Patent US1857475A successfully refreshed from Google Patents.
US3798534A
Expired / Lapsed
US
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Methods and apparatus for investigating earth formations
Assignee: Schlumberger Technology Corp
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Filing: 1972-04-24
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Granted: 1974-03-19
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Expires: 1992-04-24
Abstract
Abstract In accordance with illustrative embodiments of the present invention, an electrode array is utilized for investigating earth formations surrounding a mud filled borehole without undue influence from a conductive mud column. One manner of accomplishing this is to establish a potential distribution in the borehole as if the mud column were of the same resistivity as the formation. Alternatively, a zero potential gradient can be established at various regions in the mud column to effectively block current flow up or down the mud column.
Inventors
- 👤 N Schuster
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 04:37
CPC Classifications
G; G01; G01V; G01V3/00; G01V3/18; G01V3/20; G01V3/24
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
226 words
AppAratus for measuring a characteristic of earth formations traversed by a borehole, comprising: a plurality of electrodes including at least one currentemitting electrode, a pair of measuring electrodes located on each side of said at least one current-emitting electrode, first current electrodes including a pair of electrodes with one each located between each of said measuring electrode pairs and said at least one current-emitting electrode, and a second current return electrode spaced apart from said first current return electrodes; means for mounting said electrodes for passage through a borehole; means responsive to the potential difference between the potentials of said measuring electrode pairs for supplying a first current between said at least one current-emitting electrode and one of said first or second current return electrodes of sufficient magnitude to maintain said potential difference at a substantially constant value; means responsive to a second potential difference between a potential at a first point lying between said first current return electrodes and a potential at a second point between said measuring electrodes for supplying a second current between said at least one current-emitting electrode and the other of said first or second current return electrodes of sufficient magnitude to maintain said second potential difference at a substantially constant level; and means responsive to one of said first or second currents for obtaining a measure of a formation characteristic.
Claim 2
Dependent Claim
226 words
AppAratus for measuring a characteristic of earth formations traversed by a borehole, comprising: a plurality of electrodes including at least one currentemitting electrode, a pair of measuring electrodes located on each side of said at least one current-emitting electrode, first current electrodes including a pair of electrodes with one each located between each of said measuring electrode pairs and said at least one current-emitting electrode, and a second current return electrode spaced apart from said first current return electrodes; means for mounting said electrodes for passage through a borehole; means responsive to the potential difference between the potentials of said measuring electrode pairs for supplying a first current between said at least one current-emitting electrode and one of said first or second current return electrodes of sufficient magnitude to maintain said potential difference at a substantially constant value; means responsive to a second potential difference between a potential at a first point lying between said first current return electrodes and a potential at a second point between said measuring electrodes for supplying a second current between said at least one current-emitting electrode and the other of said first or second current return electrodes of sufficient magnitude to maintain said second potential difference at a substantially constant level; and means responsive to one of said first or second currents for obtaining a measure of a formation characteristic.
Claim 3
Dependent Claim
224 words
Apparatus for measuring a characteristic of earth formations traversed by a borehole, comprising: a plurality of electrodes including at least one current-emitting electrode, a pair of measuring electrodes located on each side of said at least one current-emitting electrodes, auxiliary current return electrodes located between each of said measuring electrode pairs and said at least one current-emitting electrode, auxiliary measuring electrodes with one each located between said at least one current-emitting electrode and each of said auxiliary current return electrodes, and a survey current return electrode spaced apart from all of said other electrodes; means for mounting said electrodes for passage through a borehole; means responsive to the potential difference between the potentials of said measuring electrode pairs for supplying a survey current between said at least one current-emitting electrode and said survey current return electrode of sufficient magnitude to maintain said potential difference at a substantially fixed value; means responsive to a second potential difference between the potential of said auxiliary measuring electrodes and a potential of a point lying between said measuring electrodes for supplying an auxiliary current between said at least one current-emitting electrode and said auxiliary current return electrodes of sufficient magnitude to maintain said second potential difference at a substantially constant level; and means responsive to said survey current for obtaining a measure of the conductivity of a formation.
Claim 4
Dependent Claim
224 words
Apparatus for measuring a characteristic of earth formations traversed by a borehole, comprising: a plurality of electrodes including at least one current-emitting electrode, a pair of measuring electrodes located on each side of said at least one current-emitting electrodes, auxiliary current return electrodes located between each of said measuring electrode pairs and said at least one current-emitting electrode, auxiliary measuring electrodes with one each located between said at least one current-emitting electrode and each of said auxiliary current return electrodes, and a survey current return electrode spaced apart from all of said other electrodes; means for mounting said electrodes for passage through a borehole; means responsive to the potential difference between the potentials of said measuring electrode pairs for supplying a survey current between said at least one current-emitting electrode and said survey current return electrode of sufficient magnitude to maintain said potential difference at a substantially fixed value; means responsive to a second potential difference between the potential of said auxiliary measuring electrodes and a potential of a point lying between said measuring electrodes for supplying an auxiliary current between said at least one current-emitting electrode and said auxiliary current return electrodes of sufficient magnitude to maintain said second potential difference at a substantially constant level; and means responsive to said survey current for obtaining a measure of the conductivity of a formation.
Claim 5
Independent Claim
224 words
A method of measuring a characteristic of earth formations traversed by a borehole, comprising: carrying a plurality of electrodes through a borehole, said electrodes including at least one current-emitting electrode, a pair of measuring electrodes located on each side of said at least one current-emitting electrode, first current return electrodes including a pair of electrodes with one each located between each of said measuring electrode pairs and said at least one current-emitting electrode, and a second current return electrode spaced apart from said first current return electrodes; measuring the potential difference between the potentials of said measuring electrode pairs; supplying a first current between said at least one current-emitting electrode and one of said first or second current return electrodes in response to said measured potential difference to maintaiN said potential difference at a substantially constant value; measuring a second potential difference between a potential at a point lying between said first current return electrodes and a potential of a point lying between said measuring electrodes; supplying a second current between said at least one current-emitting electrode and the other of said first or second current return electrodes in response to said second measured potential difference to maintain said second potential difference at a substantially constant level; and measuring one of said first or second currents to obtain an indication of a formation characteristic.
Claim 6
Independent Claim
224 words
A method of measuring a characteristic of earth formations traversed by a borehole, comprising: carrying a plurality of electrodes through a borehole, said electrodes including at least one current-emitting electrode, a pair of measuring electrodes located on each side of said at least one current-emitting electrode, first current return electrodes including a pair of electrodes with one each located between each of said measuring electrode pairs and said at least one current-emitting electrode, and a second current return electrode spaced apart from said first current return electrodes; measuring the potential difference between the potentials of said measuring electrode pairs; supplying a first current between said at least one current-emitting electrode and one of said first or second current return electrodes in response to said measured potential difference to maintaiN said potential difference at a substantially constant value; measuring a second potential difference between a potential at a point lying between said first current return electrodes and a potential of a point lying between said measuring electrodes; supplying a second current between said at least one current-emitting electrode and the other of said first or second current return electrodes in response to said second measured potential difference to maintain said second potential difference at a substantially constant level; and measuring one of said first or second currents to obtain an indication of a formation characteristic.
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) | 1977-03-18 | 1977-09-17 | 1978-03-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-03-18 | 1981-09-17 | 1982-03-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-03-18 | 1985-09-17 | 1986-03-19 | $7700.00 | Window Closed / Lapsed |