# US 10,502,045 B2 · Monitoring substances in a well annulus > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,502,045 B2 - Document ID: US10502045B2 - Status: Granted - Kind: B2 - Application number: 15/576,189 - Filed: 2015-06-24 - Published: 2018-05-17 - Granted: 2019-12-10 - Earliest claimed: 2015-06-24 - Assignees: Halliburton Energy Services, Inc. - Applicants: Halliburton Energy Services, Inc. - Inventors: Ahmed E. Fouda; Glenn A. Wilson; Burkay Donderici - Web page: https://patentgrep.com/patent/US10502045B2 ## CPC - E21B 47/005: Monitoring or checking of cementation quality or level - E21B 47/047: Liquid level (measuring depth or liquid level using radioactive markers E21B47/053) - G01V 3/20: operating with propagation of electric current - G01V 3/26: operating with magnetic or electric fields produced or modified either by the surrounding earth formation or by the detecting device (with electromagnetic waves G01V3/30) - G01V 3/34: Transmitting data to recording or processing apparatus; Recording data - E21B 33/14: for cementing casings into boreholes - E21B 47/06: Measuring temperature or pressure - 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 A system can include a current source electrically connected to casing in a wellbore, and a sensor including a monitoring electrode, a potential difference between the casing and the electrode resulting from current applied by the current source, and the potential difference indicating an impedance of a substance in an annulus external to the casing. A method can include positioning sensors spaced apart along a casing in a wellbore, each of the sensors including an electrode in electrical contact with a substance in an annulus, inducing current in the casing, and measuring a potential difference between the casing and the electrode at each sensor. Another system can include a current source, the current source being electrically connected to casing in a wellbore, and a sensor including a monitoring electrode and an electro-optical transducer that converts a potential difference between the casing and the electrode into strain in an optical waveguide. ## Claims ### Claim 1 A well monitoring system, comprising: a current source electrically connected to casing in a wellbore to induce a current in the casing; at least one sensor including at least one monitoring electrode; an insulator positioned between the casing and the at least one monitoring electrode to partially electrically insulate the at least one monitoring electrode from the current in the casing; and wherein an electrical potential difference between the casing and the monitoring electrode results from current applied by the current source, and wherein the potential difference indicates an impedance due in part to at least one substance in an annulus formed between the casing and an earth formation. ### Claim 2 (depends on 1) The system of claim 1, wherein the insulator is between 0.05 inches and 0.5inches thick. ### Claim 3 (depends on 1) The system of claim 1, wherein the at least one sensor comprises multiple longitudinally spaced apart sensors. ### Claim 4 (depends on 3) The system of claim 3, wherein change of physical properties of the substance through the annulus is indicated by changes in the potential difference at successive ones of the sensors along the casing, and wherein the change of physical properties is selected from the group consisting of, during a life history of the well, a) displacement, b) curing, c) fluid inflow and d) fluid outflow. ### Claim 5 (depends on 3) The system of claim 3, wherein the at least one substance comprises multiple substances, and wherein an interface between the substances is indicated by different potential differences between adjacent sensors. ### Claim 6 (depends on 1) The system of claim 1, wherein a cure state of the substance is indicated by the potential difference. ### Claim 7 (depends on 1) The system of claim 1, wherein the potential difference indicates at least one of the group consisting of a proportion of the substance in the annulus and a discrimination of different fluids in the annulus. ### Claim 8 A method of monitoring a well, the method comprising: positioning multiple sensors spaced apart along a casing in a wellbore, each of the sensors comprising at least one electrode and an insulator positioned between the at least one electrode and the casing to partially electrically insulate the at least one monitoring electrode from the current in the casing, and each of the sensors forms an electrical circuit with at least one substance in an annulus formed between the casing and the wellbore; injecting current in the casing; and measuring a potential difference between the casing and the electrode at each sensor. ### Claim 9 (depends on 8) The method of claim 8, further comprising determining a cure state of the substance at each sensor based on the potential difference. ### Claim 10 (depends on 8) The method of claim 8, further comprising monitoring a change in physical properties of the substance through the annulus, based on changes in the potential difference at each sensor, and wherein the change in physical properties is selected from the group consisting of, during a life history of the well, a) displacement, b) curing, c) fluid inflow and d) fluid outflow. ### Claim 11 (depends on 8) The method of claim 8, wherein the at least one substance comprises multiple substances, and further comprising determining a location of an interface between the substances based on different potential differences at adjacent sensors. ### Claim 12 (depends on 8) The method of claim 8, further comprising determining, based on the potential difference, at least one of the group consisting of a proportion of the substance in the annulus and a discrimination of different fluids. ### Claim 13 (depends on 8) The method of claim 8, wherein the insulator is between 0.05 inches and 0.5 inches thick. ### Claim 14 (depends on 13) The method of claim 13, further comprising detecting optical scattering in the optical waveguide as an indication of the strain. ### Claim 15 A well monitoring system, comprising: a current source, the current source being electrically connected to casing in a wellbore to induce a current in the casing; at least one sensor including at least one monitoring electrode, and a converter that converts an electrical potential difference; and an insulator positioned between the casing and the at least one monitoring electrode to partially electrically insulate the at least one monitoring electrode from the current in the casing. ### Claim 16 (depends on 15) The system of claim 15, wherein the at least one sensor comprises multiple sensors spaced apart along the casing. ### Claim 17 (depends on 16) The system of claim 16, wherein changes in the potential difference at successive ones of the sensors indicates, during a life history of the well, at least one of the group consisting of displacement, curing, fluid inflow and fluid outflow. ### Claim 18 (depends on 16) The system of claim 16, wherein an interface between substances in an annulus is indicated by different potential differences between adjacent sensors. ### Claim 19 (depends on 15) The system of claim 15, wherein a cure state of a substance is indicated by the potential difference. ### Claim 20 (depends on 15) The system of claim 15, wherein the potential difference indicates at least one of the group consisting of a proportion of a substance in an annulus and a discrimination of different fluids. ### Claim 21 (depends on 15) The system of claim 15, wherein the converter converts the electrical potential difference between the casing and the electrode into strain in an optical waveguide.