Kerr-McGee governs hub-and-spoke system
Jaime Kammerzell, Gulf of Mexico Editor
The Constitution field, in 4,970 ft of water in Green Canyon block 680, will be Kerr-McGee’s sixth spar, its fourth truss spar in the Gulf of Mexico. The company first drilled at Green Canyon block 680 in 2002 and made a discovery with well 680 No. 1. In 2Q 2003, Kerr-McGee drilled additional wells where it hit main pay. The company confirmed the Constitution field with 11 penetrations into oil-bearing sands in seven hydrocarbon-bearing reservoirs. These reservoirs have a porosity of 28%, permeability of 800 millidarcies, and oil gravity of 32° API, the company says. The Pliocene reservoirs occur between 12,500 ft and 15,000 ft deep.
In the 2003 conceptual engineering phase, Kerr-McGee considered floater and subsea well options, Mike Beattie, Constitution project manager, says. But the company went with the truss spar technology they had used previously, which would give them easier access to dry tree wells.
The Constitution field is in Green Canyon block 680. Ticonderoga, which is 5 mi away on Green Canyon block 768, will tie back to the host.
“We went through technical and commercial investigations and ran life-cycle costs,” Beattie says. “Dry trees save substantial operating costs down the road, and when it comes time to do recompletions or an unplanned well intervention, it is less expensive to get into a dry tree well. The reliability and technical competence for that solution weighed in also. We’d already built three truss spars, so we looked at it as lower risk.”
Constitution was to be similar to the Gunnison facility, but the reservoir pressure differences and change in water depth from 3,150 ft at Gunnison to nearly 5,000 at Constitution required dual casing risers, as opposed to single casing risers the company used on the previous spars. Dual pipes in a deeper water depth required higher riser tensions, which is reflected in the increased size of the air cans. Other differences between the Gunnison and Constitution production profiles led the team to make several minor changes on the topsides.
Kerr-McGee and Noble’s 50/50 Ticonderoga discovery on Green Canyon block 768 in April 2004 necessitated even more changes. Not wanting to wait for the production handling capacity to become available based on field decline, Kerr-McGee increased the capacity of Constitution to accommodate Ticonderoga’s additional 30-50 MMbbl, which will tie back to the host.
“It was exciting,” Beattie says, “but it also constituted a fairly major change because we took what was initially a 40,000 b/d oil processing capacity on the topsides and ramped it up to 70,000 b/d, a 75% increase. That was a fairly major de-bottlenecking effort. We added a compressor booster module skid, added miscellaneous equipment, and resized others.”
When Kerr-McGee discovered Ticonderoga in April 2004, it was well into the Constitution project. The operator already had awarded the engineering and construction of the hull and the engineering and delivery of the moorings and riser system to Technip Offshore Inc. and the engineering, procurement services, and project management for the topsides, which Gulf Island Fabrication is building, to Mustang Engineering. Adding Ticonderoga as a 5-mi single tieback with dual flowlines and umbilical was a major addition, at this stage in the project, Beattie says.
Kerr-McGee’s strategy of building relationships with proven suppliers paid off. Mustang was already generating detailed drawings that Gulf Island would use to build the deck, when the operator discovered Ticonderoga.
The Constitution hull is under construction in Pori, Finland. It measures 98 ft in diameter and is 554 ft long.
“Gulf Island’s and Mustang’s cooperative and collaborative effort was just what we had hoped for in terms of expediting certain things the fabricator had to have to advance this portion of the deck,” Beattie says.
Engineering designs, including a major increase to the processing capacity, are complete, and the project is on schedule for topsides completion and load out in 2005.
It’s all in the details
Constitution will have six dry trees, or direct vertical access wells, and an initial two-well subsea tieback from Ticonderoga.
“We have six dry tree wells under the facility to produce Constitution reserves,” Beattie says. “Four of these wells have standard trees capable of producing just shy of 10,000 b/d. The other two are high-rate trees capable of producing up to 10,000-15,000 b/d.”
FMC will supply the dry trees and riser connectors for Constitution under a subcontract from Technip.
Mike Beattie, left, Constitution project manager, discusses the topsides fabrication with Engineering Consultant Steve Pyles at Gulf Island Fabricators in Houma, Louisiana.
The wellheads are tied to the surface with a pipe-in-pipe configuration. The outermost pipe is 12 3/4-in. diameter. Air or buoyancy cans 12 ft in diameter and 200 ft long support the weight of the pipe strings housed in the spar centerwell. Christmas trees are on top of the riser strings to control the well flow.
Technip’s riser product group is designing the steel catenary risers and top tension risers.
“We think it is a big plus when the team responsible for the hull at Technip is in the same building with the riser design team. It is a critical interface,” Beattie explains. “When designing a riser, you have to design it to withstand all the motions the hull will put on it, so we like having those two groups in the same shop.”
Technip designed the nine-line mooring system. The lines consist of seafloor ground chain, spiral strand steel wire, and platform chain to fix the truss spar on location in three clusters of three. Bridon, in Doncaster, England, will provide the mooring wire, and Vicinay in Bilbao, Spain, will supply the chain. Driven pile anchors 228 ft long and 84 in. diameter will secure the lines to the seafloor.
Heerema Marine Contractors will install the piles and mooring system with theBalder. The same vessel will set the hull. Heerema’s Hermod will then set the topsides and air cans.
FMC is building the subsea trees for Ticonderoga. The company supplies a standard 10-ksi Kerr-McGee subsea tree for most of the operator’s projects. Technip will install the pipe-in-pipe flowlines linking the subsea trees to the spar with theDeepBlue installation vessel.
Enterprise will own and operate both oil and gas pipelines. Allseas will install the export pipelines using theLorelay DP pipelay vessel, which will lay the lines on the seafloor in 2Q 2005. Heerema will pick up the lines and hang them off the spar when it is installed.
Originally, the oil pipeline was 14-in. diameter to shelf tie-in point, but the addition of Ticonderoga required an upgrade. Kerr-McGee increased production by 30,000 b/d, so the line size changed to 16-in. diameter.
The oil line goes to a platform in Ship Shoal block 332. At that point, Kerr-McGee has the option of selling into the Cameron Highway Pipeline System or into a future link to the Poseidon Oil Pipeline System. The gas line runs to a subsea tie-in at Green Canyon block 641 near the Typhoon platform and ties into the Anaconda system.
On the horizon
Kerr-McGee is working to finish fabrication of the hull, mooring systems, topsides, and air cans for installation in 3Q or 4Q 2005.
“We are in the field now (March) installing piles,” Beattie explains. “We like to put the piles in early and let them set up. The longer they are in the mud, the stronger they get.”
Kerr-McGee will tie in Ticonderoga after Constitution’s deck is set.
Kerr-McGee is known for its hub-and-spoke developments. Constitution is built to accommodate three additional subsea satellite developments; each with paired flowlines and umbilical.
“We try to get the dry spot out there initially so that we have a base to produce from. Then we acquire other blocks in the area and do subsea tiebacks over the course of the future so we can keep the facility full,” says Beattie.
Many of the opportunities Kerr-McGee has in the areas surrounding the hubs depend on how quickly wells decline and when production capacity becomes available.
“We think we’ll have good production at Constitution, but we are always looking for more opportunities to bring back to it,” Beattie says. “We do have other exploration in the area on the calendar. We drilled a well at the Conquest prospect on Green Canyon block 767 and we are still evaluating the results.”
Location: Green Canyon block 680
Water depth: 4,970 ft of water
Size of field: 110 MMbbl
Operator: Kerr-McGee
Discovered: 2002
Project sanctioned: Jan. 13, 2004
Hull built: Under construction in Pori, Finland
Hull size: 98 ft diameter, 554 ft long overall.
Topsides built: Under construction at Gulf Island Fabricators in Houma, Louisiana
Deck set: Late 2005 or early 2006
