With gas and oil reserves becoming increasingly scarce there is considerable emphasis on new technology aimed at maximising yield from wells. Amongst the companies endeavouring to satisfy this demand is the UK-based company Corac Group plc who are developing their ‘Downhole Gas Compressor’ technology.

The object of Corac’s new compressor technology is to boost gas output from brownfield sites by as much 30-50% from otherwise un-economic wells. Indeed, the Downhole Gas Compressor could be used to make otherwise non-commercial projects viable propositions. It can be introduced into a well at any time and can even be employed in wet wells.

During development and proving trials of the compressor, Corac carries out above-ground testing in their gas well ‘flow loop’ simulator. This calls for an effectively controlled power supply to the compressor.

A raw 3Ø supply is fed to a REO AC power supply unit which converts it to a variable 3Ø AC supply. This is then fed to a rectifier which converts the AC to DC (0-2500V). The variable DC voltage connects to an inverter that drives a motor in the compressor which, in turn, rotates an impeller at high speed to develop a pressure ratio across the compressor.

In this power system, the REO power supply is commanded by a control computer via its RS232 serial communication interface. It is via this RS232 port that Corac engineers can send control data that governs the speed of the motor driving the compressor.

According to Corac , the integral RS232 of REO’s AC power supply has provided a simple yet effective way for the Downhole Compressor’s supervisory system to achieve and maintain motor speed and, hence, the pressure developed by the compressor.