# US 10,502,799 B2 · Fiber optic nuclear magnetic resonance sensor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,502,799 B2 - Document ID: US10502799B2 - Status: Granted - Kind: B2 - Application number: 15/549,052 - Filed: 2015-03-31 - Published: 2018-02-08 - Granted: 2019-12-10 - Earliest claimed: 2015-03-31 - Assignees: Halliburton Energy Services, Inc. - Applicants: Halliburton Energy Services, Inc. - Inventors: George David Goodman; Burkay Donderici - Web page: https://patentgrep.com/patent/US10502799B2 ## CPC - G01R 33/3692: {involving signal transmission without using electrically conductive connections, e.g. wireless communication or optical communication of the MR signal or an auxiliary signal other than the MR signal} - G01R 33/323: {Detection of MR without the use of RF or microwaves, e.g. force-detected MR, thermally detected MR, MR detection via electrical conductivity, optically detected MR} - G01V 3/32: operating with electron or nuclear magnetic resonance - G01N 24/081: {Making measurements of geologic samples, e.g. measurements of moisture, pH, porosity, permeability, tortuosity or viscosity} - G01R 33/383: using permanent magnets - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) - G01V: GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS (means for indicating the location of accidentally buried, e.g. snow-buried, persons A63B29/02) - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) ## Abstract Various embodiments include a fiber optic nuclear magnetic resonance (NMR) sensor tool device and systems. One such tool includes a permanent magnet that generates a static magnetic field. A transmit antenna in the tool can operate to transmit a time-varying signal that is orthogonal to the static magnetic field. A fiber optic sensor element includes a coating that phase modulates a light signal traveling in the fiber when the coating is exposed to a varying field (e.g., a received, reflected magnetic field corresponding to the transmitted time-varying signal). The coating may be one of a magnetostrictive coating or a piezoelectric coating. Additional apparatus, systems, and methods are disclosed. ## Claims ### Claim 1 A nuclear magnetic resonance (NMR) sensor device, comprising: a magnet that generates a static magnetic field, the magnet having a north pole and opposing south pole; a transmit antenna to transmit a time-varying magnetic field at selected locations within a formation; and a sensitive fiber optic sensor element having a coating to modulate a light signal in the sensor element in response to being exposed to a received time-varying magnetic field resulting from the transmitted time-varying magnetic field, the sensitive fiber optic sensor element comprising a first and second sensor element, wherein the first sensor element is located adjacent the north pole of the magnet and the second sensor element is located adjacent the south pole of the magnet. ### Claim 2 (depends on 1) The sensor device of claim 1, wherein the time-varying magnetic field is orthogonal to the static magnetic field. ### Claim 3 (depends on 1) The sensor device of claim 1, further comprising an interferometric receiver coupled to the sensitive fiber optic sensor element. ### Claim 4 (depends on 3) The sensor device of claim 3, wherein the interferometric receiver is coupled to the sensitive fiber optic sensor element through insensitive optical fiber. ### Claim 5 (depends on 1) The sensor device of claim 1, wherein the sensitive fiber optic sensor element is located in the device and disposed parallel to the time-varying magnetic field. ### Claim 6 (depends on 1) The sensor device of claim 1, wherein the coating comprises one of a magnetostrictive material or a piezoelectric material to phase modulate the light signal in the sensitive fiber optic sensor element. ### Claim 7 (depends on 1) The sensor device of claim 1, wherein the sensitive fiber optic sensor element comprises a plurality of sections of coated optical fiber coupled together by sections of uncoated optical fiber. ### Claim 8 (depends on 1) The sensor device of claim 1, wherein the coating is divided into sections, and wherein some of the sections are located at different poles of the magnet. ### Claim 9 A nuclear magnetic resonance (NMR) sensor device, comprising: a permanent magnet that generates a static magnetic field, the magnet having a north pole and opposing south pole; a transmit antenna structure to transmit a time-varying magnetic field in a sensitive volume, the transmit antenna structure comprising an RF magnetic field radiation apparatus; a receive sensor comprising a sensitive fiber optic sensor element having a coating to phase modulate or amplitude modulate a light signal in the element in response to amplitude or frequency variations in an echo signal resulting from the time-varying magnetic field, the sensitive fiber optic sensor element having a first sensor element and a second sensor element; wherein the first sensor element is located adjacent the north pole of the magnet and the second sensor element is located adjacent the south pole of the magnet, and an optical receiver coupled to the receive sensor, the optical receiver configured to provide a modulated electrical signal representative of the phase modulated light signal. ### Claim 10 (depends on 9) The sensor device of claim 9, further comprising an NMR acquisition device coupled to the transmit antenna structure through a radio frequency transmitter. ### Claim 11 (depends on 10) The sensor device of claim 10, wherein the NMR acquisition device is coupled to the optical receiver and configured to demodulate the electrical signal. ### Claim 12 (depends on 9) The sensor device of claim 9, wherein the sensitive fiber optic sensor element comprises a magnetically or electrically field sensitive coating. ### Claim 13 A borehole inspection system, comprising: a downhole tool housing including a fiber optic nuclear magnetic resonance (NMR) sensor tool, the sensor tool comprising: a magnet that generates a static magnetic field, the magnet having a north pole and opposing south pole; a transmit antenna configured to transmit a time-varying magnetic field that is orthogonal to the static magnetic field; and a sensitive fiber optic sensor element having a coating configured to phase or amplitude modulate a light signal in the element in response to amplitude and/or frequency variations in a reflected signal resulting from the time-varying magnetic field, the sensitive fiber optic sensor element having a first sensor element and a second sensor element, wherein the first sensor element is located adjacent the north pole of the magnet and the second sensor element is located adjacent the south pole of the magnet. ### Claim 14 (depends on 13) The borehole system of claim 13, wherein the system comprises a wireline tool and the downhole tool is disposed in the wireline tool. ### Claim 15 (depends on 14) The borehole system of claim 14, wherein the fiber optic NMR sensor is coupled to a logging system for logging geological formation characteristics. ### Claim 16 (depends on 13) The borehole system of claim 13, wherein the system comprises a drill string tool and the downhole tool is disposed in the drill string tool. ### Claim 17 (depends on 16) The borehole system of claim 16, wherein the downhole tool is configured to geosteer the drill string in response to signals from the fiber optic NMR sensor. ### Claim 18 A method for making nuclear magnetic resonance (NMR) measurements, the method comprising: generating a static magnetic field using a magnet having a north pole and opposing south pole; transmitting a time-variant radio-frequency signal into a geological formation; receiving a reflected time-variant signal from the geological formation; and modulating light in a fiber optic sensor element exposed to the reflected time-variant signal, in response to the reflected time-variant signal, the modulated light signal indicative of characteristics of the geological formation, wherein the fiber optic sensor element has a first sensor element and a second sensor element, the first sensor element is located adjacent the north pole of the magnet and the second sensor element is located adjacent the south pole of the magnet. ### Claim 19 (depends on 18) The method of claim 18, wherein the time-variant RF signal varies over time in amplitude or frequency. ### Claim 20 (depends on 18) The method of claim 18, further comprising: converting the modulated light signal to a modulated electrical signal; and demodulating the electrical signal to determine the characteristics of the geological formation. ### Claim 21 (depends on 20) The method of claim 20, further comprising logging the characteristics of the geological formation. ### Claim 22 (depends on 20) The method of claim 20, further comprising geosteering a drill string in response to the characteristics of the geological formation.