Nucleur magnetic resonance system with feedback induction coils

Patent metadata

Field	Value
Publication number	US-9715032-B2
Application number	US-201313952999-A
Country	US
Kind code	B2
Filing date	Jul 29, 2013
Priority date	Jul 31, 2012
Publication date	Jul 25, 2017
Grant date	Jul 25, 2017

Abstract

A nuclear magnetic resonance (NMR) system that uses a feedback induction coil to detect NMR signals generated within a substance is described herein. In one embodiment, the NMR system uses the Earth's magnetic field in conjunction with a transmitter coil that applies NMR sequences to a formation. The NMR sequences generate a weak NMR signal within the formation due to the weakness of the Earth's magnetic field. This weak NMR signal is detected using the feedback induction coil.

First claim

What is claimed is:

1. A nuclear magnetic resonance (NMR) system, the system comprising:
a transmitter coil;
an NMR transmitter configured to drive the transmitter coil to apply an NMR pulse sequence to a substance, wherein the NMR pulse sequence is comprised of a series of radio-frequency pulses;
a feedback induction coil configured to detect NMR signals generated within the substance in response to the NMR pulse sequence, wherein the feedback induction coil comprises:
a primary coil;
a feedback coil; and
feedback electronics (i) coupled to the primary coil and the feedback coil and (ii)

configured to detect the NMR signals generated within the substance by applying a current to the feedback coil such that the current cancels a magnetic field through the primary coil produced by the NMR signals.

2. The system of claim 1 , further comprising:
a wellbore tool comprising the feedback induction coil and the transmitter coil.

3. The system of claim 2 , wherein the wellbore tool is a wireline tool.

4. The system of claim 1 , further comprising:
a wellbore tool comprising the feedback induction coil; and
a surface module comprising the transmitter coil.

5. The NMR system of claim 1 , further comprising:
a surface module comprising the feedback induction coil and the transmitter coil.

6. The system of claim 1 , wherein the primary coil has at least 1000 turns.

7. The system of claim 1 , wherein the feedback induction coil includes a core that has a permeability of at least 1000.

8. The system of claim 1 , wherein the feedback induction coil has a cross-sectional area no greater than 400 cm 2 .

9. The system of claim 1 , wherein the feedback induction coil is configured to apply an NMR sequence to the substance.

10. A method for analyzing a substance using nuclear magnetic resonance (NMR), the method comprising:
applying an NMR pulse sequence to the substance, wherein the NMR pulse sequence is comprised of a series of radio-frequency pulses; and
detecting NMR signals generated by the NMR pulse sequence using a feedback induction coil that comprises a primary coil and a feedback coil, wherein the detecting comprises applying a current to the feedback coil such that the current cancels a magnetic field through the primary coil produced by the NMR signals.

11. The method of claim 10 , wherein the NMR signals are generated using a magnetic field of the Earth.

12. The method of claim 11 , wherein the NMR pulse sequence is applied using a transmitter coil.

13. The method of claim 12 , wherein the feedback induction coil and the transmitter coil are located in a wellbore.

14. The method of claim 12 , wherein the feedback induction coil and the transmitter coil are located at a surface location.

15. The method of claim 12 , wherein the feedback induction coil is located in a wellbore and the transmitter coil is located at a surface location.

16. The method of claim 10 , wherein the primary coil has at least 1000 turns.

17. A wellbore tool comprising:
a transmitter coil;
a nuclear magnetic resonance (NMR) transmitter configured to drive the transmitter coil to apply an NMR pulse sequence to a substance, the NMR pulse sequence comprised of a series of radio-frequency pulses; and
a feedback induction coil configured to detect NMR signals generated within the substance in response to the NMR pulse sequence, wherein the feedback induction coil comprises:
a primary coil;
a feedback coil; and
feedback electronics (i) coupled to the primary coil and the feedback coil and (ii)

configured to detect the NMR signals generated within the substance by applying a current to the feedback coil such that the current cancels a magnetic field through the primary coil produced by the NMR signals.

Assignees

• Schlumberger Technology Corp

Inventors

• Song Yiqiao
• Wilt Michael
• Sen Pabitra

Classifications

• G01N24/08

  by using nuclear magnetic resonance (G01N24/12 takes precedence) · CPC title

• G01R33/445

  MR involving a non-standard magnetic field B0, e.g. of low magnitude as in the earth's magnetic field or in nanoTesla spectroscopy, comprising a polarizing magnetic field for pre-polarisation, B0 with a temporal variation of its magnitude or direction such as field cycling of B0 or rotation of the direction of B0, or spatially inhomogeneous B0 like in fringe-field MR or in stray-field imaging · CPC title

• G01R33/3621

  NMR receivers or demodulators, e.g. preamplifiers, means for frequency modulation of the MR signal using a digital down converter, means for analog to digital conversion [ADC] or for filtering or processing of the MR signal such as bandpass filtering, resampling, decimation or interpolation · CPC title

• G01N24/085

  Analysis of materials for the purpose of controlling industrial production systems · CPC title

• G01N24/081

  Making measurements of geologic samples, e.g. measurements of moisture, pH, porosity, permeability, tortuosity or viscosity · CPC title