Profile: Northwestern Air Service specializes in providing air/under balanced drilling equipment and services. our products include mist pumps, combo compressors & boosters and dog hose pipe racks. Our services include underbalanced drilling, air/mist/foam drilling, aerated or nitrified fluids, pipeline commissioning, nitrogen flooding and trucking services. Underbalanced drilling services is the drilling of a well with a circulation medium which has an effective pressure gradient which is less than that of the formation pressure of the section to be drilled. The main benefits of drilling underbalanced is to minimize formation damage and increase penetration rates and. During conventional drilling there is a positive differential pressure in that the drilling fluids pressure is greater than the formation pressure and the drilling fluids will flow into the formation. In conventional drilling a filter cake is formed (hopefully) and acts as a protective barrier, reducing damage to formation permeability from drill cuttings.