High resolution resistivity earth imager
AssigneeBaker Hughes Incorporated
InventorsAlexandre N. Bespalov, Gregory B. Itskovich
Life of this patent
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Abstract
Phase-sensitive measurements are made by a resistivity imaging tool in a borehole having non-conductive mud in a conductive earth formation at a plurality of frequencies. From the phase sensitive measurements, the formation resistivity can be determined with higher sensitivity than is possible with the single frequency measurements. Tool standoff can also be determined from a knowledge of the mud resistivity and/or dielectric constant. Formation resistivity may also be determined when the effect of formation capacitance cannot be ignored.
Claims24
An apparatus for evaluating an earth formation penetrated by a borehole, the apparatus comprising:
- (a) at least one measure electrode coupled to a source of electrical current, the at least one measure electrode configured to convey a measure current into the formation at a plurality of frequencies;
- and
- (b) a processor which is configured to estimate a resistivity parameter of the earth formation based at least in part on a real part and an imaginary part of an impedance at the at least one measure electrode at each of the plurality of frequencies.
A method of evaluating an earth formation penetrated by a borehole, the method comprising:
- (a) using at least one measure electrode coupled to a source of electrical current for conveying a measure current into the formation at a plurality of frequencies, the at least one measure electrode having a potential;
- and
- (b) estimating a resistivity parameter of the earth formation based at least in part on a real part and an imaginary part of an impedance determined from the measure current at each of the plurality of frequencies.
The method of 13 further comprising disposing a plurality of measure electrodes on a pad extendable from a body of a logging tool conveyed in the borehole.
A computer readable medium for use with an apparatus used for evaluating an earth formation penetrated by a borehole, the apparatus comprising:
- (a) at least one measure electrode connected to a source of electrical current and conveying a measure current into the formation at a plurality of frequencies;
- the medium comprising instructions which enable:
- (b) a processor to estimate a resistivity parameter of the earth formation based at least in part on a real and imaginary part of an impedance determined at the plurality of frequencies.
Dependencies are inferred from the claim text.