US3667035A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Nuclear magnetism logging
Assignee: Texaco Development Corp
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Filing: 1970-03-17
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Granted: 1972-05-30
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Expires: 1990-03-17
Abstract
Abstract Method and apparatus for analyzing earth materials in situ along a bore hole on the basis of their nuclear magnetic properties. A logging instrument is passed through the bore hole with means to subject a region including earth material in situ to a relatively strong D.C. magnetic field, which may be oriented in any direction and which may be relatively inhomogeneous, for polarizing susceptible nuclei in said material, including selected nuclei therein. The logging instrument also contains means for applying an alternating magnetic field to the same region, including polarized nuclei therein, in a direction transverse to the earth''s magnetic field and at a frequency corresponding to the Larmor precession frequency of the selected nuclei in the earth''s field. While the alternating field is being applied, the D.C. polarizing field in the region including said material is terminated within a predetermined time interval, i.e., turned off sufficiently slowly to provide an adiabatic variation of the D.C. field and sufficiently quickly to terminate the D.C. field within a time interval less than the characteristic thermal relaxation time of the selected nuclei. Since the frequency of the alternating field is such that it produces resonance in the earth''s field alone, turning off the polarizing field sweeps the nuclei onto driven resonance. The alternating field is then abruptly terminated in said region including said polarized nuclei so that the selected polarized nuclei precess freely about the earth''s relatively homogeneous magnetic field. A characteristic of the resulting free precession condition of the selected nuclei is detected. In accordance with a preferred embodiment, the free precession condition is detected by phase coherent detection utilizing a reference signal produced in timed correlation with the alternating field. Advantageously, in accordance with a further feature of the invention, computer of average transient signal averaging techniques, such as the type known as boxcar integration (digital or analogue), are employed for enhancement of the detected free precession signal with respect to the noise.
Inventors
- 👤 Charles P Slichter
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 23:28
CPC Classifications
G; G01; G01V; G01V3/00; G01V3/18; G01V3/32
Claims Analysis
Total Claims: 33
Claim 1
Independent Claim
183 words
In a method of geophysical exploration in bore holes drilled into the earth the steps of: subjecting a region including earth material in situ to a relatively strong D.C. magnetic field, for polarizing susceptible nuclei in said material including selected nuclei therein; applying an alternating magnetic field in the same region including polarized nuclei therein in a direction transverse to the earth''s magnetic field and at a frequency corresponding to the Larmor precession frequency of the selected nuclei in the earth''s field; while said alternating field is being applied, terminating the D.C. polarizing field in said region including said material adiabatically within a predetermined time interval such that the D.C. field is terminated within a time interval less than the characteristic thermal relaxation time of the selected nuclei, thereby sweeping the selected nuclei onto driven resonance in the alternating field; then abruptly tErminating the alternating field in said region including said polarized nuclei so that the selected polarized nuclei precess freely about the earth''s magnetic field in said region; and, detecting a characteristic of the resulting free precession condition of the selected nuclei.
Claim 2
Dependent Claim
183 words
In a method of geophysical exploration in bore holes drilled into the earth the steps of: subjecting a region including earth material in situ to a relatively strong D.C. magnetic field, for polarizing susceptible nuclei in said material including selected nuclei therein; applying an alternating magnetic field in the same region including polarized nuclei therein in a direction transverse to the earth''s magnetic field and at a frequency corresponding to the Larmor precession frequency of the selected nuclei in the earth''s field; while said alternating field is being applied, terminating the D.C. polarizing field in said region including said material adiabatically within a predetermined time interval such that the D.C. field is terminated within a time interval less than the characteristic thermal relaxation time of the selected nuclei, thereby sweeping the selected nuclei onto driven resonance in the alternating field; then abruptly tErminating the alternating field in said region including said polarized nuclei so that the selected polarized nuclei precess freely about the earth''s magnetic field in said region; and, detecting a characteristic of the resulting free precession condition of the selected nuclei.
Claim 3
Dependent Claim
215 words
A well logging system for geophysical exploration in bore holes drilled into the earth comprising a well logging instrument adapted to be passed through the bore hole, said instrument including means for subjecting a region including earth material in situ to a relatively strong D.C. magnetic field, for polarizing susceptible nuclei in said material including selected nuclei therein; means for applying an alternating magnetic field in the same region including polarized nuclei therein in a direction transverse to the earth''s magnetic field and at a frequency corresponding to the Larmor precession frequency of the selected nuclei in the earth''s field; said system including means for terminating the D.C. polarizing field in said region including said material adiabatically while said alternating field is being applied and within a predetermined time interval such that the D.C. field is terminated within a time interval less than the characteristic thermal relaxation time of the selected nuclei, thereby sweeping the selected nuclei onto driven resonance in the alternating field; said system further including means for then abruptly terminating the alternating field in said region including said polarized nuclei so that the selected polarized nuclei precess freely about the earth''s magnetic field in said region; and, means for detecting a characteristic of the resulting free precession condition of the selected nuclei.
Claim 4
Dependent Claim
215 words
A well logging system for geophysical exploration in bore holes drilled into the earth comprising a well logging instrument adapted to be passed through the bore hole, said instrument including means for subjecting a region including earth material in situ to a relatively strong D.C. magnetic field, for polarizing susceptible nuclei in said material including selected nuclei therein; means for applying an alternating magnetic field in the same region including polarized nuclei therein in a direction transverse to the earth''s magnetic field and at a frequency corresponding to the Larmor precession frequency of the selected nuclei in the earth''s field; said system including means for terminating the D.C. polarizing field in said region including said material adiabatically while said alternating field is being applied and within a predetermined time interval such that the D.C. field is terminated within a time interval less than the characteristic thermal relaxation time of the selected nuclei, thereby sweeping the selected nuclei onto driven resonance in the alternating field; said system further including means for then abruptly terminating the alternating field in said region including said polarized nuclei so that the selected polarized nuclei precess freely about the earth''s magnetic field in said region; and, means for detecting a characteristic of the resulting free precession condition of the selected nuclei.
Claim 5
Dependent Claim
83 words
Apparatus as defined in claim 2 wherein the means for applying the alternating field in the region including said polarized nuclei includes: a source of alternating current oscillations coupled to a coil in said logging instrument; and wherein said means for detecting a characteristic of the resulting free precession condition of the selected nuclei further includes a phase coherent detector coupled to said source of oscillations for deriving therefrom a reference signal in timed correlation with the alternating field applied to said region.
Claim 6
Dependent Claim
24 words
Apparatus as defined in claim 3 further comprising a transient integrating type signal enhancement system coupled to the output of said phase coherent detector.
Claim 7
Dependent Claim
106 words
Apparatus as defined in claim 3 further comprising magnetometer apparatus including a magnetometer head associated with said well logging instrument for measuring the value of the earth''s magnetic field in said bore hole, said logging system further comprising means coupled to said magnetometer for controlling the frequency of said source of alternating current oscillations in response to the value of the earth''s field in the vicinity of said logging instrument so that said alternating magnetic field applied to the region under investigation is maintained substantially at the Larmor precession frequency of the selected nuclei in the earth''s field from place to place throughout the bore hole.
Claim 8
Dependent Claim
57 words
Apparatus as defined in claim 5 wherein said magnetometer is of the magnetic resonance type and which includes a magnetometer oscillator whose output frequency is maintained substantially at the Larmor frequency for selected nuclei contained in a preselected sample of material positioned in said magnetometer head and subjected to the earth''s magnetic field in said bore hole.
Claim 9
Dependent Claim
190 words
A well logging system for geophysical exploration in bore holes drilled into the earth comprising a well logging instrument adapted to be passed through the bore hole, said instrument including means for subjecting material to a relatively strong D.C. magnetic field for polarizing susceptible nuclei therein; means for applying an alternating magnetic field to said material including polarized nuclei therein in a direction transverse to the earth''s magnetic field and at a freqUency corresponding substantially to the Larmor precession frequency of the selected nuclei in the earth''s field; said system including means for terminating the D.C. polarizing field applied to said material adiabatically while said alternating field is being applied and within a time interval less than the characteristic thermal relaxation time of the selected nuclei, thereby sweeping the selected nuclei onto driven resonance in the alternating field; said system further including means for then abruptly terminating the alternating field applied to said material including said polarized nuclei so that the selected polarized nuclei precess freely about the earth''s magnetic field in said material; and means for detecting a characteristic of the resulting free precession condition of the selected nuclei.
Claim 10
Dependent Claim
190 words
A well logging system for geophysical exploration in bore holes drilled into the earth comprising a well logging instrument adapted to be passed through the bore hole, said instrument including means for subjecting material to a relatively strong D.C. magnetic field for polarizing susceptible nuclei therein; means for applying an alternating magnetic field to said material including polarized nuclei therein in a direction transverse to the earth''s magnetic field and at a freqUency corresponding substantially to the Larmor precession frequency of the selected nuclei in the earth''s field; said system including means for terminating the D.C. polarizing field applied to said material adiabatically while said alternating field is being applied and within a time interval less than the characteristic thermal relaxation time of the selected nuclei, thereby sweeping the selected nuclei onto driven resonance in the alternating field; said system further including means for then abruptly terminating the alternating field applied to said material including said polarized nuclei so that the selected polarized nuclei precess freely about the earth''s magnetic field in said material; and means for detecting a characteristic of the resulting free precession condition of the selected nuclei.
Claim 11
Dependent Claim
19 words
Apparatus as defined in claim 7 wherein said material is included in earth formations in situ along the borehole.
Claim 12
Dependent Claim
58 words
Apparatus as defined in claim 7 wherein said material comprises a preselected sample contained within said logging instrument, and wherein means are provided for deriving a signal indicative of the precise value of the Larmor frequency of the nuclei in free precession, thereby providing a measure of the earth''s field applied to said sample in the logging instrument.
Claim 13
Dependent Claim
30 words
Apparatus as defined in claim 2 wherein said means for detecting a characteristic of the resulting free precession condition of the selected nuclei includes a transient integrating signal enhancement system.
Claim 14
Dependent Claim
18 words
Apparatus as defined in claim 4 wherein said transient integrating signal enhancement system includes an analog boxcar integrator.
Claim 15
Dependent Claim
18 words
Apparatus as defined in claim 10 wherein said transient integrating signal enhancement system includes an analog boxcar integrator.
Claim 16
Dependent Claim
18 words
Apparatus as defined in claim 4 wherein said transient integrating signal enhancement system includes a digital boxcar integrator.
Claim 17
Dependent Claim
18 words
Apparatus as defined in claim 10 wherein said transient integrating signal enhancement system includes a digital boxcar integrator.
Claim 18
Dependent Claim
20 words
Apparatus as defined in claim 4 wherein said transient integrating signal enhancement system includes a multi-channel computer of average transients.
Claim 19
Dependent Claim
20 words
Apparatus as defined in claim 10 where said transient integrating signal enhancement system includes a multi-channel computer of average transients.
Claim 20
Dependent Claim
219 words
A well logging system for geophysical exploration in boreholes drilled into the earth comprising a well logging instrument adapted to be passed through the borehole, said instrument including means for subjecting a region including earth material in situ to a relatively strong D.C. magnetic field, for polarizing susceptible nuclei in said material including selected nuclei therein; said system including means for terminating the D.C. polarizing field in said region including said material adiabatically within a predetermined time interval such that the D.C. field is terminated within a time interval less than the characteristic thermal relaxation time of the selected nuclei; means for applying an alternating field in the same region including polarized nuclei therein in a direction transverse to the earth''s magnetic field and at a frequency corresponding to the Larmor precession frequency of the selected nuclei in the earth''s field; said system further including means for then abruptly terminating the alternating field in said region including said polarized nuclei so that the selected polarized nuclei precess freely about the earth''s magnetic field in said region; and, means comprising a phase coherent mixer for detecting a characteristic of the resulting free precession condition of the selected nuclei, said phase coherent mixer including means for deriving a reference signal in timed correlation with the alternating field applied to said region.
Claim 21
Dependent Claim
219 words
A well logging system for geophysical exploration in boreholes drilled into the earth comprising a well logging instrument adapted to be passed through the borehole, said instrument including means for subjecting a region including earth material in situ to a relatively strong D.C. magnetic field, for polarizing susceptible nuclei in said material including selected nuclei therein; said system including means for terminating the D.C. polarizing field in said region including said material adiabatically within a predetermined time interval such that the D.C. field is terminated within a time interval less than the characteristic thermal relaxation time of the selected nuclei; means for applying an alternating field in the same region including polarized nuclei therein in a direction transverse to the earth''s magnetic field and at a frequency corresponding to the Larmor precession frequency of the selected nuclei in the earth''s field; said system further including means for then abruptly terminating the alternating field in said region including said polarized nuclei so that the selected polarized nuclei precess freely about the earth''s magnetic field in said region; and, means comprising a phase coherent mixer for detecting a characteristic of the resulting free precession condition of the selected nuclei, said phase coherent mixer including means for deriving a reference signal in timed correlation with the alternating field applied to said region.
Claim 22
Dependent Claim
197 words
In a method of geophysical exploration in boreholes drilled into the earth the steps of: subjecting a region including earth material in situ to a relatively strong D.C. magnetic field, for polarizing susceptible nuclei in said material including selected nuclei therein; terminating the D.C. polarizing field in said region including said material adiabatically within a predetermined time interval such that the D.C. field is terminated within a time interval less than the characteristic thermal relaxation time of the selected nuclei; applying an alternating magnetic field in the same region including polarized nuclei therein in a direction transverse to the earth''s magnetic field and at a frequency corresponding to the Larmor precession frequency of the selected nuclei in the earth''s field; then abruptly terminating the alternating field in said region including said polarized nuclei so that the selected polarized nuclei precess freely about the earth''s magnetic field in said region; and, detecting a characteristic of the resulting free precession condition of the selected nuclei by deriving a signal corresponding to the detected characteristic by deriving a reference signal in timed correlation with the alternating field applied to said region and subjecting the derived signal to phase coherent mixing.
Claim 23
Dependent Claim
197 words
In a method of geophysical exploration in boreholes drilled into the earth the steps of: subjecting a region including earth material in situ to a relatively strong D.C. magnetic field, for polarizing susceptible nuclei in said material including selected nuclei therein; terminating the D.C. polarizing field in said region including said material adiabatically within a predetermined time interval such that the D.C. field is terminated within a time interval less than the characteristic thermal relaxation time of the selected nuclei; applying an alternating magnetic field in the same region including polarized nuclei therein in a direction transverse to the earth''s magnetic field and at a frequency corresponding to the Larmor precession frequency of the selected nuclei in the earth''s field; then abruptly terminating the alternating field in said region including said polarized nuclei so that the selected polarized nuclei precess freely about the earth''s magnetic field in said region; and, detecting a characteristic of the resulting free precession condition of the selected nuclei by deriving a signal corresponding to the detected characteristic by deriving a reference signal in timed correlation with the alternating field applied to said region and subjecting the derived signal to phase coherent mixing.
Claim 24
Dependent Claim
30 words
Apparatus as defined in claim 17 wherein said means for detecting a characteristic of the resulting free precession condition of the selected nuclei includes a transient integrating signal enhancement system.
Claim 25
Dependent Claim
18 words
Apparatus as defined in claim 19 wherein said transient integrating signal enhancement system includes an analog boxcar integrator.
Claim 26
Dependent Claim
18 words
Apparatus as defined in claim 19 wherein said transient integrating signal enhancement system includes a digital boxcar integrator.
Claim 27
Dependent Claim
20 words
Apparatus as defined in claim 19 wherein said transient integrating signal enhancement system includes a multi-channel computer of average transients.
Claim 28
Dependent Claim
47 words
A well logging system as defined in claim 2 wherein the means for subjecting said region in situ to a relatively strong D.C. magnetic field includes first coil means, and wherein the means for detecting a characteristic of the resulting free precession condition includes second coil means.
Claim 29
Dependent Claim
45 words
A well logging system as defined in claim 7 wherein the means for subjecting said material to a relatively strong D.C. magnetic field includes first coil means and wherein the means for detecting a characteristic of the resulting free precession condition includes second coil means.
Claim 30
Dependent Claim
47 words
A well logging system as defined in claim 17 wherein the means for subjecting said region in situ to a relatively strong D.C. magnetic field includes first coil means, and wherein the means for detecting a characteristic of the resulting free precession condition includes second coil means.
Claim 31
Dependent Claim
25 words
A well logging system as defined in claim 23 wherein the means for applying an alternating field in the same region includes third coil means.
Claim 32
Dependent Claim
24 words
A well logging system as defined in claim 24 wherein the means for applying an alternating field to said material includes third coil means
Claim 33
Dependent Claim
24 words
A well logging system as defined in claim 25 wherein the means for applying an alternating field to said material includes third coil means.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-05-30 | 1975-11-29 | 1976-05-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-05-30 | 1979-11-29 | 1980-05-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-05-30 | 1983-11-29 | 1984-05-30 | $7700.00 | Window Closed / Lapsed |