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US 4,583,046 AGranted
Apparatus for focused electrode induced polarization logging
AssigneeShell Oil Company
InventorsHarold J. Vinegar, Monroe H. Waxman
Life of this patent
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Abstract
An induced polarization tool using focused electrodes that uses direct coupling in the focusing loop to prevent spurious phase shifts. The invention uses a differential-in differential-out amplifier and voltage-controlled resistances to provide zero potential difference between pairs of monitoring electrodes. The measured current and voltage are digitized downhole and transmitted to the surface. At the surface means are provided for determining in-phase and quadrature response.
Claims20
An induced polarization logging tool comprising:
- an insulated logging sonde having at least a survey current electrode, upper and lower focusing electrodes placed equal distances on each side of said survey current electrode, upper and lower pairs of non-polarizing monitoring electrodes placed between the survey current and focusing electrodes on either side of said survey current electrode to generate signals to control the current supplied to the focusing electrodes, a non-polarizing voltage measurement electrode located between one pair of said monitoring electrodes, a non-polarizing voltage reference electrode and a current return electrode, both said voltage reference and current return electrodes being located a greater distance from said survey current electrode than said focusing electrodes;
- a differential-in differential-out amplifier, one monitoring electrode of each pair being direct coupled to one input of the amplifier, the other monitoring electrode of each pair being direct coupled to the other input of said amplifier;
- a first current control means, said survey current electrode being direct coupled to said first current control means through a reference resistor, the first output of said differential-in differential-out amplifier being direct coupled to said current control means to control the current flow to said survey electrode;
- a second current control means, said focusing electrodes being direct coupled to said second current control means, the second output of said differential-in differential-out amplifier being direct coupled to said second current control means to control the current flow to said focusing electrodes;
- a source of alternating current located at the surface, one end of said source being coupled to the two current control means and the other to the current return electrode, said source supplying alternating current at various discrete frequencies between substantially 0.01 and 100 Hz;
- first measurement means direct coupled to the voltage measurement and voltage reference electrodes to measure amplitude and phase of the voltage induced in the formation, and second measurement means direct coupled across the reference resistor to measure the amplitude and phase of the current flow to said survey current electrode;
- transmission means coupled to said first and second measurement means to transmit said voltage and current measurements to the surface;
- and
- means for converting said measured voltage and current to phase angle, formation resistivity, and spontaneous potential at the surface.
6 more elements
An induced polarization logging tool for measuring parameters of a formation surrounding a borehole, said logging tool comprising:
- a non-conductive logging sonde;
- a plurality of electrodes disposed on said sonde, said electrodes including at least a survey current electrode and two focusing electrodes disposed on opposite sides of said survey current electrode, non-polarizing monitoring electrodes disposed between the survey current electrode and each of said focusing electrodes to generate signals to control the current supplied to the focusing electrodes, a non-polarizing voltage measuring electrode, a non-polarizing voltage reference electrode and a current return electrode, both said voltage reference and current return electrodes being located a greater distance from said survey current electrode than said focusing electrodes;
- circuit means coupled to said monitoring electrodes for monitoring the potential difference in the formation adjacent thereto;
- first control means directly coupled to said survey current electrode and said circuit means for control of the current flow to said survey current electrode in response to the monitored potential difference;
- a second control means directly coupled to said focusing electrodes and said circuit means to control the current flow to said focusing electrodes in response to the monitored potential difference;
- a source of alternating current located at the surface, one end of said source being coupled to the two current control means and the other to the current return electrodes, said source supplying alternating current at various discrete frequencies between substantially 0.01 and 100 Hz;
- measurement means directly coupled to said voltage measurement and survey current electrodes to measure the amplitude and phase of the voltage induced in the formation and the amplitude and phase of the current flow to the survey current electrode;
- and
- transmission means for transmitting said measurements to the surface.
6 more elements
An induced polarization logging tool for measuring parameters of a formation surrounding a borehole, said logging tool comprising:
- a non-conductive logging sonde;
- a plurality of electrodes disposed on said sonde, said electrodes including at least a survey current electrode and guard electrodes disposed on opposite sides of said survey current electrode, a non-polarizing voltage measuring electrode, a non-polarizing voltage reference electrode and a current return electrode, both said voltage reference and current return electrodes being located a greater distance from said survey current electrode than said guard electrodes;
- means connected to said survey current electrode and said guard electrodes for generating a signal representative of the potential difference in the formation between said survey current electrode and said guard electrodes;
- first control means directly coupled to said survey current electrode, said first control means controlling the current flow to said survey current electrode in response to said potential difference signal;
- a second control means directly coupled to said guard electrodes to control the current flow to said guard electrodes in response to said potential difference signal;
- a source of alternating current located at the surface, one end of said source being coupled to the two control means and the other to the current return electrode, said source supplying alternating current at various discrete frequencies between substantially 0.01 and 100 Hz;
- measurement means directly coupled to said voltage measurement and survey current electrodes to measure the amplitude and phase of the voltage induced in the formation and the amplitude and phase of the current flow to the survey current electrode;
- and
- transmission means for transmitting said measurements to the surface.
6 more elements
Dependencies are inferred from the claim text.