Petrographic image analysis for determining capillary pressure in porous media

1. A method for characterizing a sample of porous media including a plurality of pore bodies and a plurality of pore throats, the method comprising:

preparing the sample of the porous media such that a single plane of the sample can be imaged;

generating a two-dimensional high resolution image of the single plane of the prepared sample of the porous media;

processing the high resolution image in part by carrying out a watershed image processing technique;

identifying a plurality of pore throats based at least in part on the watershed technique; and

determining a dimension associated with each of the identified plurality of pore throats and

wherein the processing is carried out with a processing system.

2. A method according to claim 1 wherein the high resolution image is made using confocal microscopy.

3. A method according to claim 2 wherein the high resolution image is made using laser scanning fluorescence microscopy.

4. A method according to claim 2 wherein a depth of field of the high resolution image is less than 0.4 microns.

5. A method according to claim 1 wherein the porous media is a rock sample.

6. A method according to claim 5 wherein the preparing includes subjecting the sample of porous media to vacuum-pressure impregnation with fluorescing epoxy.

7. A method according to claim 5 wherein the preparing includes cutting the sample of porous media into a thin slice of less than about 100 microns thickness.

8. A method according to claim 5 wherein the preparing includes cutting the sample of porous media into a thick slice of greater than about 2000 microns thickness.

9. A method according to claim 1 wherein the porous media is a subterranean rock formation.

10. A method according to claim 9 wherein the subterranean rock formation is hydrocarbon bearing.

11. A method according to claim 10 wherein the porous media is a core sample from the rock formation.

12. A method according to claim 1 wherein the watershed technique includes simulated flooding.

13. A method according to claim 1 further comprising determining pore-body and pore-throat size distributions and capillary pressure curves in the porous media based at least in part on the watershed technique.

14. A method according to claim 1 wherein the processing includes one or more pre-processing and enhancement techniques selected from a group consisting of: stitching, registration, blending, clipping and rotation.

15. A method according to claim 1 wherein the processing includes segmenting the high resolution image into grains and pores, thereby generating a binary image.

16. A method according to claim 15 wherein a porosity value from an analysis of the porous media is used to control a threshold in the segmentation.

17. A method according to claim 15 wherein a binary image is separated into a pores image and a throats image using one or more binary logical operations.

18. A method according to claim 17 wherein the pores image and throats image are differentiated using one or more clustering algorithms thereby generating a clustered pores image and a clustered throats image, and pore-body and pore-throat size distributions are computed based on clustered images.

19. A method according to claim 18 wherein the clustered pores image and throats image are subjected to data analysis wherein each pore body is assigned a diameter of a largest pore throat connected to the pore body, and each pore body has a known pore area, and pores having at least one connected throat are binned according to largest throat size, and pore-body size for each bin is computed and used to generate simulated capillary pressure curves using a Washburn equation.

20. A method according to claim 1 wherein the sample of the porous media is two-dimensional.

21. A method according to claim 1 wherein the sample of the porous media is three-dimensional.

22. A system for characterizing a sample of porous media including a plurality of pore bodies and a plurality of pore throats, the system comprising:

a sample preparation system adapted to prepare a sample of the porous media such that a single plane of the sample can be imaged;

an imaging system adapted to generate a two-dimensional high resolution image of a single plane of a prepared sample of the porous media; and

a processing system adapted and programmed to process a generated two-dimensional high resolution image in part by carrying out a watershed image processing technique, to identify a plurality of pore throats based at least in part on the watershed technique; and to determine a dimension associated with each of the identified plurality of pore throats.

23. A system according to claim 22 further comprising a sample collection system adapted to collect a sample of the porous media.

24. A system according to claim 23 wherein the porous media is a hydrocarbon bearing subterranean rock formation, and the sample collection system includes a core-sampling tool.

25. A system according to claim 22 wherein the imaging system uses laser scanning fluorescence microscopy.

26. A system according to claim 22 wherein the processing system is further adapted and programmed to determine pore-body and pore-throat size distributions and capillary pressure curves in the porous media based at least in part on the watershed technique.

27. A method for characterizing a sample of porous subterranean rock formation including a plurality of pore bodies and a plurality of pore throats, the method comprising:

preparing the sample of porous subterranean rock formation such that a single plane of the sample can be imaged;

generating a two-dimensional high resolution image of the single plane of the prepared sample of the rock using laser scanning fluorescence microscopy;

segmenting the high resolution image into grains and pores, thereby generating a binary image processing the binary image by carrying out a watershed image processing technique;

identifying a plurality of pore throats based at least in part on the watershed technique; and

determining a throat length dimension associated with each of the identified plurality of pore throats, and

determining pore-body and pore-throat size distributions and capillary pressure curves in the porous media based at least in part on the watershed technique.

28. A method according to claim 27 wherein the porous rock formation is a hydrocarbon bearing subterranean rock formation.

29. A method according to claim 27 wherein a porosity value from an analysis of the porous rock is used to control a threshold in the segmenting.