1. n. [Formation Evaluation]

A borehole that is not to gauge or is rugose. The term usually refers to the detrimental effect that such a borehole has on the response of logging measurements, in particular pad tools like the density or microresistivity. The existence of bad hole is usually determined by a caliper log and on various secondary measurements such as delta rho.

See related terms: cave effect,  corkscrew hole,  rugosity