# US 8,464,796 B2 · Fluid resistivity measurement tool > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,464,796 B2 - Document ID: US8464796B2 - Status: Granted - Kind: B2 - Application number: 12/849,327 - Filed: 2010-08-03 - Published: 2012-02-09 - Granted: 2013-06-18 - Earliest claimed: 2010-08-03 - Assignees: Schlumberger Technology Corporation - Applicants: Albert Hoefel; Kent D. Harms; Michael J. Stucker - Inventors: Albert Hoefel; Kent D. Harms; Michael J. Stucker - Web page: https://patentgrep.com/patent/US8464796B2 ## CPC - E21B 49/08: Obtaining fluid samples or testing fluids, in boreholes or wells - E21B 49/0875: {determining specific fluid parameters} - E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS ## Abstract A downhole tool configured for conveyance within a borehole extending into a subterranean formation, wherein the downhole tool comprises a sensor assembly comprising a housing, a cap coupled to an end of the housing, a flow-line tube disposed within the housing and configured to receive fluid from the formation, a first winding disposed within the housing and configured to induce an electrical current in the fluid, and a second winding disposed within the housing and configured to detect the electrical current induced in the fluid by the first winding. ## Claims ### Claim 1 An apparatus, comprising: a downhole tool configured for conveyance within a borehole extending into a subterranean formation, wherein the downhole tool comprises a sensor assembly comprising: a housing; a cap removably coupled to an end of the housing; a flow-line tube disposed within the housing and configured to receive fluid from the formation or borehole; a first winding disposed within the housing and configured to induce an electrical current in the fluid; and a second winding disposed within the housing and configured to detect the electrical current induced in the fluid by the first winding; a first chassis comprising a first flow-line extending therethrough; and a second chassis coupled to the first chassis and comprising a second flow-line extending therethrough, wherein the housing is disposed between the first and second chassis, and wherein the flow-line tube fluidly couples the first and second flow-lines. ### Claim 2 (depends on 1) The apparatus of claim 1 wherein the flow-line tube extends externally from the housing and the cap. ### Claim 3 (depends on 1) The apparatus of claim 1 wherein the sensor assembly further comprises a biasing member disposed between the housing and the first chassis. ### Claim 4 (depends on 1) The apparatus of claim 1 wherein the flow-line tube is electrically insulated. ### Claim 5 (depends on 1) The apparatus of claim 1 wherein the flow-line tube comprises a first portion having a first diameter and a second portion having a second diameter, wherein the second diameter is larger than the first diameter, and wherein the second portion is disposed between the first and second windings. ### Claim 6 (depends on 5) The apparatus of claim 5 wherein the second portion is removably coupled to the first portion. ### Claim 7 (depends on 1) The apparatus of claim 1 wherein the housing comprises a non-magnetic material. ### Claim 8 (depends on 1) The apparatus of claim 1 wherein the sensor assembly further comprises a detector thermally coupled to the flow-line tube and configured to detect a temperature of the flow-line tube. ### Claim 9 (depends on 1) The apparatus of claim 1 wherein the sensor assembly further comprises a detector electrically coupled to the flow-line tube and configured to detect an electrical leakage from the flow-line tube. ### Claim 10 (depends on 1) The apparatus of claim 1 wherein the sensor assembly further comprises a detector electrically coupled to the second winding and configured to detect a current of the second winding. ### Claim 11 (depends on 1) The apparatus of claim 1 wherein the sensor assembly further comprises a detector electrically coupled to the second winding and configured to detect a voltage of the second winding. ### Claim 12 (depends on 1) The apparatus of claim 1 wherein the downhole tool is configured for conveyance within the borehole via drill string. ### Claim 13 (depends on 1) The apparatus of claim 1 wherein the downhole tool is configured for conveyance within the borehole via wireline. ### Claim 14 A method, comprising: conveying a downhole tool within a borehole extending into a subterranean formation, wherein the downhole tool comprises a sensor assembly comprising: a housing; a cap removably coupled to an end of the housing; a flow-line tube disposed within the housing; a first winding disposed within the housing adjacent the flow-line tube; and a second winding disposed within the housing adjacent the flow-line tube; drawing fluid from the formation or borehole into the downhole tool and through the flow-line tube; inducing an electrical current in the fluid within the flow-line tube; detecting the electrical current induced in the fluid by the first winding; and detecting an electrical leakage from the flow-line tube with a detector electrically coupled to the flow-line tube. ### Claim 15 (depends on 14) The method of claim 14 further comprising detecting a temperature of the flow-line tube with a detector thermally coupled to the flow-line tube. ### Claim 16 (depends on 14) The method of claim 14 further comprising detecting a current of the second winding with a detector electrically coupled to the second winding. ### Claim 17 (depends on 14) The method of claim 14 further comprising detecting a voltage of the second winding with a detector electrically coupled to the second winding. ### Claim 18 (depends on 14) The method of claim 14 wherein conveying the downhole tool within the borehole comprises conveyance via one of wireline and drill string.