Compensation of magnetic influence in a MWD system
AssigneeBaker Hughes Incorporated
InventorsThomas Kruspe, Volker Krueger, Martin Blanz, Roland E. Chemali
Life of this patent
Estimating the term…
Abstract
The present disclosure provides a downhole tool that includes a magnetometer and a nuclear magnetic resonance (NMR) sensor. One or more compensating magnets are provided on the tool to cancel or offset the effect of the magnetic field of the magnets of the NMR sensor on the magnetometer measurements made during drilling of a wellbore. The compensating magnets may have the same magnetic field characteristics as the sensor magnets and may be made of the same material.
Claims25
An apparatus configured to correct for an effect of a source of a magnetic disturbance on a downhole assembly conveyed in a borehole in the earth formation, the apparatus comprising:
- at least one magnet on the downhole assembly configured to produce a magnetic field at a selected location on the downhole assembly that substantially cancels a magnetic field produced by the source of the magnetic disturbance, the at least one magnet not being part of a nuclear magnetic resonance sensor and further configured so that a gradient of the magnetic field produced by the at least one magnet substantially cancels a gradient of the magnetic field produced by the source of the disturbance.
A method of correcting for an effect of a source of a magnetic disturbance on a downhole assembly conveyed in a borehole in the earth formation, the method comprising:
- positioning at least one magnet that is not part of a nuclear magnetic resonance sensor on the downhole assembly to produce a magnetic field at the selected location that, at a selected location:
- (A) substantially cancels a magnetic field produced by the source of the magnetic disturbance, and
- (B) a gradient of the magnetic field produced by the at least one magnet substantially cancels a gradient of the magnetic field produced by the source of the disturbance.
Dependencies are inferred from the claim text.