Alternating and static magnetic field gradient measurements for distance and direction determination
First Claim
1. Apparatus for determining the distance and direction of a first well with respect to a second nearby well, comprising:
- a sensor tool located in a first well, said sensor tool having an axis extending along the length of said first well;
means producing at least one static magnetic field having its origin at said second well and extending radially from said second well at least to said first well;
sensor means comprising two ring core fluxgate magnetometers located at diametrically opposite sides of said sensor tool, said magnetometers measuring corresponding magnetic field vectors of said at least one magnetic field for measuring a field gradient of said magnetic field perpendicular to said sensor tool axis; and
means for determining the orientation of said sensor tool with respect to said magnetic field, the measured gradient of said field corresponding to the distance between said first and second wells and said determined orientation of said sensor corresponding to the direction to said second well from said first well.
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Accused Products
Abstract
Magnetic field gradient sensing apparatus utilizing highly sensitive fluxgate magnetometers permit direct determination of the distance between two well bores and for determining the direction from one bore to the other. The gradient sensing apparatus may be responsive to alternating magnetic fields resulting from current flow in a steel casing within a target well and measured by two fluxgate magnetometers diametrically oppositely located in a sensor tool and oriented to measure the vector components of the alternating field at opposite sides of the tool to thereby obtain a measure of the gradient of the field across the diameter of the tool. Field gradient sensing apparatus may also be used to measure the gradient of a static magnetic field having a radial gradient, wherein the static field is produced by ferromagnetic materials in the target well. Again, a pair of magnetometers is utilized to measure the field gradient across the diameter of the sensor to determine distance and direction to the target. Both static and alternating magnetic fields may be simultaneously measured for improved accuracy and reliability.
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Citations
16 Claims
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1. Apparatus for determining the distance and direction of a first well with respect to a second nearby well, comprising:
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a sensor tool located in a first well, said sensor tool having an axis extending along the length of said first well; means producing at least one static magnetic field having its origin at said second well and extending radially from said second well at least to said first well; sensor means comprising two ring core fluxgate magnetometers located at diametrically opposite sides of said sensor tool, said magnetometers measuring corresponding magnetic field vectors of said at least one magnetic field for measuring a field gradient of said magnetic field perpendicular to said sensor tool axis; and means for determining the orientation of said sensor tool with respect to said magnetic field, the measured gradient of said field corresponding to the distance between said first and second wells and said determined orientation of said sensor corresponding to the direction to said second well from said first well. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method for determining the distance from a first well to a second, nearby well, comprising:
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producing a static magnetic field having its origin at said second well and extending radially with respect to said second well at least to said first well; locating a first plurality of sensor coils within a sensor located in said first well; measuring the field vectors of said produced magnetic field within a horizontal plane through said sensor located in said first well; determining from said field vectors the horizontal magnetic field gradient within said sensor; and determining from said field gradient the distance to said second well. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15, 16)
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Specification