Apparatus and method for determining parameters of formations surrounding a borehole in a preselected direction
First Claim
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1. A method of directional induction logging employing electromagnetic induction, comprising the steps of:
- arranging at least one directional transmitting coil having an axis and at least one directional receiving coil having an axis in a borehole along an axis of the borehole such that a preselected angle between said bore axis and the respective axes of said coils is less than ninety degrees;
measuring the amplitude of a voltage induced in said at least one receiving coil; and
measuring the phase difference between current supplied to said at least one transmitting coil and current induced in said at least one receiving coil;
whereby electrical conductivity of a formation around said borehole is measured in a preselected direction due to said angular arrangement of said coils.
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Abstract
At least one transmitting coil 1 and at least one receiving coil 2 are disposed along the bore axis 18 of a borehole 7 such that these coils are inclined and face each other, thus causing these coils to have directivity for examining electric characteristics of a formation around the borehole. More specifically, a method of and an apparatus for directional induction logging are provided, which permit measurement of the electric conductivity distribution of a formation in the circumferential direction in a range of several meters around the borehole and also imaging reflecting the electric conductivity.
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Citations
6 Claims
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1. A method of directional induction logging employing electromagnetic induction, comprising the steps of:
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arranging at least one directional transmitting coil having an axis and at least one directional receiving coil having an axis in a borehole along an axis of the borehole such that a preselected angle between said bore axis and the respective axes of said coils is less than ninety degrees; measuring the amplitude of a voltage induced in said at least one receiving coil; and measuring the phase difference between current supplied to said at least one transmitting coil and current induced in said at least one receiving coil; whereby electrical conductivity of a formation around said borehole is measured in a preselected direction due to said angular arrangement of said coils. - View Dependent Claims (2, 3)
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4. An apparatus for directional induction logging, comprising at least one directional transmitting coil having an axis and at least one directional receiving coil having an axis which are disposed in a borehole along an axis of the borehole;
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said coils being arranged with respect to said axis of said borehole at a preselected angle where the respective axes of said coils are disposed at less than ninety degrees with respect to said axis of said borehole; whereby the amplitude of a voltage induced in said at least one receiving coil being measured; and whereby the phase difference between current supplied to said at least one transmitting coil and current induced in said at least one receiving coil being measured; whereby electrical conductivity of a formation around said borehole is measured in a preselected direction due to said angular arrangement of said coils. - View Dependent Claims (5, 6)
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Specification