A shear success

Shell needed a non invasive technique to measure process levels on its flagship Shearwater platform. Nucleonic devices proved rugged enough for these extreme conditions

The Shearwater offshore development lies 207km east of Aberdeen in the North Sea. This large offshore project incorporates wells that sink three miles below the platform into the Shearwater reservoir.

Shearwater is operated by Shell UK Exploration and Production in the UK sector of the North Sea for Shell, Esso and other co-venturers. It began operation in August of this year and for this millennial venture, Shell wanted to move away from the conventional approach in a bid to make the launch of Shearwater a more open and associative process. It was in this spirit that engineers working on Shearwater approached Endress + Hauser for measurement solutions on a variety of vessels on the flagship platform.

Endress + Hauser’s FMG671 Gamma transmitters were chosen to measure the level of the process fluids, as these instruments are non-invasive, highly durable and provide extremely reliable results.

The applications used on the platform involved temperatures as low as -80ºC and mid-range pressures (+100 bar) on vessels including the low temperature separator, turbo-expander suction scrubber and the cold condensate flash drum, including the flare KO drum. By using nuclear technology, unnecessary welding and fabrication of the vessel structures was avoided. The radiometric source is mounted outside, on one side of the vessel, with the most sensitive Gamma sensor in the world mounted on the opposite side.

The Gamma source, in this case a caesium 137 isotope, emits radiation which is reduced as it passes through materials. The actual measuring principle is based on the absorption of radiation by the product to be measured. Due to changes in absorption when used for measuring density, interface or level of the product, a fraction of the original radiation still reaches the detector even at maximum attenuation.