In advance of the Deepwater Intervention Forum this 9-11 August 2016, Jerry Lee reports on a new approach to riserless plug and abandonment carried out by Wild Well Control in the US Gulf of Mexico.
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PA Tool component description and diagram, from Marubeni and Wild Well Control. |
With plugging and abandonment (P&A) projects on the rise and regulations expanding, companies are looking to optimize expenditures whenever possible.
New regulations require companies to isolate and test outer annuli of wells because the annuli between the casings may become leak paths after the well has been abandoned.
To address this issue, Wild Well Control, with support from Marubeni, developed a new riserless P&A approach that is currently being utilized in P&A operations in the Gulf of Mexico on a nine-well campaign. This new approach can be used on either a multiservice vessel or a rig.
“Normally, it’s done by cutting and removing the casings; I don’t have an inner annulus if I remove the cut casings,” says Martial Burguieres, vice president subsea well services, Wild Well Control. “We do just the opposite. We actually leave the casing in place and place competent, tested cement plugs in those outer annuli.”
The approach utilizes multiple Wild Well Control technologies and techniques. The 7Series is a 7 3/8in nominal light well riserless intervention system that is placed on the subsea tree (vertical or horizontal). With a pressure control head and lubricator assembly attached to the system, riserless intervention is enabled. DeepRange, a fully US Bureau of Safety and Environmental Enforcement (BSEE) APM approved riserless P&A tool, is run in conjunction with the 7Series and allows perforating and circulating plugging material through an outer annulus, rather than perforating and squeezing. The concentric circulating system (CCS) is a pipe-in-pipe system that utilizes a 6 5/8in drill pipe and a 2 7/8in internal tubing to circulate material to and from the surface through flexible hoses between the CCS and the 7Series and the wellhead. The 6 5/8in drill pipe is also used as a landing string for the 7Series and the DeepRange (PA) tool. The Well Intervention Control System was developed in conjunction with input from Oceaneering and provides subsea electro/hydraulic controls.
To perform the P&A operation, the crew first performs a temporary well abandonment, cutting and pulling tubing. The crew then sets a cast-iron bridge plug (CIBP) in the production casing, via e-line, and sets a packer assembly several hundred feet above the plug. The 7Series intervention system then connects to the wellhead and the DeepRange tool is run through the 7Series. After the PA seal assembly is stung into the packer, creating the “A” annulus between the tool and the production casing, the upper isolation assembly is locked and the crew retrieves the DeepRange running tool.
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Prep to splash 7Series from Ensco 8505. |
The casing is perforated below the packer using e-line carried charges specifically developed to penetrate the casing size(s) in the well. The casing above the packer is then perforated using charges carried on the PA tool tubing string. Using the CCS, circulation is established through the DeepRange tool and below the packer through the “B” annulus, and the returns are taken back to the vessel/rig. With circulation established, cement (and/or resin) is pumped into the “B” annulus. After it hardens, the well is pressure tested as required by applicable BSEE regulations. Unlike the perforating and squeezing method, where the cement can go up or down the annulus, successful circulation tests allow the location of the cement to be known and multiple annuli can be perforated and isolated. To date, as many as three annuli have been perforated, cemented, and tested.
With the first cementing job done, e-line perforation into the “C” annulus below the packer is performed. Testing through the “B” annulus upper perforations then confirms isolation of the lower perforations into the “C” annulus, and the second set of charges on the DeepRange tool are activated to penetrate into the “C” annulus above the packer. Circulation is then established through the “C” annulus. The circulation process is repeated, the cement (and/or resin) is pumped and set, and the cement is pressure tested.
“We leave the uppermost annular plug in what we call a balance condition, which is essentially a solid cement column across the well,” Burguieres says. “This fully meets BSEE regulations for a plugged and abandoned well.”
To complete the well abandonment, the DeepRange system is retrieved, another CIBP is set above the upper perforations, and cement is dump-bailed or spotted on top as another mechanical seal.
The systems are currently being used on the eighth well of a nine-well campaign. In the first seven successfully abandoned wells, anywhere from 1-3 annuli were required to be plugged and tested. The last two wells each have two annuli to be plugged and tested.
The Wild Well Control, Marubeni, and rig operations teams overcame several new challenges on the first two wells: deploying the DeepRange tool, deploying the well control package below 7000ft, and using a new control system.
Wild Well Control will present on this topic at the 2016 Deepwater Intervention Forum this 9-11 August 2016, presented by OE. To view the full agenda and/or register, visit: www.deepwaterintervention.com.
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