Rotating magnet for distance and direction measurements from a first borehole to a second borehole
First Claim
1. A method for determining the direction from a magnetic field source to an observation point, comprising:
- generating, by way of a rotating magnetic field source at a first location, an elliptically polarized magnetic field in the region of an observation point;
measuring, by first and second sensors at said observation point the amplitude and relative phase of respective first and second perpendicular vector components of said ellipticity polarized rotating magnetic field; and
determining from said measurements the direction, relative to said sensors, from said observation point to said first location.
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Accused Products
Abstract
A method for determining the distance and direction from a first borehole to a second borehole includes generating, by way of a rotating magnetic field source at a first location in a second borehole, and elliptically polarized magnetic field in the region of the first borehole. First and second sensors positioned at an observation point in the first borehole measure the amplitude and relative phase of respective first and second components of the polarized magnetic field and from these measurements, the direction, relative to the sensors, from the observation point to the first location is determined. The distance between these points is determined by measuring at plural observation points amplitude variations with depth of the rotating magnetic field in the first borehole, and computing theoretical variations in the amplitude for different assumed distances between the observation points and the location of the magnetic field source. The measured amplitude variations are compared with theoretical variations to determine the distance between the first and second boreholes.
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Citations
32 Claims
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1. A method for determining the direction from a magnetic field source to an observation point, comprising:
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generating, by way of a rotating magnetic field source at a first location, an elliptically polarized magnetic field in the region of an observation point; measuring, by first and second sensors at said observation point the amplitude and relative phase of respective first and second perpendicular vector components of said ellipticity polarized rotating magnetic field; and determining from said measurements the direction, relative to said sensors, from said observation point to said first location. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method for determining the distance and direction from a magnetic field source to an observation point, comprising:
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generating from a rotating magnetic field source at a first location an elliptically polarized magnetic field in the region of an observation point; measuring, by first and second sensors at the observation point, variations in amplitude and relative phase of respective first and second components of said polarized magnetic field; determining from said measurements the direction, relative to said sensors, from said observation point to said first location; measuring at plural observation points amplitude variations of the rotating magnetic field; computing theoretical variations in the amplitude of the rotating magnetic field for different selected distances between said observation points and said first location; and comparing the measured amplitude variations with the computed theoretical variations to determine the distance between said first location and said observation points. - View Dependent Claims (10, 11)
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12. A method for determining the distance from a first borehole to a second borehole, comprising:
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generating, by way of a rotating magnetic field source at a first location in a first borehole, an elliptically polarized magnetic field in the region of a second borehole; measuring at plural observation points in said second borehole, variations with depth in the amplitude of said polarized magnetic field; computing theoretical variations in the amplitude of the total magnetic field for different selected distances between said observation points and said first location; and comparing the measured amplitude variations with the computed theoretical variations to determine the distance between said first and second boreholes.
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13. A method for determining the distance from a first borehole to a second borehole, comprising:
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generating by way of a rotating magnetic field source at a first location in a first borehole, a rotating elliptically polarized magnetic field extending to the region of a second borehole; measuring, by first and second sensors at an observation point in said second borehole, the total rotating magnetic field; measuring at plural observation points in said second borehole the amplitude variations with depth of the total magnetic field in the second borehole; computing theoretical variations in the amplitude of the total magnetic field for different selected distances between said observation points and said first location; comparing the measured amplitude variations with the computed theoretical variations to determine the distance between said first and second boreholes; obtaining from the determined distance between said first and second boreholes and from said measured total magnetic field at said second borehole the strength of said magnetic field source; and determining from said magnetic field source strength and from the measured total magnetic field the distances from plural observation points in said second borehole to source locations in said first borehole.
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14. Apparatus for determining the direction from a magnetic field source to an observation point, comprising:
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a rotating magnetic field source at a first location, said source producing a rotating, elliptically polarized magnetic field in the earth; an observation point located in said rotating magnetic field; first and second sensors located at said observation point to measure first and second vector components of said rotating elliptically polarized magnetic field; and means for determining, from measurements of the amplitude and phase of said first and second measured components, the direction of said source with respect to said sensors. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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25. A method for determining the direction from a target borehole to a borehole being drilled, comprising:
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generating a rotating elliptically polarized magnetic field in said borehole being drilled; measuring the amplitude and relative phase of perpendicular vector components of said rotating magnetic field at an observation location in said target borehole; and determining from said vector components the direction from said borehole being drilled to said borehole being drilled. - View Dependent Claims (26, 27, 28, 29, 30, 31, 32)
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Specification