# US 10,502,602 B2 · Apparatus and method for measuring velocity and composition of material in and adjacent to a borehole > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,502,602 B2 - Document ID: US10502602B2 - Status: Granted - Kind: B2 - Application number: 14/874,835 - Filed: 2015-10-05 - Published: 2016-04-07 - Granted: 2019-12-10 - Earliest claimed: 2014-10-06 - Assignees: Wollin Ventures, Inc. - Applicants: Wollin Ventures, Inc. - Inventors: Ernest Wollin - Web page: https://patentgrep.com/patent/US10502602B2 ## CPC - G01F 1/716: using electron paramagnetic resonance [EPR] or nuclear magnetic resonance [NMR] - E21B 47/10: Locating fluid leaks, intrusions or movements - G01N 24/081: {Making measurements of geologic samples, e.g. measurements of moisture, pH, porosity, permeability, tortuosity or viscosity} - 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} - G01R 33/4835: {of multiple slices} - G01R 33/34076: {Birdcage coils} - G01R 33/381: using electromagnets - G01R 33/383: using permanent magnets - G01F: MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME - E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS - 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) - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) ## Abstract This disclosure provides systems, methods, and apparatus for measuring flow in and around a borehole of an earth formation. A flow measurement device can include a magnet configured to generate a static solenoidal magnetic field with a field intensity that decreases in strength peripherally from the magnet, an electromagnet disposed around the magnet and configured to generate a time varying solenoidal magnetic field, and a radio frequency (RF) coil disposed around the magnet and configured to generate an RF magnetic field transverse to the static solenoidal magnetic field. The flow measurement device can calculate a flow velocity in and around the flow measurement device based upon a signal received by the RF coil. ## Claims ### Claim 1 A flow measurement device for measuring flow in a region of interest in or around a borehole of an earth formation, comprising: a magnet configured to generate a static solenoidal magnetic field with a field intensity that decreases in strength peripherally from the magnet; an electromagnet disposed around the magnet and configured to generate a time varying solenoidal magnetic field; and a radio frequency (RF) coil disposed around the magnet and configured to: generate an RF magnetic field transverse to the static solenoidal magnetic field and rotating at the Larmor radio frequency corresponding to the field intensity in the region of interest around the flow measurement device; and output a received signal, the received signal induced by a magnetic field around the RF coil. ### Claim 2 (depends on 1) The flow measurement device of claim 1, wherein the electromagnet is a helical coil disposed around the magnet. ### Claim 3 (depends on 1) The flow measurement device of claim 1, wherein the RF coil comprises a birdcage coil disposed around the magnet. ### Claim 4 (depends on 1) The flow measurement device of claim 1, wherein the RF coil comprises a first birdcage coil disposed around the magnet and configured to operate at a first frequency, and a second birdcage coil disposed around the magnet and configured to operate at a second frequency. ### Claim 5 (depends on 1) The flow measurement device of claim 1, wherein the RF coil comprises a transmitting birdcage coil disposed around the magnet and configured to generate the RF magnetic field, and a receiving birdcage coil disposed around the magnet and configured to output the received signal. ### Claim 6 (depends on 1) The flow measurement device of claim 1, wherein the RF coil comprises a quadrature coil. ### Claim 7 (depends on 1) The flow measurement device of claim 1, wherein the region of interest around the flow measurement device is a surface of a prolate or oblate spheroid having a finite thickness. ### Claim 8 (depends on 1) The flow measurement device of claim 1, further comprising a controller configured to calculate a flow velocity through the region of interest around the flow measurement device based on the received signal. ### Claim 9 (depends on 8) The flow measurement device of claim 8, wherein the controller is further configured to: select the Larmor frequency to correspond to the region of interest around the flow measurement device; adjust a magnitude of a time varying current applied to the electromagnet to maximize a magnitude of a first side band of the received signal; and adjust a magnitude of an RF current applied to the RF coil to maximize the received signal. ### Claim 10 (depends on 9) The flow measurement device of claim 9, wherein the controller is further configured to: calculate a mean dwell time of spins in the region of interest around the flow measurement device based on the magnitude of the RF current applied to the RF coil; and calculate the flow velocity through the region of interest around the flow measurement device based on the received signal. ### Claim 11 A method of measuring flow in or around a region of interest in a borehole in an earth formation, comprising: inserting a flow measurement device into the borehole in the earth formation, the flow measurement device comprising a magnet, an electromagnet disposed around the magnet, and a radio frequency (RF) coil disposed around the magnet; generating, using the magnet, a static solenoidal magnetic field, wherein the static solenoidal magnetic field has a field intensity that decreases in strength peripherally from the magnet; generating, using the electromagnet, a time varying solenoidal magnetic field; generating, using the RF coil, an RF magnetic field transverse to the static solenoidal magnetic field and rotating at a Larmor radio frequency corresponding to the field intensity in the region of interest around the flow measurement device; and receiving a received signal induced in the RF coil by a magnetic field around the RF coil. ### Claim 12 (depends on 11) The method of claim 11, wherein the electromagnet is a helical coil disposed around the magnet. ### Claim 13 (depends on 11) The method of claim 11, wherein the RF coil comprises a birdcage coil disposed around the magnet. ### Claim 14 (depends on 11) The method of claim 11, wherein the RF coil comprises a first birdcage coil disposed around the magnet and configured to operate at a first frequency, and a second birdcage coil disposed around the magnet and configured to operate at a second frequency. ### Claim 15 (depends on 11) The method of claim 11, wherein the RF coil comprises a transmitting birdcage coil disposed around the magnet and configured to generate the RF magnetic field, and a receiving birdcage coil disposed around the magnet and configured to output the received signal. ### Claim 16 (depends on 11) The method of claim 11, wherein the RF coil comprises a quadrature coil. ### Claim 17 (depends on 11) The method of claim 11, wherein the region of interest around the flow measurement device is a surface of a prolate or oblate spheroid having a finite thickness. ### Claim 18 (depends on 11) The method of claim 11, further comprising calculating a flow velocity through the region of interest around the flow measurement device based on the received signal. ### Claim 19 (depends on 18) The method of claim 18, further comprising: selecting the Larmor frequency to correspond to the region of interest around the flow measurement device; adjusting a magnitude of a time varying current applied to the electromagnet to maximize a magnitude of a first side band of the received signal; and adjusting a magnitude of an RF current applied to the RF coil to maximize the received signal. ### Claim 20 (depends on 19) The method of claim 19, further comprising: calculating a mean dwell time of spins in the region of interest around the flow measurement device based on the magnitude of the RF current applied to the RF coil; and calculating the flow velocity through the region of interest around the flow measurement device based on the received signal.