Logging tool

Abstract

The present invention relates to a logging tool for logging formational changes in a borehole, the logging tool having a longitudinal axis. The logging tool comprises a radiating source (5) for emitting an interaction signal, a detector (6) for detecting a reaction signal, and a screen (7) for limiting a volume (53) investigated by the radiating source and the detector, wherein the tool comprises a first part (8) and a second part (9), the second part being able to rotate around the longitudinal axis relative to the first part during use, and the second part comprising the screen (7), and wherein a speed of rotation of the second part is controlled by the rotation unit to be proportional to an output signal of the detector. Furthermore, the present invention relates to a method of characterising a geological formation surrounding a borehole by a logging tool according to the present invention.

Dependencies are inferred from the claim text.