US5001675A
Expired / Lapsed
US
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Phase and amplitude calibration system for electromagnetic propagation based earth formation evaluation instruments
Assignee: Baker Hughes Oilfield Operations LLC
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Filing: 1989-09-13
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Granted: 1991-03-19
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Expires: 2009-09-13
Abstract
Abstract A phase and amplitude calibration system for an electromagnetic propagation based earth formation evaluation tool is presented. In accordance with the present invention, improved phase and amplitude logs of a borehole section are provided by an automatic calibration system which compensates for errors caused by temperature and pressure variations in the borehole. This improvement is accomplished by applying in-phase, equal-amplitude reference signals to both measurement channels of a two channel system to thereby characterize system errors for correction of data used for logging. The reference signals are applied by tightly coupling a calibration signal to each receiving antenna. In a first embodiment, this is accomplished by adding a second antenna (a calibration antenna) to each of the two spaced receiving antennas. Each of the calibration antennas communicates with an attenuator which acts to make the calibration antenna transparent or invisible to the receiving antenna when the receiving antenna is in the measurement mode. The attenuator also sets the signal level delivered to the calibration antenna to a value that the receiving antenna would normally see in a measurement mode. In a second and preferred embodiment, the electrostatic shield surrounding each receiving antenna is used as a calibration antenna. The attenuator is then connected across the gap of the shield.
Inventors
- 👤 George H. Woodward
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 11:51
CPC Classifications
G; G01; G01V; G01V3/00; G01V3/18; G01V3/30; G01R; G01R35/00; G01R35/005; G01V13/00
Claims Analysis
Total Claims: 43
Claim 1
Independent Claim
100 words
A method of calibrating an electromagnetic propagation based earth formation evaluation instrument, the instrument including a drillstring segment having at least one transmitting antenna and at least one pair of spaced receiving antennas, including the steps of: tightly coupling calibration antenna means to each receiving antenna to define at least one pair of coupled calibration/receiving antennas; transmitting in-phase, equal-amplitude reference signals to each calibration receiving antenna; sensing the reference signals transmitted to said calibration/receiving antennas; delivering said sensed reference signals to microprocessor means; and calculating an error output from a comparison of the sensed reference signals using said microprocessor means.
Claim 2
Independent Claim
100 words
A method of calibrating an electromagnetic propagation based earth formation evaluation instrument, the instrument including a drillstring segment having at least one transmitting antenna and at least one pair of spaced receiving antennas, including the steps of: tightly coupling calibration antenna means to each receiving antenna to define at least one pair of coupled calibration/receiving antennas; transmitting in-phase, equal-amplitude reference signals to each calibration receiving antenna; sensing the reference signals transmitted to said calibration/receiving antennas; delivering said sensed reference signals to microprocessor means; and calculating an error output from a comparison of the sensed reference signals using said microprocessor means.
Claim 3
Dependent Claim
46 words
The method of claim 1 including: transmitting a measurement signal through the transmitting antenna; sensing the measurement signal through the pair of receiving antennas and calculating a formation evaluation output; and subtracting the error output from the formation evaluation output to define an error free output.
Claim 4
Dependent Claim
53 words
The method of claim 1 wherein the receiving antennas each comprise a first magnetic dipole antenna surrounded by an electrostatic shield and wherein said coupling step comprises: coupling a second magnetic dipole antenna to the first magnetic dipole antenna within the electrostatic shield, said second magnetic dipole antenna defining said calibration antenna means.
Claim 5
Dependent Claim
54 words
The method of claim 1 wherein the receiving antennas each comprise a first magnetic dipole antenna surrounded by an electrostatic shield, the shield including an insulated gap, and wherein said coupling step comprises: coupling the electrostatic shield across the insulated gap to the magnetic dipole antenna, said electrostatic shield defining said calibration antenna means.
Claim 6
Dependent Claim
34 words
The method of claim 1 including transmitting means for transmitting said reference signals and further including: electrically isolating said transmitting antenna from said transmitting means when transmitting said reference signals to each calibration/receiving antenna.
Claim 7
Dependent Claim
23 words
The method of claim 1 including: calibrating said electromagnetic propagation based earth formation evaluation instrument when said instrument is positioned in a borehole.
Claim 8
Dependent Claim
101 words
A calibration system for an electromagnetic propagation based earth formation evaluation instrument, the instrument including a drillstring segment having a transmitter normally connected to at least one transmitting antenna and at least one pair of spaced receiving antennas, comprising: calibration antenna means tightly coupled to each receiving antenna to define at least one pair of coupled calibration/receiving antennas; transmitting means for transmitting in-phase, equal-amplitude reference signals from the transmitter to each calibration/receiving antenna; sensing means for sensing the reference signals transmitted to the calibration/receiving antennas; and microprocessor means for calculating an error output from a comparison of the sensed reference signals.
Claim 9
Dependent Claim
101 words
A calibration system for an electromagnetic propagation based earth formation evaluation instrument, the instrument including a drillstring segment having a transmitter normally connected to at least one transmitting antenna and at least one pair of spaced receiving antennas, comprising: calibration antenna means tightly coupled to each receiving antenna to define at least one pair of coupled calibration/receiving antennas; transmitting means for transmitting in-phase, equal-amplitude reference signals from the transmitter to each calibration/receiving antenna; sensing means for sensing the reference signals transmitted to the calibration/receiving antennas; and microprocessor means for calculating an error output from a comparison of the sensed reference signals.
Claim 10
Dependent Claim
44 words
The system of claim 7 wherein the receiving antennas each comprise a first magnetic dipole antenna surrounded by an electrostatic sheath and wherein said calibration antenna means comprises: a second magnetic dipole antenna coupled to said first magnetic dipole antenna within the electrostatic sheath.
Claim 11
Dependent Claim
19 words
The system of claim 8 wherein: said first and second magnetic dipole antenna are configured as twisted pair wires.
Claim 12
Dependent Claim
18 words
The system of claim 8 wherein: said first and second magnetic dipole antennas are configured as ribbon cable.
Claim 13
Dependent Claim
18 words
The system of claim 8 wherein: said first and second magnetic dipole antennas are configured as coaxial cable.
Claim 14
Dependent Claim
56 words
The system of claim 7 wherein the receiving antennas each comprise a magnetic dipole antenna surrounded by an electrostatic sheath, the electrostatic sheath including an insulated gap and wherein: said calibration antenna means comprises said electrostatic sheath, said reference antenna means being coupled to said magnetic dipole means across the insulated gap of the electrostatic sheath.
Claim 15
Dependent Claim
12 words
The system of claim 7 wherein said transmitting means includes attenuator means.
Claim 16
Dependent Claim
44 words
The system of claim 13 wherein said attenuator means comprises: first and second resistors having substantially the same value; and a third resistor connected to said first and second resistors, said third resistor having a lower value relative to said first and second resistors.
Claim 17
Dependent Claim
44 words
The system of claim 14 wherein an electrostatic sheath surrounds the receiving antenna, the electrostatic sheath including a gap having an insulator in said gap, and wherein: said first, second and third resistors comprise discrete chip or film resistors attached to said gap insulator.
Claim 18
Dependent Claim
28 words
The system of claim 14 wherein: said first and second resistors have values of about 10,000 Ohm; and said third resistor has a value of about 100 Ohm.
Claim 19
Dependent Claim
42 words
The system of claim 14 wherein: said first and second resistors are connected in series to said calibration antenna means; and said third resistor is connected in parallel to a transmission line, said transmission line being connected to said calibration antenna means.
Claim 20
Dependent Claim
19 words
The system of claim 7 including: means for switching the transmitter between a measurement mode and a calibration mode.
Claim 21
Dependent Claim
16 words
The system of claim 7 including: means for subtracting said error output from formation evaluation output.
Claim 22
Dependent Claim
26 words
The system of claim 7 including: means for electrically isolating said transmitting antenna from said transmitting means when transmitting said reference signals to each calibration/receiving antenna.
Claim 23
Dependent Claim
20 words
The system of claim 7 including: said calibration system is integral to said electromagnetic propagation based earth formation evaluation tool.
Claim 24
Independent Claim
81 words
A method of calibrating an electromagnetic propagation based earth formation evaluation instrument, the instrument including a drillstring segment having at least one transmitting antenna and at least one pair of spaced receiving antennas, including the steps of: tightly coupling a calibration signal to each receiving antenna to define in-phase, equal-amplitude reference signals; sensing the reference signals; delivering said sensed reference signals to microprocessor means; and calculating an error output from a comparison of the sensed reference signals using said microprocessor means.
Claim 25
Independent Claim
81 words
A method of calibrating an electromagnetic propagation based earth formation evaluation instrument, the instrument including a drillstring segment having at least one transmitting antenna and at least one pair of spaced receiving antennas, including the steps of: tightly coupling a calibration signal to each receiving antenna to define in-phase, equal-amplitude reference signals; sensing the reference signals; delivering said sensed reference signals to microprocessor means; and calculating an error output from a comparison of the sensed reference signals using said microprocessor means.
Claim 26
Dependent Claim
34 words
The method of claim 22 including transmitting means for transmitting said reference signals and further including: electrically isolating said transmitting antenna from said transmitting means when transmitting said reference signals to each calibration/receiving antenna.
Claim 27
Dependent Claim
23 words
The method of claim 22 including: calibrating said electromagnetic propagation based earth formation evaluation instrument when said instrument is positioned in a borehole.
Claim 28
Independent Claim
77 words
A system of calibrating an electromagnetic propagation based earth formation evaluation instrument, the instrument including a drillstring segment having at least one transmitting antenna and at least one pair of spaced receiving antennas, including the steps of: means for tightly coupling a reference signal to each receiving antenna to define in-phase, equal-amplitude reference signals; sensing means for sensing the reference signals; and microprocessor means for calculating an error output from a comparison of the sensed reference signals.
Claim 29
Independent Claim
77 words
A system of calibrating an electromagnetic propagation based earth formation evaluation instrument, the instrument including a drillstring segment having at least one transmitting antenna and at least one pair of spaced receiving antennas, including the steps of: means for tightly coupling a reference signal to each receiving antenna to define in-phase, equal-amplitude reference signals; sensing means for sensing the reference signals; and microprocessor means for calculating an error output from a comparison of the sensed reference signals.
Claim 30
Dependent Claim
26 words
The system of claim 25 including: means for electrically isolating said transmitting antenna from said transmitting means when transmitting said reference signals to each calibration/receiving antenna.
Claim 31
Dependent Claim
20 words
The system of claim 25 wherein: said calibration system is integral to said electromagnetic propagation based earth formation evaluation tool.
Claim 32
Independent Claim
107 words
A method of calibrating an electromagnetic propagation based earth formation evaluation instrument, the instrument including a drillstring segment having at least one transmitting antenna and at least one pair of spaced receiving antennas, including the steps of: tightly coupling calibration antenna means to each receiving antenna to define at least one pair of coupled calibration/receiving antennas; transmitting reference signals to each calibration/receiving antennas, said reference signals having known pre-selected phase and amplitude relationships; sensing the reference signals transmitted to said calibration/receiving antennas; delivering said sensed reference signals to microprocessor means; and calculating an error output from a comparison of the sensed reference signals using said microprocessor means.
Claim 33
Independent Claim
107 words
A method of calibrating an electromagnetic propagation based earth formation evaluation instrument, the instrument including a drillstring segment having at least one transmitting antenna and at least one pair of spaced receiving antennas, including the steps of: tightly coupling calibration antenna means to each receiving antenna to define at least one pair of coupled calibration/receiving antennas; transmitting reference signals to each calibration/receiving antennas, said reference signals having known pre-selected phase and amplitude relationships; sensing the reference signals transmitted to said calibration/receiving antennas; delivering said sensed reference signals to microprocessor means; and calculating an error output from a comparison of the sensed reference signals using said microprocessor means.
Claim 34
Dependent Claim
16 words
The method of claim 28 wherein: said known phase and amplitude relationships comprise in-phase, equal-amplitude relationships.
Claim 35
Dependent Claim
111 words
A calibration system for an electromagnetic propagation based earth formation evaluation instrument, the instrument including a drillstring segment having a transmitter normally connected to at least one transmitting antenna and at least one pair of spaced receiving antennas, comprising: calibration antenna means tightly coupled to each receiving antenna to define at least one pair of coupled calibration/receiving antennas; transmitting means for transmitting reference signals from the transmitter to each calibration receiving antenna, said reference signals having known pre-selected phase and amplitude relationships; and sensing means for sensing the reference signals transmitted to the calibration/receiving antennas; and microprocessor means for calculating an error output from a comparison of the sensed reference signals.
Claim 36
Dependent Claim
111 words
A calibration system for an electromagnetic propagation based earth formation evaluation instrument, the instrument including a drillstring segment having a transmitter normally connected to at least one transmitting antenna and at least one pair of spaced receiving antennas, comprising: calibration antenna means tightly coupled to each receiving antenna to define at least one pair of coupled calibration/receiving antennas; transmitting means for transmitting reference signals from the transmitter to each calibration receiving antenna, said reference signals having known pre-selected phase and amplitude relationships; and sensing means for sensing the reference signals transmitted to the calibration/receiving antennas; and microprocessor means for calculating an error output from a comparison of the sensed reference signals.
Claim 37
Dependent Claim
16 words
The method of claim 30 wherein: said known phase and amplitude relationships comprise in-phase, equal-amplitude relationships.
Claim 38
Independent Claim
84 words
A method of calibrating an electromagnetic propagation based earth formation evaluation instrument, the instrument including a drillstring segment having at least one transmitting antenna and at least one pair of spaced receiving antennas, including the steps of: tightly coupling a reference signal to each receiving antenna to define reference signals having known pre-selected phase and amplitude relationships; sensing the reference signals; and delivering said sensed reference signals to microprocessor means; and calculating an error output from the sensed reference signals using said microprocessor means.
Claim 39
Independent Claim
84 words
A method of calibrating an electromagnetic propagation based earth formation evaluation instrument, the instrument including a drillstring segment having at least one transmitting antenna and at least one pair of spaced receiving antennas, including the steps of: tightly coupling a reference signal to each receiving antenna to define reference signals having known pre-selected phase and amplitude relationships; sensing the reference signals; and delivering said sensed reference signals to microprocessor means; and calculating an error output from the sensed reference signals using said microprocessor means.
Claim 40
Dependent Claim
16 words
The method of claim 32 wherein: said known phase and amplitude relationships comprise in-phase, equal-amplitude relationships.
Claim 41
Independent Claim
82 words
A system of calibrating an electromagnetic propagation based earth formation evaluation instrument, the instrument including a drillstring segment having at least one transmitting antenna and at least one pair of spaced receiving antennas, including the steps of: means for tightly coupling a reference signal to each receiving antenna to define reference signals having known pre-selected phase and amplitude relationships; sensing means for sensing the reference signals; and microprocessor means for calculating an error output from a comparison of the sensed reference signal.
Claim 42
Independent Claim
82 words
A system of calibrating an electromagnetic propagation based earth formation evaluation instrument, the instrument including a drillstring segment having at least one transmitting antenna and at least one pair of spaced receiving antennas, including the steps of: means for tightly coupling a reference signal to each receiving antenna to define reference signals having known pre-selected phase and amplitude relationships; sensing means for sensing the reference signals; and microprocessor means for calculating an error output from a comparison of the sensed reference signal.
Claim 43
Dependent Claim
16 words
The method of claim 34 wherein: said known phase and amplitude relationships comprise in-phase, equal-amplitude relationships.
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) | 1994-03-18 | 1994-09-17 | 1995-03-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-03-18 | 1998-09-17 | 1999-03-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-03-18 | 2002-09-17 | 2003-03-19 | $7700.00 | Window Closed / Lapsed |