1. n. [Formation Evaluation]
The response of a logging measurement as a function of distance parallel to the tool axis. The word vertical implies a vertical well, but the term is used at other wellbore deviations. Vertical responses are determined by computer simulation or laboratory measurement. For some measurements, mainly resistivity, the vertical response can be shaped as desired through signal processing. In general, the vertical response depends on the formation properties throughout the measurement volume. Most quoted vertical responses have been determined in formations that are radially homogeneous and have small vertical changes. They can then be summarized by a geometrical factor or a pseudogeometrical factor. These factors are appropriate for volumetric measurements such as nuclear and resistivity, but not for others such as acoustic propagation.