# US 9,519,075 B2 · Front tangential antenna for nuclear magnetic resonance (NMR) well logging > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,519,075 B2 - Document ID: US9519075B2 - Status: Granted - Kind: B2 - Application number: 14/436,857 - Filed: 2014-05-06 - Published: 2016-06-16 - Granted: 2016-12-13 - Earliest claimed: 2014-05-06 - Assignees: Halliburton Energy Services, Inc. - Applicants: Halliburton Energy Services, Inc. - Inventors: Rebecca Jachmann; George David Goodman - Web page: https://patentgrep.com/patent/US9519075B2 ## CPC - G01V 3/32: operating with electron or nuclear magnetic resonance - E21B 47/00: Survey of boreholes or wells (monitoring pressure or flow of drilling fluid E21B21/08) - E21B 47/13: by electromagnetic energy, e.g. radio frequency - G01R 33/341: comprising surface coils - G01R 33/3808: {Magnet assemblies for single-sided MR wherein the magnet assembly is located on one side of a subject only; Magnet assemblies for inside-out MR, e.g. for MR in a borehole or in a blood vessel, or magnet assemblies for fringe-field MR} - G01V: GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS (means for indicating the location of accidentally buried, e.g. snow-buried, persons A63B29/02) - E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) ## Abstract The magnet and antenna assemblies of a logging tool can be arranged according to geometries optimal for concentric or eccentric well logging operations. In an example configuration, a logging tool can include a magnet, a magnetic core made of a magnetically permeable material, and an antenna. The outward path of the antenna can be positioned along a surface of the magnetically permeable magnetic core that faces away from the magnet, and the return path of the antenna can also be positioned along a surface that faces away from the magnet. ## Claims ### Claim 1 A nuclear magnetic resonance system for well logging using an axially-extending tool, the system comprising: a magnet; a core having a first surface facing the magnet and one or more other surfaces facing away from the magnet; and an antenna positioned along at least one of the one or more other surfaces, the antenna comprising a first loop of electrically conductive material and a second loop of electrically conductive material, the first and second loops comprising a common segment extending along an axis of the axially-extending tool. ### Claim 2 (depends on 1) The system of claim 1, wherein the common segment is positioned along a surface of the core opposite the magnet. ### Claim 3 (depends on 2) The system of claim 2, wherein the core is between the magnet and the antenna. ### Claim 4 (depends on 1) The system of claim 1, wherein the common segment is positioned along a surface of the core that extends along the axis of the axially-extending tool. ### Claim 5 (depends on 4) The system of claim 4, wherein tool further comprises an additional magnet; wherein the core is between the magnet and the additional magnet. ### Claim 6 (depends on 1) The system of claim 1, wherein the first loop and the second loop are between the core and a point beyond the radial periphery of the tool. ### Claim 7 (depends on 6) The system of claim 6, comprising an electronic controller in communication with the magnet and the antenna assembly, the electronic controller being programmed to cause the magnet to induce a first magnetic field at the point and to cause the antenna assembly to induce a radio frequency magnetic field at the point, wherein the radio frequency magnetic field is orthogonal to the first magnetic field at the point. ### Claim 8 (depends on 1) The system of claim 1, wherein the first loop is symmetric to the second loop. ### Claim 9 (depends on 1) The system of claim 1, wherein the first loop further comprises a first segment; the second loop further comprises a second segment; the common segment extends from a first trace; and the first segment and the second segment converge into a second trace. ### Claim 10 (depends on 9) The system of claim 9, wherein the common segment diverges to form the first segment and the second segment. ### Claim 11 (depends on 9) The system of claim 9, wherein the common segment, the first segment, and the second segment extend axially from a notional arc, and the common segment extends axially from a center of the arc. ### Claim 12 (depends on 11) The system of claim 11, wherein the first segment and the second segment extend axially from positions on the arc a distance from the center of the arc. ### Claim 13 (depends on 12) The system of claim 12, wherein an angular distance between the common segment and the first segment is in a range from about 80 degrees to about 85 degrees relative to a focus of the arc. ### Claim 14 (depends on 1) The system of claim 1, wherein the one or more other surfaces comprise a planar surface. ### Claim 15 (depends on 1) The system of claim 1, wherein the one or more other surfaces comprise a curved surface. ### Claim 16 (depends on 1) The system of claim 1, wherein the core is composed of a material having a relative magnetic permeability in a range from about 9 to 20. ### Claim 17 (depends on 1) The system of claim 1, wherein the common segment comprises a plurality of conductors that extend in a common direction. ### Claim 18 (depends on 7) The system of claim 7, wherein the first magnetic field is a static magnetic field. ### Claim 19 (depends on 1) The system of claim 1, wherein the common segment is disposed near a surface of the core opposite the magnet. ### Claim 20 (depends on 1) The system of claim 1, wherein the first loop and the second loop are disposed between the core and a volume beyond the radial periphery of the tool. ### Claim 21 (depends on 20) The system of claim 20, comprising an electronic controller in communication with the magnet and the antenna assembly, the electronic controller being programmed to cause the magnet to induce a first magnetic field at the volume and to cause the antenna assembly to induce a radio frequency magnetic field at the volume, wherein the radio frequency magnetic field is orthogonal to the first magnetic field at the volume. ### Claim 22 A method comprising: obtaining an axially extending magnetic resonance well logging tool comprising: a magnet; and a core having a first surface facing the magnet and one or more other surfaces facing away from the magnet; positioning an antenna along at least one of the one or more other surfaces, wherein the antenna comprises a first loop of electrically conductive material and a second loop of electrically conductive material, and the first and second loops comprise a common segment extending along an axis of the axially-extending tool. ### Claim 23 (depends on 22) The method of claim 22, wherein positioning the antenna comprises positioning the common segment along a surface of the core opposite the magnet. ### Claim 24 (depends on 23) The method of claim 23, wherein positioning the antenna comprises positioning the antenna such that the core is between the magnet and the antenna. ### Claim 25 (depends on 22) The method of claim 22, wherein positioning the antenna comprises positioning the common segment along a surface of the core that extends along the axis of the axially-extending tool. ### Claim 26 (depends on 22) The method of claim 22, wherein positioning the antenna comprises positioning the first loop and the second loop between the core and a point beyond the radial periphery of the tool. ### Claim 27 (depends on 26) The method of claim 26, further comprising: using the magnet to induce a first magnetic field at the point; and using the antenna assembly to induce a radio frequency magnetic field at the point; wherein the radio frequency magnetic field is orthogonal to the first magnetic field at the point. ### Claim 28 (depends on 22) The method of claim 22, wherein the first loop is symmetric to the second loop. ### Claim 29 (depends on 22) The method of claim 22, wherein the first loop further comprises a first segment; the second loop further comprises a second segment; the common segment extends from a first trace; and the first segment and the second segment converge into a second trace. ### Claim 30 (depends on 29) The method of claim 29, wherein the common segment diverges to form the first segment and the second segment. ### Claim 31 (depends on 29) The method of claim 29, wherein positioning the antenna comprises positioning the antenna such that the common segment, the first segment, and the second segment extend axially from a notional arc, and the common segment extends axially from a center of the arc. ### Claim 32 (depends on 31) The method of claim 31, wherein positioning the antenna comprises positioning the antenna such that the first segment and the second segment extend axially from positions on the arc a distance from the center of the arc. ### Claim 33 (depends on 32) The method of claim 32, wherein positioning the antenna comprises positioning the antenna such that an angular distance between the common segment and the first segment is in a range from about 80 degrees to about 85 degrees relative to a focus of the arc. ### Claim 34 (depends on 22) The method of claim 22, wherein positioning the antenna comprises positioning the common segment near a surface of the core opposite the magnet. ### Claim 35 (depends on 22) The method of claim 22, wherein positioning the antenna comprises positioning the first loop and the second loop between the core and a volume beyond the radial periphery of the tool. ### Claim 36 (depends on 35) The method of claim 35, further comprising: using the magnet to induce a first magnetic field at the volume; and using the antenna assembly to induce a radio frequency magnetic field at the volume; wherein the radio frequency magnetic field is orthogonal to the first magnetic field at the volume.