Angle between a scribe line on a tool relative to either the high side of the well or magnetic north. Gravity tool face is the angle between a tool reference axis and gravity in a vertical plane, used when the hole is inclined greater than approximately
Angle between a scribe line on a tool relative to either the high side of the well or magnetic north. Gravity tool face is the angle between a tool reference axis and gravity in a vertical plane, used when the hole is inclined greater than approximately 8º. Magnetic tool face is the angle between the tool reference axis and magnetic north in a horizontal plane, used when the hole is inclined less than approximately 8º.
LUTHI, S. M. 2000. Geological Well Logs. Springer, Berlin, p373.
THEYS, P. 1999. Log Data Acquisition and Quality Control, Second Edition. Éditions Technip, Paris, p 453.