Sedco Rigs a blank slate

-- FROM THE FULL PICTURE MAGAZINE -- To meet market demands for deepwater drilling, Transocean chose to upgrade two of its Sedco 700 series drilling rigs to dynamically positioned class 2 semi-submersible rigs. The process was so comprehensive the rigs were classified as newbuilds.

Before Transocean's Sedco 706 set course for Brazil last year to drill for oil on a five-year contract with Chevron, she underwent a year of upgrades at the Keppel FELS Yard in Singapore. The aim was to retrofit her into a dynamically positioned (DP) class 2 semi-submersible rig, capable of operating in moderate environmental conditions and in water depths down to 6500ft. In order to achieve this, major structural works were carried out, including a pontoon and column extension in order to contain more drilling fluids. Mark Vermeulen, Commissioning Engineer at Transocean elaborates: "This upgrade included a completely new drilling system, a new piping system as well as new marine and ballast systems. When we started the rebuilding project, only the pontoons and columns were left. In order to keep the stability of the rig, extra blisters were added to the columns and the pontoons were extended to be able to deal with all the new equipment."

Keeping the value

As the world's largest offshore drilling contractor, Transocean leases floating, mobile drill rigs, as well as the equipment and personnel needed for operation, to oil and gas companies worldwide. The company launched its first jack-up drilling rig in 1954. Since then, Transocean has had a long history of ‘firsts': among them, the latest generation of ultra-deepwater semi-submersible rigs and drillships, of which the upgraded Sedco 700 rigs make up an important part.

"For Transocean, upgrading is a way of ensuring that our assets stay valuable and our fleet stays up to date. By adding new technology to ships, they become compatible with current applications and requirements," says Vermeulen. In addition to the cost saving, Vermeulen sees several advantages of refitting, compared to building completely new rigs.

"One advantage is saving time. Production time is reduced, meaning that you'll get a much faster return on investment for the conversion. A newbuild may give you new facilities that might not be possible with a refit, but it takes so much more time."

Safety first

Deepwater drilling takes place far from the coast in water depths of more than 4,500 ft. Semisubmersibles, such as Transocean's Sedco 700 series, are fitted with large, buoyant pontoon structures below the water surface and columns passing through the water surface supporting the platform deck at a significant height above the sea surface. Keeping the position of a semi-submersible rig during oil drilling and gas exploration is of critical importance for safety. In order to achieve this, the Sedco 706 semisubmersible rig relies heavily on its Dynamic Positioning (DP) system for automatic station keeping; it previously relied on anchors. As a result of the upgrade, Sedco 706 now features a DP class 2 system provided by Kongsberg Maritime. The upgrade also consisted of systems for power management, thruster control, vessel control & auxiliary as well as fire and gas with emergency shutdown from Kongsberg Maritime.

"The Kongsberg systems contribute to the safety of the people onboard and the management of the rigs," says Vermeulen. "We are now dealing with automated systems that monitor and provide supervisory control and operation, ensuring that we protect the environment, the people and the equipment onboard. Compared to where they were before the conversions, these rigs have made a huge step forward with regards to automated protection and control."

Like a football field

When winning a refit contract, Kongsberg Maritime usually sends an expert to perform a site survey and prepare a site report including a suggested system layout, a detailed project plan and a cost analysis. This forms the basis for the delivery contract, before the engineering phase, installation, commissioning and training. The refit of Sedco 706 however, was slightly different.

"I usually go onboard the vessels at the beginning of a project to perform a site survey, but in this case everything had been taken away, so there was nothing to see. Instead we made a detailed project plan with the site team from Transocean and adjusted the scope of supply," says project manager at Kongsberg Maritime, Håkon Hvidsten.

"When I went onboard the 706 for the first time, it looked like a football field on top. There was nothing there. It was so large that although there were close to 1400 people working onboard at peak time, I hardly saw a single person."

Double conversion

The retrofit of the Sedco 706 is the second in a double conversion contract. Transocean had already upgraded its Sedco 702, with mainly the same team from Kongsberg Maritime involved. The lessons learnt from this first conversion became the basis for the Sedco 706 project. "The original engineering was planned so that the two rigs would have an identical conversion, starting from the same position and basically ending in the same position. It was intended as a duplicate conversion one after the other, but they ended up with large differences. On the 706 we agreed to have only two main points of contact with Kongsberg Maritime, so that anything within our organisation related to the Kongsberg systems went through us. This narrowing down of the contact lines made a huge difference for the efficiency of the project," explains Vermeulen.

Local involvement

Another main difference between the two conversions was that with the 702, most of the work was done from Kongsberg's main office in Norway. During the conversion of the 706, a local team in Singapore took care of most of the same work. This is the first time a refit project has been run entirely from this local Kongsberg Maritime office.

"We have a large office in Singapore", says Hvidsten. "In general, the 702 was run by Norwegian engineers with assistance from the local office. At that time, the Singaporean office was still undergoing extensive training to reach the level they needed to be at, so when 706 came along, they were more than prepared to run the project."

This local involvement was a result of a specific request from Transocean in order to minimise the travelling time and expenses of the engineers if support was needed, and to ensure local competence for future projects. "For each engineer in the project, there is cost involved. We wanted the flexibility to increase the work force if required. This would be easier and less expensive from the local office. By increasing skills locally, you also increase the possibility that they can take care of future projects without always relying on heavy support from Norway. I think that this turned out to be a benefit for everybody because it has been driving local employees to reach the level that you want to see for your branch offices," Vermeulen says, also emphasising local involvement as an advantage in the training of staff.

"A lot of our staff members need training and if there is a local, regional office it reduces our travelling costs in connection with courses."

A better company

Hvidsten describes the benefit of these refit projects to Kongsberg Maritime: "This is an extensive contract comprising many of our products, including automation, DP and safety systems. Transocean is an important customer and it's always interesting to work with the leading companies within their field. You always know they have high technological demands pushing our project group to perform better. Working in these types of projects contributes to making us a better company."

Kongsberg Maritime equipment on Sedco 706

  • Dynamic Position (DP) system including 3 operator stations, DP logger, multiple DP reference system and DP controllers
  • Power Management System including a history station providing facilities for long-term storage of alarms, events and time-series
  • Thrusters Control System
  • SVC (Vessel Control) & Auxiliary System including 12 SVC operator stations
  • Fire and Gas with Emergency Shutdown System (ESD) including multiple ESD matrix panels

A history of firsts

Transocean holds 80 per cent of the past 23 deepwater drilling records:

  • First offshore jackup drilling rig
  • First self-propelled jackup
  • First turret-moored drillship
  • First dynamically positioned drillship for exploration
  • First dynamically positioned semisubmersible •first fourth-generation semisubmersible
  • First rig to drill year-round in the North Sea
  • First semisubmersible for sub-Arctic, yearround operations in the Barents Sea
  • First semisubmersible for year-round drilling West of the Shetland Islands in more than 4,000 feet of water
  • First deepwater semisubmersibles with patented Tri-Act derrick
  • First ultra-deepwater drillship

Transocean today

  • More than 21,000 employees in 30 countries
  • Largest offshore driller with 138 mobile offshore drilling units, plus an additional eight newbuild rigs
  • Largest jackup rig driller with 65 units
  • Largest "floating" rig driller with 70 drillships and semisubmersible rigs
  • Largest deepwater driller with 36 rigs that can operate in water depths of 4,500 feet or greater
  • Largest offshore driller by equity market capitalization