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Corac in-pipe compressors able to double production

Hydrocarbon Engineering,

UK gas, air and energy technologies group Corac has a brand of centrifugal compressors which use a rotating bladed impeller to accelerate gas to a high speed, which then slows down through a diffuser to exit the machine at higher pressure than it entered. The company’s patented compressor technology has shown that in some applications, it could double the overall production of gas from a well.

Compressor technology

Corac Energy Technologies (CET) has developed this patented compressor technology. They use highly efficient permanent magnet motors and patented gas film bearings to provide frictionless support to the single rotating part. Tests in industrial settings have logged the shaft spinning for more than 27 000 hours at up to 72 000 rpm. At this speed, the blade tip is travelling at more than 500 m/sec (one and a half times the speed of sound, and at more than 2000 km/hr, almost as fast as the top speed of a Eurofighter Typhoon).

Engineers at CET first tackled the problem of size by producing an impeller one third smaller, and streamlining it further by removing the external cooling for the motor so that the gas itself became the coolant. The result is a compressor that is 12 cm wide and 70 cm long. It fits completely inside a seven-inch casing and was demonstrated in Texas last year in a live gas well. It has experienced more extensive testing since in CET’s UK facilities.

In these tests, the compressor has consistently produced a pressure ratio greater than 1.2 to 1 at an actual flow rate of approximately 20 000 m3 per day.

Energy applications

At these performance levels, CET has been working with energy companies to find the most valuable uses, and suitable configurations for this technology. One such case is to support the production of high performing wells where there are local variations in reservoir pressure. Prolific wells will deplete the local gas quickly, and then stop producing. After a period they can start up again at high productivity. A relatively small reduction in wellhead pressure, for example by 50 or 100 psi on a line pressure of 1000 psi can substantially boost production in the short term and keep the well flowing at high rates for longer.

Current calculations show that use of CET’s patented in-pipe compression technology could double the overall production of this type of well over a period of many months. In high performing wells, this is a really valuable result. Tests and calculations are continuing as CET and its partners define the best uses for this technology. Results are encouraging, as the alternative is to reduce pressure across the whole field using massive and very expensive central compression installations.


Dr Adrian Alford, Chief Technologist at Corac Energy Technologies, commented: “The CET technology is designed to focus compression where it is most needed. We aim to put our specialised compressors into the heart of bigger systems in a modular and flexible package. Small and localised responses to compression requirements have found uses well beyond our original intent, and more work this year will show just how far this technology can go.”

Adapted from press release by Katie Woodward

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