Imaging Based on 4-Terminal Dual-Resistor Voltage Measurements
AssigneeBaker Hughes Incorporated
InventorsGregory B. Itskovich, Alexandre N. Bespalov
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Abstract
Measurements made by a four terminal resistivity imaging tool in a borehole using a voltage measurement device with two different input impedances. From the two measurements, formation resistivity is determined with minimal sensitivity to standoff. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.
Claims20
An apparatus for determining a resistivity parameter of an earth formation, the apparatus comprising:
- (a) a logging tool configured to be conveyed in a borehole in the earth formation;
- (b) a pair of current electrodes on the logging tool configured to convey a current into the formation;
- (c) at least one pair of voltage electrodes disposed between the pair of current electrodes;
- (d) at least one voltage measuring device connected to the at least one pair of voltage electrodes;
- and
- (e) a processor configured to:
- (A) determine the resistivity parameter of the earth formation using a first voltage measured at a first input impedance of the at least one voltage measuring device and a second voltage measured at a second input impedance of the at least one voltage measuring device, and
- (B) record the determined resistivity parameter on a suitable medium.
A method of determining a resistivity parameter of an earth formation, the method comprising:
- (a) conveying a logging tool into a borehole in the earth formation;
- (b) using a pair of current electrodes on the logging tool for conveying a current into the formation;
- (c) connecting at least one voltage measuring device to at least one pair of voltage electrodes disposed between the pair of current electrodes;
- (d) measuring a first voltage between the at least one pair of voltage electrodes at a first value of an input impedance of the at least one voltage measuring device;
- (e) measuring a second voltage between the at least one pair of voltage electrodes at a second value of an input impedance of the at least one voltage measuring device;
- (f) determining the resistivity parameter of the earth formation using the first voltage and the second voltage, and
- (g) recording the determined resistivity parameter on a suitable medium.
A computer-readable medium for use with an apparatus for determining a resistivity parameter of an earth formation, the apparatus comprising:
- (a) a logging tool configured to be conveyed in a borehole in the earth formation;
- (b) a pair of current electrodes on the logging tool configured to convey a current into the formation;
- (c) at least one pair of voltage electrodes positioned between the pair of current electrodes;
- and
- (d) at least one voltage measuring device connected to the at least one pair of voltage electrodes;
- the medium including instructions which enable a processor to:
- (e) determine the resistivity parameter of the earth formation using a first voltage measured at a first input impedance of the at least one voltage measuring device and a second voltage measured at a second input impedance of the at least one voltage measuring device, and
- (f) record the determined resistivity parameter on a suitable medium.
Dependencies are inferred from the claim text.