Nuclear magnetic resonance method quantifying fractures in unconventional source rocks

1. A method for analyzing unconventional rock samples, the method comprising:

introducing fluid to a rock sample;

acquiring, by a computer processor, nuclear magnetic resonance (NMR) measurements of the rock sample to track fluid change in the rock sample;

calculating transverse relaxation time (T 2 ) based on the NMR measurements;

generating, by the computer processor and based on an NMR imaging, fluid distribution profiles, the fluid distribution profiles representing a movement of the fluid; and

obtaining, by the computer processor and based on the NMR imaging, a quantification of fracture volume, the quantification of the fracture volume representing an amount of fluid in a fracture.

2. The method of claim 1 , further comprising:

identifying a presence of fractures in the rock sample by measuring movement of the fluid through the rock sample over time;

predicting an extent of the fractures in the rock sample by determining fluid distribution profiles of the fluid; and

quantifying the fracture volume through a measurement of at least one fracture fluid peak in an NMR spectrum.

3. The method of claim 1 , wherein the rock sample is dried in vacuum before acquiring NMR measurements.

4. The method of claim 1 , wherein the fluid is introduced to the rock sample on one end, using a spontaneous imbibition.

5. The method of claim 1 , wherein the NMR imaging is obtained at time intervals to track spatial and temporal changes in the rock sample.

6. The method of claim 1 , wherein the transverse relaxation time (T 2 ) is obtained from a decay due to surface relaxation and bulk relaxation.

7. The method of claim 1 , wherein a Carr Purcell Meiboom Gill (CPMG) sequence is used to acquire NMR imaging at different imbibition time.

8. The method of claim 1 , wherein the fracture volume is obtained through a measurement of peak volumes by calculating an area under the curve in NMR T 2 spectra.

9. A computer system for analyzing unconventional rock samples, comprising:

a processor; and

a memory coupled to the processor, the memory storing instructions, when executed,

comprising functionality for:

acquiring nuclear magnetic resonance (NMR) measurements of a rock sample;

generating, based on NMR imaging, fluid distribution profiles, the fluid distribution profiles representing a movement of the fluid in the rock sample; and

obtaining, based on NMR imaging, a quantification of fracture volume, the quantification of the fracture volume representing the amount of the fluid in a fracture of the rock sample.

10. The computer system of claim 9 , further comprising:

identifying a presence of fractures in a rock sample by measuring movement of fluid through the rock sample over time;

predicting an extent of the fractures in the rock sample by determining fluid distribution profiles of the fluid; and

quantifying the fracture volume through a measurement of peak volumes in NMR spectra.

11. The computer system according to claim 9 , further comprising:

generating, by inversion of the NMR measurements, a spatial transverse relaxation time (T 2 ) distribution; and

generating, based on the spatial T 2 distribution, a saturation profile representing distribution of the fluid stored in the rock sample.

12. The computer system of claim 11 , wherein a NMR saturation profile may be obtained, by a computer processor and based on NMR imaging, using SPRITE DHK sequence.

13. The computer system of claim 11 , wherein the location of the fluid is determined by examining the y-axis of the saturation profile plot.

14. The computer system of claim 9 , wherein NMR imaging is obtained at time intervals to track spatial and temporal changes in the rock sample.

15. The method of claim 9 , wherein the T 2 is obtained from a decay due to surface relaxation and a bulk relaxation.

16. The computer system of claim 9 , wherein Carr Purcell Meiboom Gill (CPMG) sequence may be used to acquire NMR imaging at different imbibition time.

17. The computer system of claim 9 , wherein the fracture volume is obtained through a measurement of peak volumes by calculating area under the curve in NMR T 2 spectra.

18. A non-transitory computer readable medium storing instructions executable by a computer processor for analyzing unconventional rock samples, the instructions, when executed by the computer processor, comprising functionality for:

acquiring nuclear magnetic resonance (NMR) measurements of the rock sample;

generating, based on NMR imaging, a fluid distribution profiles, the fluid distribution profiles representing a movement of a fluid front; and

obtaining, based on NMR imaging, a quantification of fracture volume, the quantification of the fracture volume representing the amount of the fluid in a fracture.

19. The non-transitory computer readable medium of claim 18 , further comprising:

identifying a presence of fractures in a rock sample by measuring movement of fluid through the rock sample over time;

predicting an extent of the fractures in the rock sample by determining fluid distribution profiles of the fluid; and

quantifying the fracture volume through a measurement of peak volumes in NMR spectra.

20. The non-transitory computer readable medium according to claim 18 , further comprising:

generating, by inversion of the NMR measurements, a spatial transverse relaxation time (T 2 ) distribution; and

generating, based on the spatial T 2 distribution, the saturation profile representing distribution of the fluid stored in the rock sample.