ESTIMATING T2-DIFFUSION PROBABILITY DENSITY FUNCTIONS FROM NUCLEAR MAGNETIC RESONANCE DIFFUSION MODULATED AMPLITUDE MEASUREMENTS

• US 20100259258A1
• Filed: 08/14/2009
• Published: 10/14/2010
• Est. Priority Date: 06/06/2006
• Status: Active Grant

• Current Assignee: Halliburton Energy Services Incorporated (Halliburton Company)
• Original Assignee: Halliburton Energy Services Incorporated (Halliburton Company)
• Inventors: Fransson, Carl-Magnus, Fransson, Kaarina T., Cherry, Ronald E.
• Granted Patent: US 8,044,662 B2
• Time in Patent Office: Days
• US Class Current: 324/303
• CPC Class Codes: G01N 24/08 by using nuclear magnetic resonance G01N24/12 takes precedence
• CPC Class Codes: G01N 24/081 Making measurements of geologic samples, e.g. measurements of moisture, pH, porosity, permeability, tortuosity or viscosity
• CPC Class Codes: G01R 33/50 based on the determination of relaxation times , e.g. T1 measurement by IR sequences; T2 measurement by multiple-echo sequences
• CPC Class Codes: G01R 33/5617 using RF refocusing, e.g. RARE
• CPC Class Codes: G01R 33/563 of moving material, e.g. flow contrast angiography
• CPC Class Codes: G01R 33/56341 Diffusion imaging
• CPC Class Codes: G01V 3/32 operating with electron or nuclear magnetic resonance

Abstract

In some embodiments, apparatus and systems, as well as methods, may operate to acquire data representing a plurality of nuclear magnetic resonance (NMR) echo trains associated with a material, such as a geological formation. Additional operations may include inverting a model of at least one of the plurality of NMR echo trains to provide an estimated distribution of transverse relaxation time constants, inverting models of selected ones of the plurality of NMR echo trains using the estimated distribution of transverse relaxation time constants to provide an estimated diffusion distribution, and inverting a model of selected ones of the plurality of NMR echo trains, using the estimated distributions of transverse relaxation time constants and diffusion, to provide an apparent and an intrinsic probability density function to identify fluid types in the material.

Claims

1. An apparatus, including:

acquisition logic to acquire data representing a plurality of nuclear magnetic resonance (NMR) echo trains associated with a material; and

processing logic to invert a model of at least one of the plurality of NMR echo trains to provide an estimated distribution of transverse relaxation time constants, to invert models of selected ones of the plurality of NMR echo trains using the estimated distribution of transverse relaxation time constants to provide an estimated diffusion distribution, and to invert models of selected ones of the plurality of NMR echo trains using the estimated distributions of transverse relaxation time constants and diffusion to provide at least one of an apparent and an intrinsic probability density function to identify fluid types in the material.

2. The apparatus of claim 1, further including:

NMR sensors to receive signals associated with the data.

3. The apparatus of claim 1, further including:

a memory to store the data.

4. The apparatus of claim 1, wherein the data includes information associated with long echo spacing and short echo spacing for the plurality of NMR echo trains.

5. The apparatus of claim 1, further including:

a telemetry transmitter to transmit the data to an above-ground computer.

6. The apparatus of claim 1, further including:

a display to display visual representations of the probability density function, the distribution of transverse relaxation time constants, and the diffusion distribution.

7. A system, including:

a downhole tool;

acquisition logic included in the downhole tool to acquire data representing a plurality of nuclear magnetic resonance (NMR) echo trains associated with a material; and

processing logic to invert a model of at least one of the plurality of NMR echo trains to provide an estimated distribution of transverse relaxation time constants, to invert models of selected ones of the plurality of NMR echo trains using the estimated distribution of transverse relaxation time constants to provide an estimated diffusion distribution, and to invert a model of selected ones of the plurality of NMR echo trains, using the estimated distributions of transverse relaxation time constants and diffusion, to provide at least one of an apparent and an intrinsic probability density function to identify fluid types in the material.

8. The system of claim 7, wherein the processing logic is included in the downhole tool.

9. The system of claim 7, further including:

a wireline coupled to the downhole tool.

10. The system of claim 7, further including:

a drill bit mechanically coupled to a drill string and the downhole tool; and

a steering mechanism to steer the drill bit responsive to the probability density function.

11. The system of claim 10, wherein the drill string includes at least one of segmented drilling pipe, casing, and coiled tubing.

12. A method, including:

acquiring data representing a plurality of nuclear magnetic resonance (NMR) echo trains associated with a material;

inverting a model of at least one of the plurality of NMR echo trains to provide an estimated distribution of transverse relaxation time constants;

inverting models of selected ones of the plurality of NMR echo trains using the estimated distribution of transverse relaxation time constants to provide an estimated diffusion distribution; and

inverting a model of selected ones of the plurality of NMR echo trains, using the estimated distributions of transverse relaxation time constants and diffusion, to provide at least one of an apparent and an intrinsic probability density function to identify fluid types in the material.

13. The method of claim 12, further including:

selecting, independently, at least two of a distribution of transverse relaxation time constants smoothness, a diffusion distribution smoothness, and a probability density function smoothness.

14. The method of claim 13, further including:

adjusting the distribution of transverse relaxation time constants smoothness, the diffusion distribution smoothness, and the probability density function smoothness to resolve the fluid types.

15. The method of claim 12, further including:

selecting a number of discrete values associated with the distribution of transverse relaxation time constants and the diffusion distribution to construct the probability density function.

16. The method of claim 12, wherein the at least one of the plurality of NMR echo trains is characterized by a long echo spacing time that is approximately equal to a short echo spacing time.

17. The method of claim 12, wherein the material comprises at least one fluid.

18. The method of claim 12, wherein the material comprises fluids within a geological formation.

19. The method of claim 12, wherein the material comprises fluids that have been withdrawn from a geological formation.

20. The method of claim 12, further including:

identifying the fluid types using the at least one apparent and intrinsic probability density function.

21. The method of claim 12, further including:

quantifying relative volumes associated with the fluid types using the at least one apparent and intrinsic probability density function.

22. A computer-readable medium having instructions stored thereon which, when executed by a computer, cause the computer to perform a method comprising:

acquiring data for a plurality of nuclear magnetic resonance (NMR) echo trains associated with a material;

inverting a model of at least one of the plurality of NMR echo trains to provide an estimated distribution of transverse relaxation time constants;

inverting models of selected ones of the plurality of NMR echo trains using the estimated distribution of transverse relaxation time constants to provide an estimated diffusion distribution; and

inverting a model of selected ones of the plurality of NMR echo trains, using the estimated distributions of transverse relaxation time constants and diffusion, to provide at least one of an apparent and intrinsic probability density function to identify fluid types in the material.

23. The computer-readable medium of claim 22, wherein the instructions, when executed by the computer, cause the computer to perform a method comprising:

acquiring the data; and

adjusting conduct of a drilling operation activity based on the probability density function in substantially real time.

24. The computer-readable medium of claim 22, wherein the instructions, when executed by the computer, cause the computer to perform a method comprising:

determining mud filtrate contamination of fluids being withdrawn from a formation based on the at least one apparent and intrinsic probability density function.

25. The computer-readable medium of claim 22, wherein the instructions, when executed by the computer, cause the computer to perform a method comprising:

acquiring the data as a portion of a diffusion modulated amplitude measurement process.