plug and abandonment (P&A) activities. The operational flexibility of the two upgraded semisubmersibles has been a key factor enabling Ensco to secure contracts from Marubeni Corp. and Stone Energy Corp. as well as sublets from Apache and Chevron for this type of work thus far in 2016.
TheENSCO 8503 and ENSCO 8505 are part of a series of ultra-deepwater rigs delivered between 2008 and 2012, six of which secured long-term contracts in the Gulf of Mexico immediately upon their delivery.
As the drop in oil price started putting pressure on the rig market around the middle of 2014, Ensco identified an emerging need for rigs capable of handling hybrid work ranging from ultra-deepwater drilling to well intervention and P&A across a much wider water depth range.
“We had been doing some acid stimulation work on a number of wells for one of our customers,” explained Jason Morganelli, VP-Marketing, Western Hemisphere for Ensco. “The customer said that we were well set up for this type of project and suggested we consider more intervention work.”
The decision to add moorings to these sixth-generation DP rigs came not only in the wake of the market downturn, but also in the context of changing regulatory requirements.
In the wake of Hurricane Katrina, regulators increased mooring system requirements. “The new standards meant that it took a lot longer to perform the mooring operations,” said Morganelli, “and additionally, whenever a storm entered the Gulf, rigs without self-propelled DP capabilities had no option but to shut down and evacuate.”
Also, many of the older rigs that, on the one hand, were capable of operating moored in shallow waters, were on the other hand technically challenged to meet the new drilling standards that took effect following Macondo. This created an opportunity for high-specification rigs capable of drilling in shallow waters, and indeed “several operators approached us asking if we could use DP to drill wells in 1,200 ft of water,” Morganelli said. “This prompted us to devise a solution.”
Stone Energy recognized the need for additional capacity in the moored arena, says Craig Castille, director-deepwater drilling & completion. “We wanted to have a rig that could operate in all of our water depths. We opted to go with the Ensco rig that had been upgraded. The quick-release system, which allows the rig to disconnect from its mooring and sail away under its own DP power, had advantages.”
Chevron, another GoM operator, also recognized the value of a moored semi. “Ensco’s decision to retrofit two of its 8500 series rigs was very favorable for Chevron, as the timing was ideal,” said Ken Leblanc, senior drilling superintendent-GOM asset development area, Chevron. “The execution of the rig was excellent, especially the mooring performance.”
Increasingly, as Ensco realized that a number of its clients had programs that called for multiple re-completions, P&A’s, and drilling in both shallow and deepwater areas - it became evident that a highly capable moored semi was needed in the Gulf of Mexico. “We knew that ENSCO 8500 Series rigs were ideally suited to tackle this type of work, given their track record of being the first rigs permitted to go back to work in the US GoM after Macondo and still hold the record of the deepest well drilled here,” Morganelli said. “It took only minor modifications to equip two of these rigs with a mooring system, therefore opening up a new niche in the market for us.”
|ENSCO 8503 semisubmersible rig. (Photos courtesy Ensco)">|
|TheENSCO 8503 semisubmersible rig. (Photos courtesy Ensco)|
The ENSCO 8500 Series rigs had originally been outfitted with four mooring winches. The concept was to double the mooring capacity in order to meet the local environmental criteria, and Ensco engaged in a feasibility study with the Bureau of Safety and Environmental Enforcement in order to secure approval for its proposed upgrade.
“Given the rigs’ existing four anchor winches, the upgrade involved adding four more that would use the same infrastructure - the same power, cooling water, hydraulics - all the things you need to run an anchor winch,” Morganelli explained.
To reduce the time required to perform mooring operations, Ensco adopted a pre-set mooring system and installed the remote-operated quick-release devices. “In the event of a storm for instance, crews can activate the quick release, leave the pre-sets on the ocean floor, and evade the storm just like any other DP rig in the Gulf of Mexico,” Morganelli observed.
With the upgrade, the two Ensco semisubmersibles can work in water depths ranging from 450 ft to 8,500 ft. “We call it an advanced hybrid solution,” Morganelli said. “We have a sixth-generation, deepwater DP rig that can also complete projects in shallower waters using the mooring system.”
Another key advantage for these semis is their deck space. “The rigs have a ‘Texas sized’ open-floor plan design with plenty of space for different types of equipment,” Morganelli explained. “That means we can work with most customers without having to make many modifications.”
That open deck space makes it easier for crews to switch over operations from drilling to intervention to P&As. “In this business, time is money,” he observed. “Your ability to conduct operations more efficiently, concurrently or even off the critical path, is a real differentiator.”
Additionally, the ENSCO 8500 Series rigs were originally constructed with a subsea tree-handling system targeting development drilling activities where trees are deployed onto the well upon completion. Today, the tree-handling system on these rigs also enables Ensco to remove the trees as part of its overall P&A capabilities.
“We have a one stop shop solution for the customer,” Morganelli said. “So when the rigs are operating in shallow water, they’re in a moored configuration. Then when they are in deeper water, we revert to full DP mode. Our rigs can address customers’ offshore leases that straddle the vast majority of all water depths,” he noted.
|ENSCO 8505 semisubmersible rig.">|
|TheENSCO 8505 semisubmersible rig.|
As evidence of these unique capabilities, theENSCO 8505 managed to cut down its work program with Marubeni in the US Gulf by over 30% from the original plan.
Marubeni had several different objectives they wanted to accomplish. These included nine P&As in roughly 7,000 ft of water as well as drilling prospects in 1,500 ft of water. In the past, this type of program would have meant hiring two different rigs to perform the work. But with the upgradedENSCO 8505, Morganelli observed that “the operator gets the benefit of continuity. They mobilize and outfit one rig for their entire campaign - all their third-party equipment and communication systems are installed at one time.”
Stone Energy used theENSCO 8503 for light well intervention on its Pompano project, “and it performed well,” Castille commented. “It allowed us to plan new intervention work that cannot be performed from a monohull vessel. With this type of rig, we can perform wireline, slickline, or coiled tubing methods. With the upgraded ENSCO 8503, we have a lot more capability, and can do things more efficiently from one rig.”
Having a single contractor for light well intervention is much more efficient from the operator’s perspective, Castille noted. “It’s more efficient, and gives operators some flexibility to enter the well. We would not have had this flexibility with a multiservice vessel.”
“Chevron deems the enhanced retrofits performed by Ensco on its 8500 Series semis as a viable option for its intervention work in the GoM,” said LeBlanc. “As opportunities arise, Ensco will be a strong candidate for this type of work.”
“A shallow-water moored rig with high capability performance changed the performance curve, an offers a much more efficient option than older rigs,” Castille added. “For drilling and completion, it will be able to drill deeper and faster than other rigs. So, going forward, these rigs will have a niche in shallow water.”
Given the vast productivity of the Gulf of Mexico over the past 60 years, there are a growing number of idle wells that need to be capped, and operators are taking the opportunity that the downturn presents - when less exploration drilling is taking place - to decommission platforms and P&A wells.
“The intervention market is a niche market that we have been able to exploit at a time when there isn’t a whole lot of drilling taking place in the US Gulf,” Morganelli observed. “The Gulf is a mature market, and there will be a lot more of this work needed even when the market improves. At the moment, it is about bringing the most versatile, cost-efficient solution to the operators, and our upgraded ENSCO 8500 rigs have demonstrated they can be that solution.”