formation | Energy Glossary

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1. n. []

The fundamental unit of lithostratigraphy. A body of rock that is sufficiently distinctive and continuous that it can be mapped. In stratigraphy, a formation is a body of strata of predominantly one type or combination of types; multiple formations form groups, and subdivisions of formations are members.

See: differential compactionformation pressuregeologic mapgeostatic pressureisochoreisopachlithostatic pressurepermeabilityrelative agestructure maptighttrapunderpressure

2. n. []

A surface land form.

See: geologic map

3. n. []

A general term for the rock around the borehole. In the context of formation evaluation, the term refers to the volume of rock seen by a measurement made in the borehole, as in a log or a well test. These measurements indicate the physical properties of this volume. Extrapolation of the properties beyond the measurement volume requires a geological model.