Methods for determining wettability from NMR

Patent metadata

Field	Value
Publication number	US-9405037-B2
Application number	US-201313854183-A
Country	US
Kind code	B2
Filing date	Apr 1, 2013
Priority date	Apr 2, 2012
Publication date	Aug 2, 2016
Grant date	Aug 2, 2016

Abstract

Methods are described for wettability characterization based on NMR measurements, which are sensitive to the surface wetting conditions of oil and water at the pore scale. The described methods make use of surface relaxation effects on the NMR relaxation (T 2 ). Workflows are described to obtain wettability profiles of a porous media such as a rock either in the native state or prepared to a certain state in the laboratory. An underlying forward model is also described for the mixed wet and fractionally saturated pore spectrum. Outputs of the described inversion include continuous saturation and wettability profiles as a function of the pore sizes in the porous media, as well as an averaged value for saturation and wettability over the entire pore spectrum.

First claim

What is claimed is:

1. A method for characterizing wettability of a porous media, the method comprising:
Receiving pore size distribution data representing a distribution of pore sizes within the porous media;
Receiving nuclear magnetic resonance (NMR) data from a bulk aqueous fluid;
Receiving nuclear magnetic resonance (NMR) data from a bulk oil; and
performing an inversion on the nuclear magnetic resonance (NMR) data using a forward model for pore level distribution of wettability and saturation in mixed wet conditions over a plurality of pore sizes using the pore size distribution data and the nuclear magnetic resonance (NMR) data for the bulk aqueous fluid and bulk oil, thereby generating a wettability profile across a pore spectrum for the aqueous and/or oil fluids over a plurality of pore sizes of the porous media.

2. The method according to claim 1 , wherein the nuclear magnetic resonance (NMR) data is nuclear magnetic resonance (NMR) echo train data and the inversion is performed in the time domain.

3. The method according to claim 1 , wherein the NMR data is of a type selected from a group consisting of: Car-Purcell-Miniboom-Gill (CPMG), diffusion editing, T 1 -T 2 , T 2 , T 2 -T 2 , D-T 1 and D-T 2 , where T1 is a longitudinal relaxation time, T2 is a transverse relaxation time, and D is an indication of diffusion.

4. The method according to claim 1 , wherein the forward model includes a function for saturation that is non-monotonically increasing or decreasing along a spectrum of pore sizes.

5. The method according to claim 1 , wherein the performing of the inversion includes using a grid search method for the inversion.

6. The method according to claim 1 , wherein the performing of the inversion includes mathematically constraining saturation values across a plurality of pore sizes in the forward model.

7. The method according to claim 6 , wherein the saturation values are constrained based at least in part on a known saturation history of the porous media.

8. The method according to claim 7 , wherein the porous media was originally strongly oil-wet and then flooded with the aqueous fluid, the water saturation is constrained to be monotonically increasing with increasing pore size.

9. The method according to claim 7 , wherein the porous media was originally strongly water-wet and then flooded with oil, the water saturation is constrained to be monotonically decreasing with increasing pore size.

10. The method according to claim 7 , wherein the porous media has experienced an oil flooding and water flooding event, the water saturation is constrained to a Gaussian profile.

11. The method according to claim 7 , wherein the saturation history is known by virtue of a saturation technique selected from a group consisting of: core flooding, core centrifuge, reservoir management, water flooding history, and production history.

12. The method according to claim 7 , wherein a saturation index is obtained from an independent measurement, and an overall water saturation S NMR is constrained to be within a fixed range of the independent measurement.

13. The method according to claim 6 , wherein the saturation is known by injecting a paramagnetic fluid into the porous media.

14. The method according to claim 1 , wherein the performing of the inversion includes mathematically constraining the forward model using data derived from nuclear magnetic resonance (NMR) data.

15. The method according to claim 14 , wherein data is derived using a Mellin transform.

16. The method according to claim 1 , wherein in the performing of the inversion further generates a saturation profile across a pore spectrum.

17. The method according to claim 16 , further comprising determining overall wettability by integrating the wettability profile weighted by the pore size distribution data; and determining overall saturation by integrating the saturation profile weighted by the pore size distribution data.

18. The method according to claim 16 , further comprising displaying to a user said wettability and saturation profiles as a function of pore size distribution.

19. The method according to claim 1 , wherein the porous media is a core sample from a subterranean hydrocarbon-bearing rock formation.

20. The method according to claim 1 , wherein the pore size distribution data is obtained using a technique selected from a group consisting of: nuclear magnetic resonance (NMR) T 2 pore size distribution; mercury intrusion; and x-ray tomography.

21. A system for characterizing wettability of a porous media, the system comprising:
an nuclear magnetic resonance (NMR) measurement system adapted and configured to make nuclear magnetic resonance (NMR) measurements of a bulk aqueous fluid and a bulk oil, and to generate therefrom nuclear magnetic resonance (NMR) data; and
a processing system programmed and configured to perform an inversion on the nuclear magnetic resonance (NMR) data using a forward model for pore level distribution of wettability and saturation in mixed wet conditions over a plurality of pore sizes using a pore size distribution of the porous media, and the nuclear magnetic resonance (NMR) data, thereby generating a wettability profile across a pore spectrum for the aqueous fluid over a plurality of pore sizes of the porous media.

22. The system according to claim 21 , wherein the nuclear magnetic resonance (NMR) data is echo train data and the inversion is performed in the time domain.

23. The system according to claim 21 , wherein the porous media is a core sample from a subterranean hydrocarbon-bearing formation.

24. The system according to claim 23 , further comprising a core sampling tool deployable in a wellbore configured to obtain a core samples from the subterranean formation.

25. The system according to claim 21 , wherein at least part of the nuclear magnetic resonance (NMR) measurement system is adapted to be deployed downhole so as to make the nuclear magnetic resonance (NMR) measurements of the bulk aqueous fluid and/or bulk oil downhole while the fluid is in a live state.

26. The system according to claim 21 , wherein the inversion on the nuclear magnetic resonance (NMR) data further generates a saturation profile across the pore spectrum and wherein the processing system is further configured to displaying to a user said wettability and saturation profiles as a function of pore size distribution.

27. A method for characterizing wettability of a porous media by a first fluid in the presence of a second fluid, the method comprising:
receiving nuclear magnetic resonance (NMR) data from the first and the second bulk fluids;
receiving pore size distribution data representing a distribution of pore sizes within the porous media; and
performing an inversion process in the time domain using the nuclear magnetic resonance (NMR) data using a forward model for pore level distribution of wettability and saturation in mixed wet conditions over a plurality of pore sizes using the pore size distribution data and the nuclear magnetic resonance (NMR) each train data, thereby generating a wettability profile across a pore spectrum for the first fluid over a plurality of pore sizes of the porous media.

28. The method according to claim 27 , wherein nuclear magnetic resonance (NMR) data is nuclear magnetic resonance (NMR) echo train data and the inversion process is performed in th

Assignees

• Al-Muthana Ahmed
• Hursan Gabor
• Ma Shouxiang
• Singer Philip M
• Nicot Benjamin
• Valori Andrea
• Ali Farhan
• Bachman Henry N
• Schlumberger Technology Corp
• Saudi Aramco

Inventors

• Al-Muthana Ahmed
• Hursan Gabor
• Ma Shouxiang
• Singer Philip M
• Nicot Benjamin
• Valori Andrea
• Ali Farhan
• Bachman Henry N

Classifications

• G01V3/14

  operating with electron or nuclear magnetic resonance · CPC title

• G01N24/081 Primary

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

• G01V3/38 Primary

  Processing data, e.g. for analysis, for interpretation, for correction · CPC title