Glossary
Borehole sampling bias
Boreholes drilled perpendicular to a set of geological features will readily intersect these features on images or dipmeters. In strong contrast, those wells drilled parallel or near parallel to a set of geological features will rarely intersect such features. This results in borehole sampling bias, with feature recognition a function of hole orientation rather than the spatial organisation of such features. This will result in an under determination of features (e.g. fractures), and other surfaces, that strike parallel or near parallel with the borehole azimuth. This sampling bias can also include bedding planes, in particular with steeply inclined or horizontal wells. Borehole bias can be severe with many important surfaces not incorporated into interpretations. A partial correction for this borehole bias can be made which helps limit its effect.
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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.