US3758848A
Expired / Lapsed
US
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Magnetic susceptibility well logging system and method with automatic null control
Assignee: Texaco Inc
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Filing: 1971-12-27
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Granted: 1973-09-11
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Expires: 1991-12-27
Abstract
Abstract An automatic null control circuit and method is employed in a magnetic susceptibility well loging system for regulating the null voltage employed to cancel the exciter voltage component of the receiver coil signal. Means and method are provided for determining the amplitude difference between the null voltage and the exciter voltage component, whereby the null voltage is multiplied by a factor which is functionally related to the difference. Since the null and receiver coil signals are both AC, the amplitude difference is also a phase-dependent function. Accordingly, it is an adjunct of the automatic null control system and method to also monitor and correct for phase difference between the null and receiver voltages.
Inventors
- 👤 D Dowling
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 13:37
CPC Classifications
G; G01; G01V; G01V3/00; G01V3/18; G01V3/26; G01V3/28
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
159 words
In a logging system for determining the magnetic susceptibility of a subsurface earth formation traversed by a borehole, the combination comprising an AC power supply for providing an exciter voltage, a transmitting inductance for generating an electromagnetic field in said borehole and formation in response to said exciter voltage, a receiving inductance for deriving from said field a receiver voltage having components attributable to said exciter voltage and to the magnetic susceptibility of said formation, a null inductance for deriving a null voltage opposite in phase and functionally related in amplitude to said exciter voltage component of said receiver voltage, correction means for detecting a difference in amplitude between said null voltage and said exciter voltage component and for adjusting the amplitude of said null voltage to coincide with the amplitude of said exciter voltage component, and canceling means responsive to said receiver voltage and said adjusted null voltage for canceling said exciter voltage component of said receiver voltage.
Claim 2
Dependent Claim
159 words
In a logging system for determining the magnetic susceptibility of a subsurface earth formation traversed by a borehole, the combination comprising an AC power supply for providing an exciter voltage, a transmitting inductance for generating an electromagnetic field in said borehole and formation in response to said exciter voltage, a receiving inductance for deriving from said field a receiver voltage having components attributable to said exciter voltage and to the magnetic susceptibility of said formation, a null inductance for deriving a null voltage opposite in phase and functionally related in amplitude to said exciter voltage component of said receiver voltage, correction means for detecting a difference in amplitude between said null voltage and said exciter voltage component and for adjusting the amplitude of said null voltage to coincide with the amplitude of said exciter voltage component, and canceling means responsive to said receiver voltage and said adjusted null voltage for canceling said exciter voltage component of said receiver voltage.
Claim 3
Dependent Claim
69 words
The system described in claim 1, wherein said correction and canceling means include difference means interconnected with said receiving and null inductances for deriving a difference voltage functionally related to any difference in amplitude between said null voltage and said receiver voltage, and adjustment means interconnected between said null inductance and said difference means for varying the amplitude of Said null voltage as a function of said difference voltage.
Claim 4
Dependent Claim
76 words
The system described in claim 2, wherein said adjustment means further includes phase sensitive means responsive to said difference voltage and said exciter voltage for deriving a recordable signal functionally related to the magnetic susceptibility of said formation, and multiplying means responsive to said recordable signal for multiplying said null voltage by a factor which is a function of said detected amplitude difference between said null voltage and said exciter voltage component of said receiver voltage.
Claim 5
Dependent Claim
51 words
The system described in claim 3, wherein said adjustment means further includes phase correction means interconnected between said null inductance means and said multiplying means for detecting the occurrence of any phase difference between said null and receiver voltages and for realigning said null voltage into phase with said receiver voltage.
Claim 6
Dependent Claim
72 words
The system described in claim 4, wherein said phase correction means includes phase monitoring means interconnected between said difference means and said multiplying means for detecting the occurrence and magnitude of any phase difference between said receiver voltage and said multiplied null voltage, and phase alignment means interconnected between said null inductance means and said multiplying means for adjusting the phase of said null voltage in response to said phase monitoring means.
Claim 7
Dependent Claim
151 words
In a logging system for determining the magnetic susceptibility of a subsurface earth formation traversed by a borehole, the combination comprising an AC power supply for providing an exciter voltage, a transmitting inductance for generating an electromagnetic field in said borehole and formation in response to said exciter voltage, a receiving inductance for deriving from said field a receiver voltage having components attributable to said exciter voltage and to the magnetic susceptibility of said formation, a null inductance for deriving a null voltage opposite in phase and at least substantially equal in magnitude to said exciter voltage component of said receiver voltage, comparison means for deriving a difference voltage functionally related in magnitude to the difference amplitude between said null and receiver voltages, and null regulating means responsive to said difference voltage for maintaining a predetermined amplitude relationship between said null voltage and said exciter voltage component of said receiver voltage.
Claim 8
Dependent Claim
151 words
In a logging system for determining the magnetic susceptibility of a subsurface earth formation traversed by a borehole, the combination comprising an AC power supply for providing an exciter voltage, a transmitting inductance for generating an electromagnetic field in said borehole and formation in response to said exciter voltage, a receiving inductance for deriving from said field a receiver voltage having components attributable to said exciter voltage and to the magnetic susceptibility of said formation, a null inductance for deriving a null voltage opposite in phase and at least substantially equal in magnitude to said exciter voltage component of said receiver voltage, comparison means for deriving a difference voltage functionally related in magnitude to the difference amplitude between said null and receiver voltages, and null regulating means responsive to said difference voltage for maintaining a predetermined amplitude relationship between said null voltage and said exciter voltage component of said receiver voltage.
Claim 9
Dependent Claim
52 words
The system described in claim 6, wherein said null regulating means further includes phase regulating means for maintaining a predetermined phase relationship between said null and receiver voltages, and amplitude regulating means for maintaining a predetermined amplitude relationship between said phase-regulated null voltage and said exciter voltage component of said receiver voltage.
Claim 10
Dependent Claim
69 words
The system described in claim 7, wherein said amplitude regulating means further includes a phase sensitive detector for deriving a DC voltage functionally related to the amplitude difference between said exciter voltage from said AC power supply and said difference voltage from said comparison means, and multiplying means for multiplying the amplitude of said phase-regulated null voltage by a function of said DC voltage from said phase sensitive detector.
Claim 11
Dependent Claim
124 words
The system described in claim 7, wherein said multiplying means further includes a DC amplifier interconnected with said phase sensitive detector for generating a function voltage having an amplitude functionally related to said DC voltage from said phase sensitive detector, a multiplier having one input coupled to receive said function voltage from said DC amplifier and another input coupled to receive said phase-regulated null voltage for providing an output voltage functionally related in amplitude to the product of the amplitudes of said function voltage and said phase-reGulated null voltage, and a gain restoring amplifier interconnected between said multiplier and said comparison means for generating and applying to said comparison means an amplitude-regulated null voltage corresponding to the exciter voltage component of said receiver voltage.
Claim 12
Dependent Claim
86 words
The system described in claim 9, wherein said phase regulating means includes a phase detector for deriving an AC phase measurement voltage functionally related in amplitude to any phase difference between said amplitude-regulated voltage and said exciter voltage, a semiconductance interconnected to establish a phase-shifting capacitance between said null inductance and said multiplier, and a DC voltage means responsive to said phase detector for generating a control voltage to regulate the magnitude of said gain-shifting capacitance in functional relationship to the magnitude of said phase-measurement voltage.
Claim 13
Independent Claim
137 words
A method for determining the magnetic susceptibility of a subsurface earth formation traversed by a borehole, comprising generating an AC exciter voltage, generating an electromagnetic field in said borehole and formation in response to said exciter voltage, deriving from said field a receiver voltage having components attributable to said exciter voltage and to the magnetic susceptibility of said formation, deriving a null voltage opposite in phase and functionally related in amplitude to said exciter voltage component of said receiver voltage, detecting a difference in amplitude between said null voltage and said exciter voltage component and adjusting the amplitude of said null voltage to coincide with the amplitude of said exciter voltage component, and canceling said exciter voltage component of said receiver voltage as a function of the difference between said receiver voltage and said adjusted null voltage.
Claim 14
Independent Claim
137 words
A method for determining the magnetic susceptibility of a subsurface earth formation traversed by a borehole, comprising generating an AC exciter voltage, generating an electromagnetic field in said borehole and formation in response to said exciter voltage, deriving from said field a receiver voltage having components attributable to said exciter voltage and to the magnetic susceptibility of said formation, deriving a null voltage opposite in phase and functionally related in amplitude to said exciter voltage component of said receiver voltage, detecting a difference in amplitude between said null voltage and said exciter voltage component and adjusting the amplitude of said null voltage to coincide with the amplitude of said exciter voltage component, and canceling said exciter voltage component of said receiver voltage as a function of the difference between said receiver voltage and said adjusted null voltage.
Claim 15
Dependent Claim
47 words
The method described in claim 11, wherein said correction and canceling steps include deriving a differnce voltage functionally related to any difference in amplitude between said null voltage and said receiver voltage, and adjusting the amplitude of said null voltage as a function of said difference voltage.
Claim 16
Dependent Claim
63 words
The method described in claim 12, wherein said adjustment step further includes deriving from said difference voltage and said exciter voltage a recordable signal functionally related to the magnetic susceptibility of said formation, and multiplying said null voltage by a factor derived from a function of said detected amplitude difference between said null voltage and said exciter voltage component of said receiver voltage.
Claim 17
Dependent Claim
36 words
The method described in claim 13, wherein said adjustment step further includes detecting the occurrence of any phase difference between said null and receiver voltages and realigning said null voltage into phase with said receiver voltage.
Claim 18
Dependent Claim
45 words
The method described in claim 14, wherein said phase correction step includes detecting the occurrence and magnitude of any phase differnce between said receiver voltage and said multiplied null voltage, and adjusting the phase of said null voltage in response to said phase monitoring means.
Claim 19
Independent Claim
125 words
A method for determining the magnetic susceptibility of a subsurface earth formation traversed by a borehole, comprising generating an AC exciter voltage, generating an electromagnetic field in said borehole and formation in response to said exciter voltage, deriving from said field a receiver voltage having components attributable to said exciter voltage and to the magnetic susceptibility of said formation, deriving a null voltage opposite in phase and at least substantially equal in magnitude to said exciter voltage component of said receiver voltage, deriving a difference voltage functionally related in magnitude to the difference amplitude between said null and receiver voltages, and maintaining a predetermined amplitude relationship between said null voltage anD said exciter voltage component of said receiver voltage in response to said difference voltage.
Claim 20
Independent Claim
125 words
A method for determining the magnetic susceptibility of a subsurface earth formation traversed by a borehole, comprising generating an AC exciter voltage, generating an electromagnetic field in said borehole and formation in response to said exciter voltage, deriving from said field a receiver voltage having components attributable to said exciter voltage and to the magnetic susceptibility of said formation, deriving a null voltage opposite in phase and at least substantially equal in magnitude to said exciter voltage component of said receiver voltage, deriving a difference voltage functionally related in magnitude to the difference amplitude between said null and receiver voltages, and maintaining a predetermined amplitude relationship between said null voltage anD said exciter voltage component of said receiver voltage in response to said difference voltage.
Claim 21
Dependent Claim
42 words
The method described in claim 16, wherein said maintaining further includes maintaining a predetermined phase relationship between said null and receiver voltages, and maintaining a predetermined amplitude relationship between said phase-regulated null voltage and said exciter voltage component of said receiver voltage.
Claim 22
Dependent Claim
47 words
The system described in claim 17, wherein said amplitude maintaining step further includes deriving a DC voltage functionally related to the amplitude difference between said exciter voltage and said difference voltage, and multiplying the amplitude of said phase-regulated null voltage by a function of said DC voltage.
Claim 23
Dependent Claim
67 words
The method described in claim 18, wherein said multiplying step further includes generating a function voltage having an amplitude functionally related to said DC voltage, providing an output voltage functionally related in amplitude to the product of the amplitudes of said function voltage and said phase-regulated null voltage, and deriving from said function voltage and said output voltage an amplitude-regulated null voltage component of said receiver voltage.
Claim 24
Dependent Claim
69 words
The method described in claim 19, wherein said phase maintaining step further includes deriving an AC phase measurement voltage functionally related in amplitude to any phase difference between said amplitude-regulated voltage and said exciter voltage, establishing a phase-shifting capacitance between said null inductance and said multiplier, and generating a control voltage to regulate the magnitude of said phase-shifting capacitance in functional relationship to the magnitude of said phase-measurement voltage.
References Cited (Backward Citations)
US3065407A
Cited
US3112443A
Cited
US3105190A
Cited
US3119061A
Cited
US3496455A
Cited
US3609522A
Cited
US3614600A
Cited
US3555409A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-09-10 | 1977-03-12 | 1977-09-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-09-10 | 1981-03-12 | 1981-09-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-09-10 | 1985-03-12 | 1985-09-11 | $7700.00 | Window Closed / Lapsed |