Glossary

Drilling-induced tension fractures

Includes tension fractures, induced fractures & hydraulic fractures.

The drilling of a borehole leads to a change in the local in-situ rock stress state in the vicinity of the well bore. For a vertical hole drilled parallel with a principal stress axis a stress reduction occurs in the area of the borehole in the direction of maximum horizontal stress (Shmax). Tensional failure can occur where tangential stresses are lowest, in the direction of Shmax, with the formation of drilling induced tension fractures (DITFs). They are usually recognized on image logs as two twinned vertical, or near vertical, irregular and discontinuous fractures set 180º apart that often terminate at lithological boundaries. The use of DITFs is a recognised method for determining in-situ stress direction within boreholes.

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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.