Over 200km (130 miles) off the south-east coast of Louisiana, USA, a helicopter touches down on a helipad on the bow of a ship. Its passengers trade places with a team of workers waiting close by. This is changeover time for the crew of Bully I, a drillship working on the Mars B deep-water project in the Gulf of Mexico.

Shrinking to drill deeper

Traditionally the extra equipment, pipes and well lining needed to reach deep-water oil and gas resources at greater depths pushed up the size of drillships. Bigger ships require more fuel.

But Dave Loeb, Shell Wells Operations Manager, wanted a more economic solution. In 2005, Shell and offshore drilling contractor Noble Corporation worked on a new design that eliminates surplus space and carries only essential equipment. The result is the Bully.

Around 160 crew members rotate on 21-day shifts to manage operations on board Bully I. The ship is designed for deep-water operations and can drill in water depths up to 2,500 metres (8,500 feet).

Two sister ships were built. Bully I has drilled wells at the Mars B project in the Gulf of Mexico, while Bully II is helping expand the Parque das Conchas project off Brazil.

“The Bully is dwarfed by some of the larger drillships,” says Dave. “But it still does a very good job.”

On-board crew facilities resemble those of a hotel, with a gym, cinema and quality catering that even includes a pastry chef.

The Bully needs a base onshore to replenish supplies and equipment more often. In more remote locations, larger drillships are still used.

The Bully compared to a conventional drillship

  • Around 2.5 metres (eight feet) narrower.
  • Up to 80 metres (260 feet) shorter.
  • Thrusters that keep the ship’s position combined with a smaller hull and electronic engine controls help improve fuel economy. It uses up to 26,000 litres (7,000 fewer gallons) of fuel a day on average compared to other deep water drillships.
  • A compact, box-type drilling tower takes up less space than a conventional drill tower design and contains all hoisting equipment inside, keeping people safer.
  • The drill tower is equipped with hoists that allow the crew to drill on one side while conducting other drilling-related operations on the other.
  • Automated technology replaces a lot of manual work, lowering costs and increasing on-board safety.
  • Can operate in water as shallow as 45 metres (150 feet) with the correct mooring.
  • It can drill down to 12,000 metres (40,000 feet).

With a desire to take the new generation of drillships still further, drilling-tower design firm Huisman took another approach.

“For the new drillship we first designed the drilling package then designed the vessel around it,” says Olaf van der Meij, Huisman Senior Concept Engineer.

On conventional drillships, the drilling and well-lining operations take place within the derrick structure. The new design places the drilling and well-lining equipment outside the tower structure. Thanks to the hoists on either side of the tower, the two processes can happen simultaneously. This boosts productivity and improves safety.

In addition, the drilling floor can be hoisted up to deploy the blow-out preventer, a mechanical device designed to rapidly seal off the well if control is lost. Without the need for a raised drill floor, the ship’s centre of gravity is lowered for greater stability.

Shell and Noble commissioned two of these new vessels in 2012 and 2013. The Globetrotter has been drilling for Shell in the Gulf of Mexico since 2012.

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