# US 7,612,567 B2 · Two-axial pad formation resistivity imager > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,612,567 B2 - Document ID: US7612567B2 - Status: Granted - Kind: B2 - Application number: 12/110,792 - Filed: 2008-04-28 - Published: 2008-11-13 - Granted: 2009-11-03 - Earliest claimed: 2005-12-29 - Assignees: Baker Hughes Incorporated - Inventors: Gregory B. Itskovich; Randy Gold; Alexandre N. Bespalov; Stanislav W. Forgang - Web page: https://patentgrep.com/patent/US7612567B2 ## CPC - G01V 3/24: using AC - G01V: GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS (means for indicating the location of accidentally buried, e.g. snow-buried, persons A63B29/02) ## Abstract A resistivity imaging device injects currents in two orthogonal directions using two pairs of return electrodes and performing impedance measurements of the buttons placed between the returns. ## Claims ### Claim 1 An apparatus for evaluating an earth formation penetrated by a borehole, the apparatus comprising: (a) a pad configured to be proximate to a wall of the borehole; (b) a first electrode disposed on the pad, the first electrode being configured to convey a current into the earth formation; (c) a return electrode horizontally displaced from the first electrode; and (d) a processor configured to: (A) select a frequency of the current using a resistivity of a borehole fluid and (II) a permittivity of the borehole fluid; (B) determine a resistivity property of the earth formation from the current in the first electrode and a voltage between the first electrode and the return electrode, and (C) record the resistivity property on a suitable medium. ### Claim 2 (depends on 1) The apparatus of claim 1 wherein the pad comprises a plurality of pads. ### Claim 3 (depends on 2) The apparatus of claim 2 wherein the processor is configured to determine at least one of: (I) a real part of an impedance, and (II) an imaginary part of the impedance. ### Claim 4 (depends on 2) The apparatus of claim 2 wherein the pad is extendable from a body of a logging tool. ### Claim 5 (depends on 2) The apparatus of claim 2 wherein the return electrode further comprises a pair of return electrodes. ### Claim 6 (depends on 1) The apparatus of claim 1 wherein the first electrode further comprises a plurality of current electrodes disposed azimuthally on the pad. ### Claim 7 (depends on 1) The apparatus of claim 1 wherein the determined resistivity property comprises a horizontal resistivity of the earth formation. ### Claim 8 (depends on 1) The apparatus of claim 1 further comprising an additional return electrode vertically separated from the first electrode; and wherein the processor determines from a current in the first electrode an additional property of the earth formation. ### Claim 9 (depends on 8) The apparatus of claim 8 wherein the return electrode further comprises an open-circuited pair of electrodes. ### Claim 10 (depends on 9) The apparatus of claim 9 wherein the additional property comprises a vertical resistivity of the earth formation. ### Claim 11 (depends on 1) The apparatus of claim 1 further comprising a logging tool configured to carry the pad, and a conveyance device which configured to convey the logging tool into the borehole. ### Claim 12 A method of evaluating an earth formation, the method comprising: (a) conveying a current into the earth formation using a pad-mounted current electrode proximate to a wall of a borehole in the formation a frequency of the current being selected using a resistivity of a borehole fluid and (II) a permittivity of the borehole fluid; (b) receiving the current in a return electrode horizontally separated from the current electrode; (c) determining a resistivity property of the earth formation from the current in the current electrode and a voltage between the current electrode and the return electrode; and (d) recording the determined resistivity property on a suitable medium. ### Claim 13 (depends on 12) The method of claim 12 further comprising using current electrodes on a plurality of pads. ### Claim 14 (depends on 13) The method of claim 13 wherein determining the resistivity further comprises determining at least one of: (I) a real part of an impedance, and (II) an imaginary part of the impedance. ### Claim 15 (depends on 13) The method of claim 13 further comprising positioning the plurality of current electrodes azimuthally on a pad. ### Claim 16 (depends on 13) The method of claim 13 wherein the determined resistivity property comprises a horizontal resistivity of the earth formation. ### Claim 17 (depends on 13) The method of claim 13 wherein the return electrode further comprises a first pair of return electrodes, the method further comprising: (i) open-circuiting the first pair of return electrodes, (ii) positioning a second pair of vertically separated return electrodes on the at least one pad; and (iii) determining from currents from the current electrodes an additional property of the earth formation. ### Claim 18 (depends on 17) The method of claim 17 wherein the additional property comprises a vertical resistivity of the earth formation. ### Claim 19 (depends on 18) The method of claim 18 further comprising selecting a frequency of the current using at least one of (i) a conductivity of a fluid in a borehole, and (ii) a permittivity of a fluid in a borehole. ### Claim 20 A computer readable medium for use with an apparatus for evaluating an earth formation penetrated by a borehole, the apparatus comprising: (a) at least one pad conveyed in a borehole the at least one pad proximate to a wall of the borehole; (b) at least one current electrode disposed on the at least one pad, the at least one current electrode configured to convey a current into the earth formation a frequency of the current being selected using a resistivity of a borehole fluid and (II) a permittivity of the borehole fluid; and (c) at least one return electrode horizontally displaced from the at least one current electrode; the medium comprising instructions that enable a processor to determine a resistivity property of the earth formation from the current in the at least one current electrode and a voltage between the at least one current electrode and the at least one return electrode. ### Claim 21 (depends on 20) The medium of claim 20 further comprising at least one of (i) a ROM, (ii) an EPROM, (iii) an EAROM, (iv) a flash memory, and (v) an optical disk.