Directional Holes 2 : Boreholes purposely drilled in a planned trajectory other than vertical; boreholes drilled using controlled directional drilling methods. (Bul D20)
The Mudblogger (Oilfield, Energy and Related Photographs), Oil Field Glossary, TX, USA 2014. http://mudblogger.com/oilfield-glossary/, (Oil - Amer) {777}