Azimuth determination for vector sensor tools
First Claim
1. In mapping or survey apparatus using a single inertial angular rate sensor and a single acceleration sensor, one or both with input axes of sensitivity nominally canted relative to a well or borehole axis, rotated about the borehole axis and both sensors having outputs, the combination comprising(a) means responsive to the accleration sensor output together with the inertial angular rate sensor output to compute from the rate sensor output the components thereof in the horizontal plane and the vertical plane, and(b) means to derive azimuth as the Arcsin of the component of sensed inertial angular rate in the horizontal plane normal to the plane containing the borehole axis and the gravity vector divided by the horizontal plane component of the earth'"'"'s angular velocity vector.
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Abstract
This invention relates to mapping or survey apparatus and methods, and more particularly concerns derivation of the azimuth output indications for such apparatus in a borehole from the outputs or output indications of either an inertial angular rate vector sensor (or sensors) and an acceleration vector sensor (or sensors), or a magnetic field vector sensor (or sensors), and from the outputs of an acceleration vector sensor (or sensors). At least one of such sensors in any instrument may be canted relative to the borehole axis. Borehole tilt is also derived.
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Citations
41 Claims
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1. In mapping or survey apparatus using a single inertial angular rate sensor and a single acceleration sensor, one or both with input axes of sensitivity nominally canted relative to a well or borehole axis, rotated about the borehole axis and both sensors having outputs, the combination comprising
(a) means responsive to the accleration sensor output together with the inertial angular rate sensor output to compute from the rate sensor output the components thereof in the horizontal plane and the vertical plane, and (b) means to derive azimuth as the Arcsin of the component of sensed inertial angular rate in the horizontal plane normal to the plane containing the borehole axis and the gravity vector divided by the horizontal plane component of the earth'"'"'s angular velocity vector.
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4. In mapping or survey apparatus using two axis inertial angular rate sensor means and two-axis acceleration sensor means both with their two input axes of sensitivity nominally normal to a well or borehole axis, both sensors having outputs,
(a) means responsive to acceleration sensor outputs together with the inertial angular rate sensor outputs to compute from the rate sensor outputs the components thereof in the horizontal and vertical plane, and (b) means to derive azimuth as the Arcsin of the component of sensed inertial angular rate in the horizontal plane normal to the plane containing the borehole axis and the gravity vector divided by the horizontal plane component of the earth'"'"'s angular velocity vector.
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15. In borehole survey apparatus wherein angular rate sensor means and acceleration sensor means are suspended and effectively rotated in a borehole, at least one of said sensors canted at an angle γ
- relative to the borehole axis, the angular rate sensor means having amplitude output GA, and rotation related phase output GP, and the acceleration sensor means having amplitude output AA and rotation related phase output AP, there also being means supplying a signal value Ω
v proportional to earth'"'"'s angular rate of rotation, and means supplying a value derived from γ
, the improvement which comprises(a) first means for combining AA, AP, GA, GP, said value derived from γ
, and Ω
v, to derive a value ψ
for borehole azimuth at the level of said sensor means in the borehole. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 25, 32, 33, 34, 35, 36, 37, 38, 39, 40)
- relative to the borehole axis, the angular rate sensor means having amplitude output GA, and rotation related phase output GP, and the acceleration sensor means having amplitude output AA and rotation related phase output AP, there also being means supplying a signal value Ω
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23. In well bore survey apparatus wherein angular rate sensor means and accelerometer means are located in a borehole and at a cant angle γ
- relative to the borehole axis, the angular rate sensor means having amplitude output GA and phase output GP, and the accelerometer means having amplitude output AA and phase output AP, there being means providing a value Ω
v proportional to earth'"'"'s angular velocity vector, and means supplying the combination comprising values derived from γ
,(a) means operatively connection to said sensors to be responsive to GA, GP and AP and a value derived from γ
to derive a first component Ω
x of the angular rate sensor output,(b) means operatively connected to said sensors to be responsive to GA, GP and AP and a value derived from γ
to derive a second component Ω
y of the angular rate sensor output,(c) means operatively connected to said (a) means to be responsive to Ω
x, AA and Ω
v to derive a value Ω
'"'"'B, and(d) means operatively connected to said (b) and (c) means to derive ψ
from Ω
y and Ω
'"'"'Bwherein ψ
is an azimuth value indicative of the azimuth angle of the borehole relative to the true North at the location of said sensor means. - View Dependent Claims (24)
- relative to the borehole axis, the angular rate sensor means having amplitude output GA and phase output GP, and the accelerometer means having amplitude output AA and phase output AP, there being means providing a value Ω
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26. In borehole survey apparatus wherein magnetic sensor means and acceleration sensor means are suspended and effectively rotated in a borehole and at a cant angle γ
- relative to the borehole axis, the magnetic sensor means having amplitude output GA and rotation related phase output GP, and the acceleration sensor means having amplitude output AA and rotation related phase output AP, there also being means supplying a signal value Ω
v proportional to earth'"'"'s angular rate of rotation, and means supplying a value derived from γ
the improvement which comprises(a) first means for combining AA, AP, GA, GP said value derived from γ and
Ω
v to derive a value ψ
for borehole azimuth at the level of said sensor means in the borehole. - View Dependent Claims (27, 28, 29, 30, 31)
- relative to the borehole axis, the magnetic sensor means having amplitude output GA and rotation related phase output GP, and the acceleration sensor means having amplitude output AA and rotation related phase output AP, there also being means supplying a signal value Ω
Specification