In the operation of a compressor system in a subsea station for transporting a well stream, separated well stream gas is supplied to a compressor (12, 13) which is arranged with its motor (8) in a common drive atmosphere within a pressure shell (21). As the drive atmosphere there is used a suitable, continually supplied dry extraneous gas, which is supplied to the well stream. There may be used a suitable dry extraneous gas which is stored in liquid form in an insulated container. There is also described a compressor system wherein there may be used as the drive atmosphere a continuously supplied, suitable dry extraneous gas.