IMRs: A better mousetrap for underwater work

DMT Emerald carries a DeepWorker 2000 manned subersible for undersea construction and repair work.

With oil prices reaching new heights this year, it is more important than ever to squeeze every drop of oil possible from existing wells and to install new wells in deep water. That has given rise to a new class of vessels in the Gulf. Called IMRs — inspection, maintenance and repair — these boats are configured for work on the wellhead or other subsea infrastructure transporting oil and/or gas.

IMRs such as Chloe Candies, Harvey Discovery and DMT Emerald are recent boats of this type that are working in the Gulf of Mexico. Under construction are Grant Candies and Ross Candies.

Unlike their supply-boat brethren, these vessels carry neither drilling mud, fuel oil or other liquids in belowdeck tanks, nor cargo on rear decks for transfer to rigs or platforms. Their duties normally involve new construction or repair projects to enhance hydrocarbon flow.

This type of vessel is becoming increasingly valuable in deepwater projects because of its ability to do many tasks well without the substantial cost of using a semisubmersible rig for the same purpose.

Grant Candies and Ross Candies are being built by Dakota Creek Industries, Anacortes, Wash., for delivery in late 2008 and 2009 respectively. Chloe Candies was a 2007 delivery and was one of the first vessels delivered from the Otto Candies LLC shipyard in Houma, La. Formerly Houma Fabricators, the yard has several projects underway for Otto Candies LLC, the Des Allemands, La.-based offshore oil/gas service company.

Chloe Candies was leased to Saipem America and joins Harvey Discovery, HOS Innovator and other vessels in the Saipem America fleet specifically designed for offshore construction and repair projects.

While the three Candies vessels are not sister ships, they are remarkably similar in specifications. Grant Candies is 292-foot vessel with a 59-foot beam and a 24-foot molded depth with Class 2 DP, a 8,866-square-foot deck, a 25-foot-by-20-foot moon pool and active heave compensation to assist with the deployment of large heavy seabed infrastructure.

A 100-ton stern roller and a 100-ton Teleknuckle crane are used for over-boarding large structures and equipment unable to utilize the moon pool. Manifolds, jumpers, umbilicals, coiled tubing and flow lines are examples of equipment that need to use the crane and stern roller for deployment. The slightly larger Ross Candies will have a 150-ton crane.

Like many vessels of this type, Grant Candies uses a diesel electric power plant consisting of two Caterpillar 3512C diesels driving 1700-kilowatt generators and two Caterpillar 3516C engines powering 2250-kilowatt generators. This electrical power is used to run a pair of Schottel 2250-kilowatt stern thrusters (Z-drives) and two 1,000-kilowatt bow thrusters also by Schottel, plus ship’s power.

Trial speed of the vessel was 12 knots, design draft is 5.0 meters and deadweight is 3,700 tons.

Grant Candies is set up for major below-sea infrastructure work. The 100-ton single drum below the main deck deep-sea winch is located over the moon pool with a 100-ton deck mast. There are a pair of 200-hp Innovator ROVs with the ability to handle a variety of support tools that further expand the capabilities of Grant Candies.

There are accommodations for 86 persons in one-, two- and four-person cabins.

Grant Candies is classed by the American Bureau of Shipping (ABS) A1 (E) Offshore Support Vessel, AMS, ACCU and DP-2. The vessel is also U.S.-flagged and full Ocean SOLAS.

Deep Marine Technologies (DMT), Houston, is a rapidly growing company that was named in Entrepreneur magazine as one of its Top 10 of the magazine’s Hot 500 firms.

Its specialty is working on subsea projects and it has built and purchased several vessels to carry out this mission.

In the past two years it has purchased three supply vessels from Otto Candies LLC. “We did the conversion work on all three vessels in our shipyard, Otto Candies Shipbuilding in Houma, La.,” said Brett Candies, traffic manager and vice president of Otto Candies LLC. These include Kelly Ann Candies, a 240-foot vessel now called DMT Sapphire, that will be used as an ROV support vessel and the 240-foot DMT Diamond, formerly Nicki Candies, will do construction support work. The 220-foot Agnes Candies, now DMT Topaz, has been equipped with a 40-ton knuckle boom crane, a 12-man saturation system for divers and a gas mixing system, to support a dive team as well as a diver-reclaim system.

DMT has also had Bender Shipbuilding and Repair Co., of Mobile, Ala., build a new 292-foot vessel, DMT Emerald, with capabilities to carry out a range of subsea construction and repair work.

DMT Emerald is powered by four Caterpillar 3516B engines coupled to 1,825-kilowatt Caterpillar gensets. A pair of Steerprop azimuthing Z-drives rated at 1,600 kilowatts each and two 1,000-hp Berg tunnel bow thrusters furnish propulsion power.

One of the outstanding features of this vessel is a 100-ton heave compensated lifting tower placed over the vessel’s 23-foot-by-25-foot moon pool to facilitate the installation and retrieval of subsea infrastructure. For over-the-side retrieval and placement of subsea construction assets, DMT Emerald mounts a Hydromarine 100-ton knuckle boom crane.

Two Triton 150-hp work-class ROVs by Perry Slingsby Systems, of Jupiter, Fla., are on board with 10,000-foot depth capacity. The vessel also carries the Deepworker 2000, a one-atmosphere submersible that can carry a diver to 1,800 feet deep and is outfitted with digital acoustic telemetry modems to transmit live images and data to DMT Emerald. The Deepworker 2000 is equipped with an onboard hydraulic-powered, multifunction manipulator and grabber.

A recent example of the type of work done by DMT Emerald is a project at the Blind Faith development in Mississippi Canyon operated by Chevron. Working for Aker Marine Contractors in 6,500 feet of water, the vessel was involved in tying in two 14-inch risers, one 6-inch riser and one 8-inch riser. In addition to the vessel-mounted ROV, surface divers were used.

The vessel offers accommodations for 73, has a helicopter landing deck rated up to a Sikorsky S76 helicopter and has a three-bed hospital.

“We believe the purchase of these new assets and plans for continued expansion of our fleet underscores the level of DMT’s commitment to the Gulf of Mexico and the oil and gas industry,” said Chief Executive Paul McKim.

By Professional Mariner Staff