Low inclination magnetometer bias compensation for dynamic surveying
AssigneeSchlumberger Technology Corporation
InventorsMakito Katayama, Andrew Whitmore
Life of this patent
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Abstract
A method for drilling includes rotating a BHA in a wellbore. Triaxial accelerometer and triaxial magnetometer measurements are made while rotating the BHA using corresponding triaxial accelerometer and triaxial magnetometer sets that are deployed in a roll-stabilized housing. Magnetic dip angles are computed from the accelerometer and magnetometer measurements using an inclination independent model. The computed dip angles are compared with a reference magnetic dip angle and a magnetometer bias is selected that minimizes a difference between the computed magnetic dip angles and the reference magnetic dip angle.
Claims15
A method for drilling a subterranean wellbore, the method comprising:
- rotating a bottom hole assembly (BHA) in the subterranean wellbore to drill, the BHA including a drill collar, a drill bit, a roll-stabilized housing deployed in the drill collar and configured to rotate with respect to the drill collar, and a triaxial accelerometer set and a triaxial magnetometer set deployed in the roll-stabilized housing;
- using the triaxial accelerometer set and the triaxial magnetometer set to make corresponding triaxial accelerometer measurements and triaxial magnetometer measurements while rotating the BHA;
- computing magnetic dip angles from the triaxial accelerometer measurements and triaxial magnetometer measurements using an inclination independent model that includes an unknown magnetometer bias;
- comparing the computed magnetic dip angles with a reference magnetic dip angle;
- and
- selecting a magnetometer bias that minimizes a difference between the computed magnetic dip angles and the reference magnetic dip angle.
A rotary steerable system for drilling a subterranean wellbore, the system comprising:
- a roll-stabilized housing deployed in a drill collar, the drill collar configured to rotate with a drill string, the roll-stabilized housing configured to rotate independent of the drill collar while drilling;
- a triaxial accelerometer set and a triaxial magnetometer set deployed in the roll-stabilized housing;
- and
- a controller deployed in the roll-stabilized housing, the controller configured to:
- cause the triaxial accelerometer set and the triaxial magnetometer set to make corresponding triaxial accelerometer measurements and triaxial magnetometer measurements;
- compute magnetic dip angles from the triaxial accelerometer measurements and the triaxial magnetometer measurements using an inclination independent model that includes an unknown magnetometer bias;
- compare the computed magnetic dip angles with a reference magnetic dip angle;
- and
- select a magnetometer bias that minimizes a difference between the computed magnetic dip angles and the reference magnetic dip angle.
Dependencies are inferred from the claim text.