Glossary

Hole orientation

Borehole orientation follows a convention of deviation/deviation azimuth. For example, 5°/135° indicates 5° deviation from vertical towards 135° (south east). Hole orientation is usually detailed in degrees (very rarely in radians) as hole deviation and hole azimuth (or drift) each of which have a range of different mnemonics dependent on individual service companies. It is important to know which North (magnetic, geographical or grid) is being referenced in any survey. Note that hole orientation is measured from the vertical unlike the attitude of geological features that are recorded from the horizontal.

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About the glossary
This listing is not exhaustive or definitive, do not expect Oxford English Dictionary standards; it is aimed at those who need to understand basic principles and those that read reports on dipmeters and borehole images requiring some technical help to get the most from such documents.

We have attempted to make the descriptions and explanations generic, giving the glossary a wide application and appeal, with minimal, if any, commercial bias. If you spot any mistakes, omissions or any problems with the explanations, please do not hesitate to contact us, and we will try to accommodate your comments.

Acknowledgements
This listing has been derived by Task Geoscientists. All external sources are fully acknowledged.