Radio frequency resistivity and dielectric constant well logging utilizing phase shift measurement
First Claim
1. A method for logging well boreholes to obtain measurements functionally related to the resistivity and dielectric constant of earth materials in the vicinity thereof, comprising the steps of:
- generating in a well borehole at a first location a radio frequency electromagnetic field in the frequency range from 10 to 60 megahertz;
detecting in the borehole at a second longitudinally spaced location from said first location the total electromagnetic field at said generated frequency and generating a first signal representative thereof;
detecting in the borehole at a third location longitudinally spaced from said first and second locations the total electromagnetic field at said generated signal frequency and generating a second signal representative thereof;
generating a third signal functionally related to the amplitude of the total electromagnetic field at least at one of said second or third locations as an indicator of the resistivity of the earth formations in the vicinity of the borehole;
generating from said first and second representative signals an indication of the relative phase shift of the total electromagnetic field at said generated frequency between said second and third locations; and
combining said phase shift indication and said third signal indicative of formation resistivity to derive an indication of the dielectric constant of the earth formations in the vicinity of the borehole.
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Abstract
The invention disclosed herein includes methods and apparatus for determining the resistivity and dielectric constant of earth materials in the vicinity of a well borehole. A radio frequency electromagnetic field in the frequency range from 20 to 40 megahertz is generated in a borehole and the total electromagnetic field at two longitudinally spaced locations is detected. Measurements of the relative phase shift in the field between the detector locations and the amplitude of the field at least at one of the detector locations may then be interpreted according to predetermined relationships in terms of the earth formation resistivity and dielectric constant.
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Citations
6 Claims
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1. A method for logging well boreholes to obtain measurements functionally related to the resistivity and dielectric constant of earth materials in the vicinity thereof, comprising the steps of:
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generating in a well borehole at a first location a radio frequency electromagnetic field in the frequency range from 10 to 60 megahertz; detecting in the borehole at a second longitudinally spaced location from said first location the total electromagnetic field at said generated frequency and generating a first signal representative thereof; detecting in the borehole at a third location longitudinally spaced from said first and second locations the total electromagnetic field at said generated signal frequency and generating a second signal representative thereof; generating a third signal functionally related to the amplitude of the total electromagnetic field at least at one of said second or third locations as an indicator of the resistivity of the earth formations in the vicinity of the borehole; generating from said first and second representative signals an indication of the relative phase shift of the total electromagnetic field at said generated frequency between said second and third locations; and combining said phase shift indication and said third signal indicative of formation resistivity to derive an indication of the dielectric constant of the earth formations in the vicinity of the borehole. - View Dependent Claims (2, 3, 4, 5, 6)
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Specification