1. n. [Formation Evaluation]
The effect on a laterolog whereby the current lines are no longer properly focused but spread out at a certain distance into the formation. The effect occurs opposite a high-resistivity bed with low-resistivity shoulders. The result is that laterolog devices, in particular deep devices, tend to read too low and have less depth of investigation. Shoulder bed correction charts correct for these effects in certain well-defined situations, such as no invasion in horizontal beds with vertical wells.