Removing obsolete oil rigs

Once a rig stops producing economic quantities of oil, the site is usually abandoned. To restore the “landscape” of the North Sea, the oil rigs need to be removed as soon as possible after abandonment.

Oil rig being removed with floatation tanks in place
Oil rig being removed with floatation tanks in place

Offshore surveying

Surveying an oil platform in the North Sea
An engineer surveys a platform in the North Sea

The Norwegian offshore surveying company iSURVEY supports oil rig operations and deep water construction work. They provide all services related to offshore surveying, positioning, calibrations, mapping, GIS and geodetic consulting. They manage their own suite of applications for different tasks and have during the past decade grown to become a major player in the sector.

On the hardware side, iSURVEY rely on Topcon for a significant number of GNSS receivers, antennas and robotic total stations. Blinken AS, Topcon's Norwegian dealer, delivers and supports the equipment. The instruments are well integrated with iSURVEY's own software. All equipment is accessible via wireless remote control which is essential, as most installations that are being monitored and positioned may be unmanned due to safety restrictions.

Obsolete rigs

A floatation device is used to support an obsolet
A floatation device is used to support a rig

One major assignment has been the removal of an obsolete rig from the North Sea. Four 70m tall floatation tanks were positioned and manoeuvred remotely to jack up the remains of an old platform with a mass of approximately 16,000 tonnes. Each tank had not one, but three rovers receiving RTK corrections from three reference stations on the platform, adding up to 15 receivers working simultaneously offshore for several days surrounded by steel generating difficult multipath conditions.

The first phase involved manoeuvring the tanks to dock onto the platform with a tolerance of 20cm at open sea. The second phase was positioning the platform during tow. Roger Gildseth, iSURVEY Technical Director, said the real time positioning went so smoothly his engineers joked that the whole operation could have been done with the "curtains closed" and just watching movements and positions on the remote screens.

Quicker than the waves

For other projects like docking onto or jacking up platforms, and moving operational rigs, iSURVEY utilises robotic total stations. The rapid wave movements give the QS total stations the opportunity to stand out. The instrument's outstanding auto-tracking capabilities ensure fast secure data feeding to iSURVEY software displaying instant information to the operators.

Only by precise remote positioning it is possible to monitor movements and control platform activity, allowing for entire removal of an obsolete rig from its current position to restore the location to its natural state.

Interested in seeing your project featured?

Do you or your company have a project you'd like to share with civil engineers from across the globe?

Our Knowledge Marketing team sources content from across the world of civil engineering, as well of as offering opportunities for sponsorship.

Training opportunities from ICE

ICE provides world class training for civil engineers looking to develop their skill set.