US3601692A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Electrical logging system utilizing impedance means between survey and measure electrodes
Assignee: Schlumberger Technology Corp
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Filing: 1969-05-15
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Granted: 1971-08-24
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Expires: 1989-05-15
Abstract
Abstract In accordance with illustrative embodiments of the present invention, a well tool having wall-engaging pad members is moved through a borehole. Current is supplied to a current electrode A on each pad member and the resulting potential on a nearby electrode M on each pad member is measured to provide a measure of formation resistivity. A shunt resistor is connected between the A- and M-electrodes of each pad member and has a resistance value suitable to enable the system to provide reasonably accurate measurements when the A- and/or M-electrodes fail to make reasonably good electrical contact with the formation. However, when the contact resistance between the A- and Melectrodes is so bad that genuine resistivity measurements cannot be made, the measuring system will produce very high, off-scale measurement values to indicate such an occurrence. In another embodiment of the invention, the electrodes are energized with current at a plurality of frequencies to enable separate measurements to be made. These measurements when utilized in a desirable manner, can enable a relatively authentic resistivity measurement to be obtained.
Inventors
- 👤 Nick A Schuster
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 17:52
CPC Classifications
G; G01; G01V; G01V3/00; G01V3/18; G01V3/20; G01V3/24
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
120 words
Apparatus for use in investigating subsurface earth formations traversed by a borehole, comprising: a plurality of electrodes adapted for movement through a borehole; means for supplying current between first and second ones of said electrodes for emission into an earth formation; means for measuring the potential on a third one of said electrodes located near said first electrode to provide a measure of the resistance of a formation portion; and an impedance element having one end connected to said first electrode and the other end connected to said third electrode for providing a current path through said impedance element to said third electrode and said measuring means, the impedance of said impedance element being substantially greater than said formation resistance.
Claim 2
Dependent Claim
120 words
Apparatus for use in investigating subsurface earth formations traversed by a borehole, comprising: a plurality of electrodes adapted for movement through a borehole; means for supplying current between first and second ones of said electrodes for emission into an earth formation; means for measuring the potential on a third one of said electrodes located near said first electrode to provide a measure of the resistance of a formation portion; and an impedance element having one end connected to said first electrode and the other end connected to said third electrode for providing a current path through said impedance element to said third electrode and said measuring means, the impedance of said impedance element being substantially greater than said formation resistance.
Claim 3
Dependent Claim
142 words
Apparatus for investigating subsurface earth formations traversed by a borehole, comprising: a plurality of electrodes adapted for movement through a borehole; means for supplying current between first and second ones of said electrodes for emission into an earth formation; means for measuring the potential on a third one of said electrodes located near said first electrode to provide a measure of the resistance of a formation portion; and an impedance element having one end connected to said first electrode and the other end connected to said third electrode for providing relatively significant amounts of the current through said impedance element to said measuring means or said third electrode for emission into a formation whenever said first and/or third electrode does not make reasonably good electrical contact with a formation, the impedance of said impedance element being substantially greater than said formation resistance.
Claim 4
Dependent Claim
142 words
Apparatus for investigating subsurface earth formations traversed by a borehole, comprising: a plurality of electrodes adapted for movement through a borehole; means for supplying current between first and second ones of said electrodes for emission into an earth formation; means for measuring the potential on a third one of said electrodes located near said first electrode to provide a measure of the resistance of a formation portion; and an impedance element having one end connected to said first electrode and the other end connected to said third electrode for providing relatively significant amounts of the current through said impedance element to said measuring means or said third electrode for emission into a formation whenever said first and/or third electrode does not make reasonably good electrical contact with a formation, the impedance of said impedance element being substantially greater than said formation resistance.
Claim 5
Dependent Claim
158 words
Apparatus for investigating subsurface earth formations traversed by a borehole, comprising: means for carrying at least one wall-engaging pad member for passage through a borehole; a plurality of electrodes, at least some of said electrodes being mounted on the borehole wall-engaging face of said pad member; means for supplying current to a first one of said pad-mounted electrodes for emission into an earth formation, said emitted current returning to a remote location for return to said current-supplying means; means for measuring the potential on a second one of said pad-mounted electrodes, located near said first electrode to provide a measure of the resistance of a formation portion; and an impedance element having one end connected to said first electrode and the other end connected to said second electrode for providing a current path through said impedance element to said measuring means and said second electrode, the impedance of said impedance element being substantially greater than said formation resistance.
Claim 6
Dependent Claim
158 words
Apparatus for investigating subsurface earth formations traversed by a borehole, comprising: means for carrying at least one wall-engaging pad member for passage through a borehole; a plurality of electrodes, at least some of said electrodes being mounted on the borehole wall-engaging face of said pad member; means for supplying current to a first one of said pad-mounted electrodes for emission into an earth formation, said emitted current returning to a remote location for return to said current-supplying means; means for measuring the potential on a second one of said pad-mounted electrodes, located near said first electrode to provide a measure of the resistance of a formation portion; and an impedance element having one end connected to said first electrode and the other end connected to said second electrode for providing a current path through said impedance element to said measuring means and said second electrode, the impedance of said impedance element being substantially greater than said formation resistance.
Claim 7
Dependent Claim
186 words
Apparatus for investigating subsurface earth formations traversed by a borehole, comprising: means for carrying at least one wall-engaging pad member for passage through a borehole; a plurality of electrodes, at least some of said electrodes being mounted on the borehole wall-engaging face of said pad member; means for suppLying current to a first one of said pad-mounted electrodes for emission into an earth formation, said emitted current returning to a remote location for return to said current-supplying means; means for measuring the potential on a second one of said pad-mounted electrodes located near said first electrode to provide a measure of a formation characteristic; and a resistor connected between said first and second electrodes and having a suitable resistance value to provide a significant amount of current through said second electrode to a formation whenever said first electrode does not make reasonably good electrical contact with a formation and for providing a significant amount of current to said measuring means from said current supply means whenever said second electrode alone or both of said electrodes together do not make reasonably good electrical contact with a formation.
Claim 8
Dependent Claim
186 words
Apparatus for investigating subsurface earth formations traversed by a borehole, comprising: means for carrying at least one wall-engaging pad member for passage through a borehole; a plurality of electrodes, at least some of said electrodes being mounted on the borehole wall-engaging face of said pad member; means for suppLying current to a first one of said pad-mounted electrodes for emission into an earth formation, said emitted current returning to a remote location for return to said current-supplying means; means for measuring the potential on a second one of said pad-mounted electrodes located near said first electrode to provide a measure of a formation characteristic; and a resistor connected between said first and second electrodes and having a suitable resistance value to provide a significant amount of current through said second electrode to a formation whenever said first electrode does not make reasonably good electrical contact with a formation and for providing a significant amount of current to said measuring means from said current supply means whenever said second electrode alone or both of said electrodes together do not make reasonably good electrical contact with a formation.
Claim 9
Dependent Claim
199 words
Apparatus for investigating subsurface earth formations traversed by a borehole, comprising: means for carrying a plurality of wall-engaging pad members for passage through a borehole; a plurality of electrodes, at least some of which are mounted on the borehole wall-engaging faces of said pad members; means for supplying current to a first electrode on each pad member for emission into an earth formation adjoining each pad member; separate means associated with each pad member for measuring the potential on a second electrode located near said first electrode on each pad member to provide individual measurements of a formation characteristic; and impedance means connected between said first and second electrodes on each pad member for providing a significant amount of current through said second electrode on each pad member to a formation whenever said first electrode on each pad member does not make reasonably good electrical contact with a formation and for providing a significant amount of current from said current supply means to said measuring means associated with each pad member whenever either said second electrode alone or both said first and second electrodes together of each pad member do not make reasonably good electrical contact with a formation.
Claim 10
Dependent Claim
199 words
Apparatus for investigating subsurface earth formations traversed by a borehole, comprising: means for carrying a plurality of wall-engaging pad members for passage through a borehole; a plurality of electrodes, at least some of which are mounted on the borehole wall-engaging faces of said pad members; means for supplying current to a first electrode on each pad member for emission into an earth formation adjoining each pad member; separate means associated with each pad member for measuring the potential on a second electrode located near said first electrode on each pad member to provide individual measurements of a formation characteristic; and impedance means connected between said first and second electrodes on each pad member for providing a significant amount of current through said second electrode on each pad member to a formation whenever said first electrode on each pad member does not make reasonably good electrical contact with a formation and for providing a significant amount of current from said current supply means to said measuring means associated with each pad member whenever either said second electrode alone or both said first and second electrodes together of each pad member do not make reasonably good electrical contact with a formation.
Claim 11
Dependent Claim
168 words
Apparatus for investigating subsurface earth formations traversed by a borehole, comprising: means for carrying at least one wall-engaging pad member for passage through a borehole; a plurality of electrodes, at least some of said electrodes being mounted on the borehole wall-engaging face of said pad member; means for supplying current to a first pad-mounted electrode for emission into an earth formation, said emitted current returning to a return electrode; means for measuring the potential difference between a second pad-mounted electrode located near said first electrode and a relatively remote point to provide a measure of the resistance of a formation portion; and an impedance element having one end connected to said first electrode and the other end connected to said second electrode for providing a current path through said impedance element to said measuring means and/or said second electrode whenever said first and/or second electrode does not make reasonably good electrical contact with a formation, the impedance of said impedance element being substantially greater than said formation resistance.
Claim 12
Dependent Claim
168 words
Apparatus for investigating subsurface earth formations traversed by a borehole, comprising: means for carrying at least one wall-engaging pad member for passage through a borehole; a plurality of electrodes, at least some of said electrodes being mounted on the borehole wall-engaging face of said pad member; means for supplying current to a first pad-mounted electrode for emission into an earth formation, said emitted current returning to a return electrode; means for measuring the potential difference between a second pad-mounted electrode located near said first electrode and a relatively remote point to provide a measure of the resistance of a formation portion; and an impedance element having one end connected to said first electrode and the other end connected to said second electrode for providing a current path through said impedance element to said measuring means and/or said second electrode whenever said first and/or second electrode does not make reasonably good electrical contact with a formation, the impedance of said impedance element being substantially greater than said formation resistance.
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) | 1974-08-23 | 1975-02-22 | 1975-08-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-08-23 | 1979-02-22 | 1979-08-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-08-23 | 1983-02-22 | 1983-08-24 | $7700.00 | Window Closed / Lapsed |