Page 90: of Offshore Engineer Magazine (Sep/Oct 2013)

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Bobby Lott, VP Well Services for

DSV Joanne Morrison

CMC, noted that they had recently com-

The has four-point mooring system for stability, a saturation- Joanne Morrison pleted a P&A operation for a McMoran diving system that can support four divers to 1000ft water depth (deployed well in the Gulf of Mexico where three through the moon-pool), and can do subsea inspection with a work-class ROV.

Subsea strings were cut and pulled: 9 5/8in., 13

Length 240ft 3/8in., and 16in.-diameter. The deep- est cut was 25ft below the mud line.

Width 48ft

With that length of cut tubular, he says

Molded depth 14ft that it usually requires pulling 40,000-

Main deck area 46 x 125ft 50,000lb more than the pipe weight to

Open deck space 5750sq ft extract the tubular.

Main deck cargo capacity225tons

Lott noted that the tool will not work

Fuel 60,000gal for every well, especially those with a

Water 90,000gal longer reach or with multiple grout-

Flag USA ings. But, most subsea wells are com-

Classifcation USCG/ABS pleted with mudline hanger systems

Crane Mantis Model 14010, 70-ton hydraulic set 100ft below the mudline, so most

Engines 2 x 645 EMDs C Model casing strings are not grouted together.

This makes the cutting task simpler.

Horsepower 1,500

For caissons that are driven over sur-

Main generators 2x 300 kW face casing (usually 30in.-diameter) to

Emergency generator 375 kW support a single well platform, CMC

Saturation generator 275 kW has added a feature to the tool that can

Winches 2 x SMATCO double-drum extend the cutting head out from well

Wire 4 x 6,000ft x 1-1/4in. center to cut 2.5in.-thick x 60in.-diam-

Dynamic positioning White Gill thrusters eter caissons.

Anchors 2 x 17,000lbs; 2 x 15,000lbs

Most P&A operations can be com- 4-man, saturation diving system (1000ft),

Diving system pleted in one day, according to Lott, moon-pool deployed saving signifcant time and expense

Hyperbaric rescue chamber4-man using the Joanne Morrison, CMC’s div-

Diving station deep air/gas surface ing support vessel. the required subsurface cutoff depth work. Using this new cutting tool,

FURTHER READING (15-25ft in the Gulf of Mexico), and they completed four wells for us at then it executes the cut using high about half of the expected cost. Chet pressure water with entrained abrasive, Morrison saved ERT and partners Further reading on decommissioning: a fnely-ground coal slag. many millions of dollars.” OE, August 2013, pg. 26.

Cutting effciency is limited by the hydrostatic head that the jetting tool must overcome. The tool is designed to compensate for pressures down to 1000ft water depth and CMC says it can cut through 3in.-thick material as well as multiple pipe strings.

The tool and resulting cut is con- trolled from the surface vessel. Once the stub is cut, the tool is removed and the freed stub can be extracted from the seabed and the open hole flled.

Energy Resource Technology GOM,

Inc. (ERT), former oil and gas sub- sidiary of Helix ERG, tested the tool at three felds in the Gulf of Mexico.

According to Rod Hebert, ERT con- sultant, “The [crew] did outstanding

The SHARC cutting head is secured in a frame that attaches to the exposed tubular.

OE | September 2013 92 000_OE0913_subsea1_SHARC.indd 92 8/18/13 8:41 PM

Offshore Engineer