Plural sensor magnetometer arrangement for extended lateral range electrical conductivity logging
First Claim
1. A magnetometer for use in measuring subsurface A.C. injected magnetic fields for borehole logging, comprising;
- first and second magnetic field sensors, said first sensor lying in a first plane and said second sensor lying in a second plane;
fastening means for securing said sensors in axial alignment with the plane of said first sensor perpendicular to the plane of said second sensor;
an elongated heat-insulating housing adapted to receive said sensors, said housing having a relatively small diameter and being adapted for insertion vertically into a borehole;
said first and second sensors each including;
first and second generally U-shaped core segments each having first and second spaced, parallel, elongated leg portions extending from opposite ends of a relatively short base portion, said first and second core segments being arranged in back-to-back relationship with their base portions abutting each other;
channel means securing corresponding leg portions of said core segments to hold said segments in assembled relationship to form a generally H-shaped core having elongated leg portions extending parallel to, and defining, the sensor axis; and
coil means surrounding said abutting base portions;
circuit means connected to the coil means of each said sensor for producing signals representing A.C. magnetic field components detected by said first and second sensors; and
means for securing said circuit means on at least one of said sensors.
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Accused Products
Abstract
A method of well logging in petroleum exploration and apparatus for use in the method is described. An improved magnetometer is disposed in a well bore to provide indications of the distribution, filimentation, and distortion of a controlled current flow within adjoining strata of interest. The current flow is excited by a distant alternating source located at the surface or at other boreholes, and perturbations in the current flow and accompanying magnetic field caused by the electrical characteristics of the adjoining strata are registered by the magnetometer.
The magnetometer comprises two pairs of elongated U-shaped cores of laminated, high-permeability metal, adjacent portions of each pair being surrounded by a sensing coil. The coil outputs are fed to surface equipment for detection and analysis.
128 Citations
20 Claims
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1. A magnetometer for use in measuring subsurface A.C. injected magnetic fields for borehole logging, comprising;
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first and second magnetic field sensors, said first sensor lying in a first plane and said second sensor lying in a second plane; fastening means for securing said sensors in axial alignment with the plane of said first sensor perpendicular to the plane of said second sensor; an elongated heat-insulating housing adapted to receive said sensors, said housing having a relatively small diameter and being adapted for insertion vertically into a borehole; said first and second sensors each including; first and second generally U-shaped core segments each having first and second spaced, parallel, elongated leg portions extending from opposite ends of a relatively short base portion, said first and second core segments being arranged in back-to-back relationship with their base portions abutting each other; channel means securing corresponding leg portions of said core segments to hold said segments in assembled relationship to form a generally H-shaped core having elongated leg portions extending parallel to, and defining, the sensor axis; and coil means surrounding said abutting base portions; circuit means connected to the coil means of each said sensor for producing signals representing A.C. magnetic field components detected by said first and second sensors; and means for securing said circuit means on at least one of said sensors. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A magnetometer system for measuring A.C. injected magnetic fields for borehole logging, comprising:
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surface means for producing in subsurface strata an A.C. magnetic field; first and second magnetic field sensors, each sensor including first and second generally U-shaped core segments each having first and second spaced, parallel, elongated leg portions extending from opposite ends of a relatively short base portion, said first and second core segments with their base portions abutting each other, channel means securing corresponding leg portions of said core segments being arranged in back-to-back relationships to hold said segments in assembled relationship to form a generally H-shaped core having elongated leg portions extending parallel to, and defining, the sensor axis, and coil means surrounding said abutting base portions; fastening means for securing said sensors in axial alignment with the plane of said first sensor being perpendicular to the plane of said second sensor; an elongated housing for said sensors, said housing having a relatively small diameter and being adapted for insertion vertically into a borehole; notch filter means for passing signals having the frequency of said A.C. magnetic fields; multiplexer switching means connecting the output of a selected one of said sensor coils to the input of said notch filter; surface data processing equipment; cable means for connecting said magnetometer to said surface data processing equipment; and transmitter means responsive to the output from said notch filter to transmit to said surface equipment signals corresponding to said A.C. magnetic fields. - View Dependent Claims (15, 16, 17, 18, 19, 20)
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Specification