Modified pulse sequence to estimate properties

Patent metadata

Field	Value
Publication number	US-10557809-B2
Application number	US-201715590963-A
Country	US
Kind code	B2
Filing date	May 9, 2017
Priority date	Mar 4, 2010
Publication date	Feb 11, 2020
Grant date	Feb 11, 2020

Abstract

Methods and related systems are described for estimating fluid or rock properties from NMR measurements. A modified pulse sequence is provided that can directly provide moments of relaxation-time or diffusion distributions. This pulse sequence can be adapted to the desired moment of relaxation-time or diffusion coefficient. The data from this pulse sequence provides direct estimates of fluid properties such as average chain length and viscosity of a hydrocarbon. In comparison to the uniformly-spaced pulse sequence, these pulse sequences are faster and have a lower error bar in computing the fluid properties.

First claim

What is claimed is:

1. A method of estimating a property of a material using nuclear magnetic resonance (NMR), the method comprising:
inducing a measurable change in the material using an NMR pulse;
after a predetermined time interval, making a measurement of a material response to the induction using NMR, wherein the material response exponentially decays following the induction;
repeating the inducing and the measuring at non-uniform predetermined time intervals, wherein the non-uniform predetermined time intervals are determined based on the property to be estimated; and
estimating the property based at least in part on the measurements of the exponentially decaying material response.

2. A method according to claim 1 wherein the NMR pulse is a transverse magnetic pulse.

3. A method according to claim 1 wherein the predetermined time intervals are non-uniform in both linear and logarithmic scales.

4. A method according to claim 1 wherein the non-uniform predetermined time intervals follow a power law.

5. A method according to claim 1 wherein the non-uniform predetermined time intervals allow for the property to be directly computed from the measurements of the exponentially decaying material response.

6. A method according to claim 1 wherein the measurements are performed as part of one or more oilfield services.

7. A method according to claim 6 wherein the measurements are made downhole.

8. A method according to claim 1 wherein the material is a fluid.

9. A method according to claim 8 wherein the property is a fluid property.

10. A method according to claim 1 wherein the material is one or more rock solids and the property is a petrophysical property of the one or more rock solids.

11. A method according to claim 1 wherein the non-uniform predetermined time intervals are determined based on a moment of relaxation-time or diffusion distribution.

12. A method according to claim 1 wherein the material is a mixture of solid and liquid.

13. A method according to claim 12 wherein the property comprises a plurality of properties and the plurality of properties comprises a fluid property and a petrophysical property in porous solids.

14. A nuclear magnetic resonance (NMR) system for estimating a property of a material, the NMR system comprising:
a NMR tool adapted to (i) induce a measurable change in the material using an NMR pulse and (ii) measure a material response to the induction after a predetermined time interval; and
a processing system adapted to (i) repeat the induction and the measurement at non-uniform predetermined time intervals, wherein the non-uniform predetermined time intervals are determined based on the property to be estimated, and (ii) estimate the property based at least in part on the measurements.

15. A system according to claim 14 wherein the NMR tool transmits a transverse magnetic pulse using an antenna.

16. A system according to claim 14 wherein the non-uniform predetermined time intervals are non-uniform in both linear and logarithmic scales.

17. A system according to claim 14 wherein the non-uniform predetermined time intervals follow a power law.

18. A system according to claim 14 wherein the non-uniform predetermined time intervals allow for the property to be directly computed from the measurements.

19. A system according to claim 14 wherein the NMR system is part of an oilfield services tool.

20. A system according to claim 14 further comprising a downhole deployable tool body that houses the NMR tool.

21. A system according to claim 14 wherein the material is a fluid.

22. A system according to claim 21 wherein the property is a fluid property.

23. A system according to claim 14 wherein the material is one or more rock solids and the property is a petrophysical property of the one or more rock solids.

24. A system according to claim 14 wherein the non-uniform predetermined time intervals are determined based on a moment of relaxation-time or diffusion distribution.

25. A system according to claim 14 wherein the material is a mixture of solid and liquid.

26. A method according to claim 25 wherein the property is a fluid property in porous solids.

Assignees

• Schlumberger Technology Corp

Inventors

• Venkataramanan Lalitha
• Habashy Tarek M
• Freed Denise E

Classifications

• G01N11/16

  by measuring damping effect upon oscillatory body · CPC title

• G01N24/081 Primary

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

• G01V3/14

  operating with electron or nuclear magnetic resonance · CPC title

• G01V3/32 Primary

  operating with electron or nuclear magnetic resonance · CPC title

• G01R33/448 Primary

  Relaxometry, i.e. quantification of relaxation times or spin density (G01R33/50 takes precedence) · CPC title