Contractor goes inside well to slash cost of deepwater P&A
A Houston company claims to have achieved a breakthrough in deepwater plugging and abandonment by combining its existing well-intervention solution with a riserless internal-cementing tool.
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Wild Well Control used this strategy to plug and abandon (P&A) a well at 7,200 feet (2,200m) in the Gulf of Mexico in January, Martial Burguieres, Vice President of Marine Well Services, told DecomWorld. It repeated the feat at 7,105 feet in March, and is working on a third P&A at 6,800 feet.
The system combines two proprietary technologies: the 7 Series Intervention System, named for the well bore’s nominal diameter in inches, and the new DeepRange Cementing Tool. “The principal advantage to a system like this: it’s faster to run… We don’t cut and pull or mill the casing,” explained Burguieres.
Inside job
Wild Well’s system uses modular equipment that is lowered onto the wellsite from any vessel with at least 4,500ft2 (418m2) of deck space and capable of operating a heave-compensated 60-ton crane. If a pressure test fails, there is no costly, slow-to-deploy marine riser or blow-out preventer, which can take days to bring back on board and troubleshoot, Burguieres explained.
The 7 Series methodology was originally tested on eight wells in Angola, in water shallow enough to have divers perforate the outer annulus from outside the wellhead. The system is certified to 10,000 ft and 10,000-psi working pressure, and is compliant with the American and British offshore regulators, and with the standards set by DNV GL and other industry classification bodies.
By bringing in the DeepRange, Wild Well was able to conduct the entire operation “inside the well, under well control – so we’re not hot tapping, or perforating outside,” he added. Although the DeepRange technology can be deployed with just a small vessel, the option is there to use a semi-submersible rig – which Wild Well opted for in January when day rates where suitably low, noted Burguieres.
Either way, Wild Well is confident it has found a way to reduce the cost of P&A significantly.
“The average [traditional] P&A cost – and it’s hotly debated – is $40-60 million per well. There have been ones that have gone way above that, and some that you hear rumors being a little less,” said Burguieres. “Our target was $12 million total cost. We didn’t quite hit that but we’re trending toward it. We exceeded it, but not by a lot.”
Technique revealed
Wild Well crews begin the P&A by performing a temporary abandonment of the well, cutting and pulling the tube before installing a cast-iron bridge plug in the production casing on electric wireline (e-line).
A series of perforating guns, one installed on a tubing string as part of the P&A tool and one run on e-line, are used to perforate the production casing above and below a special packer assembly. The perforation gun’s charges are precisely calibrated to prevent a compromise of the next level of casing, Burguieres said, taking into account the possibility that the casing may have shifted through the annulus – eliminating its void on one side – or that there may be corrosion that has significantly weakened the casing.
Circulation is established through the tubing, into the lower perforations, up the B annulus, out through the upper perforations, and back up the production annulus. A resin lead followed by cement is circulated into the B annulus. After the cement cures, the B annulus is pressure-tested and the top-of-cement is tagged in the production casing, in accordance with Bureau of Safety and Environmental Enforcement (BSEE) regulations, explained Burguieres.
Next, the perforating gun is detonated above the packer in the C annulus, creating holes through the production and the surface casing, and creating a fluid path to the C annulus. The perforating gun is then run on e-line, below the lower packer and detonated, creating holes through the production and surface casing into the C annulus. Circulation is again established down the production casing and up the C annulus, taking returns to the vessel.
A resin lead is pumped, followed with cement into position establishing a balanced plug in the C annulus by production casing. The C annulus resin and cement plug are tested, said Burguieres. A plug is set in a profile below the packer, which turns it into an additional mechanical barrier. The P&A retrieving tool is run on the crane wire and the P&A tool assembly is released and recovered to the surface. A cast-iron bridge plug is run into the production casing “open-water” and set above the upper perforation holes. Cement is dump-bailed or spotted on top of the plug.
The subsea well is properly plugged and abandoned in accordance with BSEE regulations, including annular cement requirements, said Burguieres. The well is then fully plugged and abandoned to satisfy “annular isolation” regulations.
By Fred Seelig