1. n. [Formation Evaluation]

The adjustments that must be made to log measurements to bring them back to the standard conditions for which the tool has been characterized. Different measurements require different corrections. For example resistivity measurements usually require correction for the borehole, invasion and shoulder beds, and may also be corrected for apparent dip, anisotropy and surrounding beds in horizontal wells. Density measurements require correction only for borehole size, while neutron porosity measurements require corrections for temperature, pressure and a large number of borehole and formation parameters. Not all corrections are significant in all cases. Corrections can be calculated manually, using charts, or applied through software. Conventionally, corrections are applied sequentially, as for example first borehole then invasion. In some situations, such as the combination of deep invasion and high apparent dip on a resistivity measurement, the corrections are too interdependent for sequential application to be accurate. The solution is iterative forward modeling.

See: apparent dip,  borehole correction,  iterative forward modeling,  neutron porosity,  shoulder bed,  step profile