# US 2017/0285212 A1 · System and method for measuring downhole parameters > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2017/0285212 A1 - Document ID: US20170285212A1 - Status: Published application - Kind: A1 - Application number: 15/468,177 - Filed: 2017-03-24 - Published: 2017-10-05 - Earliest claimed: 2016-04-01 - Assignees: Schlumberger Technology Corporation - Applicants: Schlumberger Technology Corporation - Inventors: Richard Bloemenkamp - Web page: https://patentgrep.com/patent/US20170285212A1 ## CPC - E21B 49/00: Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells - E21B 47/01: Devices for supporting measuring instruments on drill bits, pipes, rods or wirelines; Protecting measuring instruments in boreholes against heat, shock, pressure or the like - G01V 3/24: using AC - E21B 47/12: Means for transmitting measuring-signals or control signals from the well to the surface, or from the surface to the well, e.g. for logging while drilling - E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS - 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 An apparatus and method for making resistivity measurements of an underground formation surrounding a borehole is disclosed. The apparatus includes a conductive tool body section. The apparatus includes an electrically decoupling insulated tool body section mechanically coupled to the conductive tool body section. The apparatus includes a conductive current return (CR) tool body section mechanically coupled to the electrically decoupling insulated tool body section. The apparatus includes a pad mounted on the conductive tool body section that injects current into the formation at a frequency in a range above 100 kHz and below 10 MHz. The pad includes at least one button electrode that measures current injected into the formation. The pad also includes a standoff spacer affixed to the conductive plate configured for direct contact with the formation. The apparatus includes extendable suspension means affixed to the conductive plate, that, when extended, cause direct contact between the standoff spacer and the formation. ## Claims ### Claim 1 An apparatus for making resistivity measurements of an underground formation surrounding a borehole, comprising: a conductive tool body section; an electrically decoupling insulated tool body section mechanically coupled to the conductive tool body section; a conductive current return (CR) tool body section mechanically coupled to the electrically decoupling insulated tool body section, the conductive CR tool body section configured for direct contact with the formation; a pad 116 mounted on the conductive tool body section, wherein the pad comprises: a conductive plate that injects current into the formation at a frequency in a range above 100 kHz and below 10 MHz; at least one button electrode that measures current injected into the formation; and a standoff spacer affixed to the conductive plate, the standoff spacer configured for direct contact with the formation; and extendable suspension means affixed to the conductive plate, that, when extended, cause direct contact between the standoff spacer and the formation. ### Claim 2 (depends on 1) The apparatus of claim 1, wherein the standoff spacer provides a minimum standoff between the borehole wall and the pad. ### Claim 3 (depends on 1) The apparatus of claim 1, wherein portions of the standoff spacer comprise a tungsten carbide material coating. ### Claim 4 (depends on 1) The apparatus of claim 1, wherein portions of the standoff spacer comprise a PEEK material having a thickness of around 1 mm or more. ### Claim 5 (depends on 1) The apparatus of claim 1, wherein thickness or material of standoff spacer is selected as a function of geometry and size of the pad and smoothness of the borehole. ### Claim 6 (depends on 1) The apparatus of claim 1, wherein the standoff spacer further comprises insulation affixed to the borehole-facing side of the conductive plate and a wear plate affixed to the borehole-facing side of the insulation. ### Claim 7 (depends on 1) The apparatus of claim 1, further comprising a signal source connected between the conductive tool body section and the conductive CR tool body section and operable to generate an injection current. ### Claim 8 (depends on 1) The apparatus of claim 1, wherein the conductive CR tool body section is a mandrel of the downhole tool. ### Claim 9 (depends on 1) The apparatus of claim 1, further comprising signal processing means for generating a resistivity image of the wall of the borehole based on current measured at conductive CR tool body section. ### Claim 10 (depends on 6) The apparatus of claim 6, the insulation having impedance of above 10 Ohms in an oil based mud. ### Claim 11 (depends on 1) The apparatus of claim 1, wherein the extendable suspension means affixing the pad to the conductive tool body section further comprises insulation. ### Claim 12 (depends on 1) The apparatus of claim 1, comprising an additional sensor affixed to tool body section of downhole tool to measure borehole wave propagation. ### Claim 13 (depends on 1) The apparatus of claim 1, wherein the conductive plate injects current into the formation at a frequency above 1 MHz. ### Claim 14 A method for measuring downhole parameters of an underground formation, the underground formation having a wellbore extending therethrough, the method comprising: deploying the downhole tool into the wellbore, the downhole tool comprising: a conductive tool body section; an electrically decoupling insulated tool body section mechanically coupled to the conductive tool body section; a conductive current return (CR) tool body section mechanically coupled to the electrically decoupling insulated tool body section, the conductive CR tool body section configured for direct contact with the formation; a pad mounted on the conductive tool body section, wherein the pad comprises: a conductive plate that injects current into the formation at a frequency in a range above 100 kHz and below 10 MHz; at least one button electrode that measures current injected into the formation; and a standoff spacer affixed to the conductive plate, the standoff spacer configured for direct contact with the formation; and extendable suspension means affixed to the conductive plate, that, when extended, cause direct contact between the standoff spacer and the formation; positioning the pad adjacent to the subterranean formation for electrically coupling thereto without direct contact therewith; passing an electrical signal I having a frequency in a range above 100 kHz and below 10 MHz into the subterranean formation; and measuring at least one downhole parameter of the formation from the electrical signal I at a location along the conductive CR tool body section electrically decoupled from the pad. ### Claim 15 (depends on 14) The method of claim 14, further comprising deriving an image of the formation surrounding the borehole. ### Claim 16 (depends on 14) The method of claim 14, further comprising applying a phase correction based on a spacing between the current injector electrode and a location of measurement on the conductive current return (CR) tool body section. ### Claim 17 (depends on 14) The method of claim 14, wherein positioning the pad adjacent to the subterranean formation comprises separating the pad by a standoff amount S based on the thickness of the standoff spacer. ### Claim 18 (depends on 14) The method of claim 14, further comprising injecting current into the formation at a frequency above 1 MHz.