Page 64: of Offshore Engineer Magazine (Nov/Dec 2013)

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then be tripped to bottom on drill pipe to retrieve the tubing after the IRS was recovered.

The open water-portion of the P&A can been done in many different ways, with different approaches to testing casing annuli. The most common method is utilizing the easy drill subsurface valve (EZSV) and a tubing-conveyed perforated (TCP) gun to allow access to the annuli. This method is performed by tripping the

EZSV and TCP guns to depth and setting the EZSV. Once

EZSV is pressure tested from below to confrm it was properly set, the TCP guns will be fred, perforating the production casing. Pressure is monitored and recorded during fring. Any existing pressure will be bled off and monitored again.

An injection test is then conducted at a pressure greater than leak-off test pressure to check the integrity of the annulus. If injection is possible, a squeeze-cement job will be performed on the annulus. If injection is impossible, then a negative test is performed to confrm integrity. The string is then retrieved from the retainer.

Once integrity of the squeeze is confrmed by both the pressure test and the negative test, a cement plug is set above the EZSV. The process would be repeated for the intermediate casing to 20in annuli perforating through two sets of casing with TCP guns.

Another option is to cut the production casing and recover to surface once annulus integrity is confrmed between production and intermediate casing, allowing for a mechanical barrier to be set in the intermediate casing. If this option is elected to be performed, the TCP gun would only be required to perforate the intermedi- ate casing to ensure integrity rather than perforating two sets of casing to access the intermediate to 20in annuli. Once complete, a surface plug would be set.

The surface plug is weight tested, utilizing drill pipe to

Open decks and sizable cranes aboard the vessel provide more effcient tag the top of the plug and set down weight to confrm mobilization.

Photo: Helix ESG the plug has integrity. prepare for the second balanced plug to be circulated Upon completion of the surface cement plug, an ROV into place with coil tubing. will set a debris cap on the wellhead, completing the

Once the second balanced cement plug is set and well work. The vessel will then perform a fnal survey successfully pressure tested, electric line is directed with the ROV and complete demobilization from the

OE REVIEW into the well with a tubing cutter. The production tubing well site. would be cut above the balanced plug to allow for the recovery of production tubing. Prior to unlatching, a Darin Hilton has been Helix’s negative test is performed with sea water and then well commercial manager for Well circulated to ensure kill weight fuid on both production Operations in the US since 2012, and annulus sides in the well. and has worked for Helix Energy

Solutions Group for more than

OPEN WATER AND SETTING THE PLUG fve years. He has more than 18

Prior to pulling the trees during the riser-based por- years of experience in the offshore tion of the P&A, ROVs fush and remove any fow line industry. Early in his career, jumpers by pre-rigging them with slings and cutting Darin worked at Marine Trans- the jumper into manageable sections for the subsea port Lines. Darin also worked at BP as a marine su- crane to recover concurrently to the P&A work. This pervisor with and a superintendent for three produc- eliminates the need for a construction ROV vessel to ing felds. perform any pre-work prior to arrival on location of At Helix, he has served in three roles, including a the P&A vessel. three-year stint as Master/ OIM on the Q4000 during

Once tubing is clear of the well the vessel will move the oil spill response at Macondo. to a safe zone to fnish recovery. If the well was designed Darin holds a BS in Nautical Science with a mi- with a vertical tree, the IRS would be recovered through nor in Marine Engineering from Maine Maritime the riser and the tree would be concurrently recovered Academy. Darin also has a USCG Master Unlimited by the subsea crane. A tubing hanger running tool would Tonnage license with OIM-unrestricted endorsement.

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