Redevelopment In The North Sea 

This article originally appeared in the July issue of CompressorTech2. We only publish a fraction of our magazine content online, so for more great content, get every issue in your inbox/mailbox and access to our digital archives with a free subscription.

BY ROBERTA PRANDI 

Baker Hughes (BHGE), a GE company, has been chosen by Maersk Oil (now Total) for the supply of turbomachinery to the topside production facility of the Tyra field in the Danish North Sea, that is being redeveloped.  

Riccardo Barbieri, executive sales director Europe at BHGE’s Turbomachinery & Process Solutions, directly followed this project since its beginning and pointed out to COMPRESSORtech2 the importance of the Tyra field as hub for gas production directed towards Denmark.  

The fixed platform of the Tyra field that is being redeveloped had significant problems with sinking. The operator decided to opt for a solution involving the cutting off of the platform’s deck and the replacement with a new, higher one; at the same time looking at an increase in the gas production too. 

Barbieri, 25 years spent with GE Oil & Gas – now BHGE – and since 15 years working from the company’s headquarters in London, UK, said that BHGE will supply the turbomachinery technology for the gas compression side and for power generation services related to the platform’s utilities and the gas dispatch. The equipment will be manufactured, packaged, and tested in the BHGE Turbomachinery and Process Solutions (TPS) centers of Florence, Italy, and Le Creusot, France. 

Three BHGE’s aeroderivative LM2500 gas turbines will be utilized for power generation, with two units in operation and one in stand-by. Each unit has a power output of 33 MW and is particularly suited to fixed offshore platforms for its compact package, reduced weight, and simplified maintenance that can be carried out within a day.  

On the compressors’ side, BHGE’s solution consists of seven compressor trains with 16-MW variable high-speed electric motors by GE Power directly coupled with BCL centrifugal compressors, with both driver and driven machine using active magnetic bearings (AMB). This non-integrated configuration derives from BHGE’s Integrated Compressor Line (ICL) technology, that has been employed for years (currently 36 compressors in the field). 

“The compressor solution with AMB technology is quite interesting from a footprint and weight point of view, as well as for maintenance,” said Barbieri. “One of the key requirements from Tyra’s operator – and one of the main challenges for the project – was a reduction in weight and size, so that we concentrated on a solution which could comply with both. GE Power’s variable high-speed drive systems (VSDS) are a proven technology with interesting possibilities for optimizing the compressor/driver package. 

“On the other hand AMB technology, that BHGE proposes in collaboration with bearing specialist SKF, allows to move away from solutions with a gearbox and conventional oil lubrication systems, to an oil-free system. This contributes to weight and volume reduction, while having a significant benefit with maintenance operations by avoiding even those minor inspections necessary with oil-lubricated bearings.” 

BHGE’s pilot project for this compressor technology was Total’s Martin Linge field (now Statoil) on the Norwegian continental shelf, which is currently in the commissioning phase. 

According to Barbieri, ICL is still not much in use with offshore applications, while it is quite popular for pipelines and gas storage stations. “We think that this oil-free technology though has a remarkable appeal for offshore facilites, mainly thanks to its fully leak-free status in the environment.” 

Instead of a combustion engine, ICL has a high-speed electric motor fully integrated with the compressor in a single sealed casing. The high speed electric motor is connected to a variable frequency drive to regulate its speed. The rotor is levitated by AMBs and a precision control system. AMBs offer higher reliability and availability, with 40% lower requested maintenance than a conventional compressor. 

The ICL design is simple and approximately half the size of a conventional compressor. ICL units have a much wider operating range than conventional compressors: 35-105% of nominal speed versus the typical 70-105%.