Magnetometers for measurement-while-drilling applications
AssigneeBaker Hughes Incorporated
InventorsRobert A. Estes, Roger Cruz, Brent D. Hope, Nico Foekema
Life of this patent
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Abstract
A nuclear sensor on a bottomhole assembly (BHA) makes measurements of a property of an earth formation during continued rotation of the BHA. Magnetometers that are susceptible to bias error are deployed on the BHA to make measurements of the magnetic toolface angle. A processor separates the sensor measurements into azimuthal sectors while compensating for inherent time delays in the electronics, non-uniform rotation, and bias.
Claims39
A method of evaluating an earth formation during drilling, the method comprising:
- (a) making first measurements with an orientation sensor indicative of a toolface angle of a bottomhole assembly (BHA) during rotation thereof;
- (b) making a plurality of second measurements with a directionally sensitive formation evaluation (FE) sensor during the rotation;
- (c) correcting the plurality of second measurements using a speed of rotation of the BHA determined at least in part from the first measurements.
An apparatus for evaluating an earth formation during drilling, the apparatus comprising:
- (a) an orientation sensor on a bottomhole assembly (BHA) which makes measurements indicative of a toolface angle of the BHA during rotation thereof;
- (b) a directionally sensitive formation evaluation (FE) sensor on the BHA which makes measurements of a property of the earth formation during the rotation;
- and
- (c) a processor which corrects the plurality of second measurements using a speed of rotation of the BHA.
A machine readable medium having instructions for evaluating an earth formation, the medium comprising instructions for:
- using a first plurality of measurements made by an orientation sensor on a rotating bottom hole assembly (BHA) for correcting a second plurality of measurements made by a directionally sensitive formation evaluation (FE) sensor on the BHA using a speed of rotation of the BHA.
A method of drilling a borehole in an earth formation, the method comprising:
- (a) conveying a plurality of magnetometers into the borehole on a bottomhole assembly (BHA);
- (b) determining from outputs of the plurality of magnetometers an indication of a source of magnetic disturbance in proximity to the borehole;
- and
- (c) controlling a direction of the drilling based on said indication.
An apparatus for drilling a borehole in an earth formation, the apparatus comprising:
- (a) a bottomhole assembly (BHA) including a drill bit;
- (b) at least two magnetometers positioned at substantially opposite sides of the BHA;
- (c) a processor on the BHA which:
- (A) determines from outputs of the at least two magnetometers a magnetic field gradient, and
- (B) controlling a drilling direction of the BHA based on the determined magnetic field gradient.
Dependencies are inferred from the claim text.