Control Cylinders : Hypothetical limits in the form of a cylinder around the planned trajectory of the wellbore and in which the borehole is to be maintained. (Bul D20)
The Mudblogger (Oilfield, Energy and Related Photographs), Oil Field Glossary, TX, USA 2014. http://mudblogger.com/oilfield-glossary/, (Oil - Amer) {777}