Microresistivity anisotropy logging tool employing a monopole current injection electrode
First Claim
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1. downhole microresistivity logging tool comprising:
- a logging tool body;
a monopole current injection electrode configured to inject alternating electrical current into a formation;
a return electrode, the return electrode providine a return path for the electrical current injected by the monopole current injection electrode, the return electrode deployed in the tool body and spaced apart from the monopole current injection electrode;
a first pair of potential electrodes spaced apart from the monopole current injection electrode in a first direction;
a second pair of potential electrodes spaced apart from the monopole current injection electrode in a second direction; and
a controller configured to (i) apply an alternating current between the monopole current injection electrode and the return electrode and (ii) measure first and second potential differences between the corresponding first and second pairs of potential electrodes.
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Abstract
A microresistivity logging tool includes a monopole current injection electrode and at least first and second pairs of potential electrodes. The tool may further include a controller configured for making microresistivity anisotropy measurements using a single firing of the monopole current injection electrode. The controller may be configured to compute a two-dimensional tensor of the local formation resistivity from a single firing of the monopole current injection electrode. The use of a single firing tends to decrease measurement time, which in turn tends to improved azimuthal sensitivity in microresistivity anisotropy imaging while drilling applications.
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Citations
23 Claims
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1. downhole microresistivity logging tool comprising:
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a logging tool body; a monopole current injection electrode configured to inject alternating electrical current into a formation; a return electrode, the return electrode providine a return path for the electrical current injected by the monopole current injection electrode, the return electrode deployed in the tool body and spaced apart from the monopole current injection electrode; a first pair of potential electrodes spaced apart from the monopole current injection electrode in a first direction; a second pair of potential electrodes spaced apart from the monopole current injection electrode in a second direction; and a controller configured to (i) apply an alternating current between the monopole current injection electrode and the return electrode and (ii) measure first and second potential differences between the corresponding first and second pairs of potential electrodes. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A downhole microresistivity logging tool comprising:
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a logging tool body; a monopole current injection electrode configured to inject alternating electrical current into a formation; a return electrode, the return electrode providing a return path for the electrical current injected by the monopole current injection electrode, the return electrode deployed in the tool body and spaced apart from the monopole current injection electrode; a first array of potential electrodes spaced apart from the monopole current injection electrode in a first direction, the first array including at least first and second pairs of potential electrodes, the first pair of potential electrodes being, spaced apart from one another in the first direction and the second pair of potential electrodes being spaced apart from one another in the second direction; a second array of potential electrodes spaced apart from the monopole current injection electrode in the second direction, the second array including at least third and fourth pairs of potential electrodes, the third pair of potential electrodes being spaced apart from one another in the first direction and the fourth pair of potential electrodes being spaced apart from one another in the second direction; and a controller configured to (i) apply an alternating current between the monopole current injection electrode and the return electrode and (ii) substantially simultaneously make first, second, third, and fourth AC voltage measurements using the corresponding first, second, third, and fonrth pairs of potential electrodes. - View Dependent Claims (10, 11, 12, 13, 14)
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15. A method for making microresistivity anisotropy logging measurements, the method comprising;
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(a) deploying a microresistivity logging tool in a borehole, the logging tool including (i) a monopole current injection electrode, (ii) a return electrode, the return electrode providing a return path for electrical current injected by the monopole current injection electrode, the return electrode and the monopole current injection electrode being deployed in the tool body and spaced apart from one another; and
(iii), at least first and second pairs of potential electrodes, the first pair of potential electrodes being spaced apart from the monopole current injection electrode in a first direction and the second pair of potential electrodes being spaced apart from the monopole current injection electrode in a second direction;(b) causing an alternating electrical current to be injected into a subterranean formation at the monopole current injection electrode; (c) causing a first AC potential between the first pair of potential electrodes and a second AC potential between the second pair of potential electrodes to be measured substantially simultaneously; and (d) causing a processor to compute first and second resistivity values using the corresponding first and second AC potentials measured in (c). - View Dependent Claims (16, 17, 18)
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19. A method for making microresistivity anisotropy logging measurements, the method comprising:
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(a) deploying a microresistivity logging tool in a borehole, the logging tool including (i) a monopole current injection electrode, (ii) a return electrode, the return electrode providing a return path for electrical current injected by the monopole current injection electrode, the return electrode and the monopole current injection electrode being deployed in the tool body and spaced apart from one another; and
(iii), at least first, second, third, and fourth pairs of potential electrodes, the first and second pairs of potential electrodes being spaced apart from the monopole current injection electrode in a first direction and the third and fourth pairs of potential electrodes being spaced apart from the monopole current injection electrode in a second direction;(b) causing an alternating electrical current to be injected into a subterranean formation at the monopole current injection electrode; (c) causing first, second, third, and fourth AC potentials between the corresponding first, second, third, and fourth pairs of potential electrodes to be measured substantially simultaneously; (d) causing a processor to process the first, second, third, and fourth AC potentials measured in (c) to obtain a voltage tensor; and (e) causing a processor to compute a resistivity tensor from the voltage tensor obtained in (d). - View Dependent Claims (20, 21, 22, 23)
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Specification