Technique for determining properties of earth formations using dielectric permittivity measurements

• US 20070061082A1
• Filed: 09/23/2005
• Published: 03/15/2007
• Est. Priority Date: 09/12/2005
• Status: Active Grant

• Current Assignee: Schlumberger Technology Corporation (Schlumberger NV)
• Original Assignee: Schlumberger Technology Corporation (Schlumberger NV)
• Inventors: Habashy, Tarek, Seleznev, Nikita, Boyd, Austin, Hizem, Mehdi
• Granted Patent: US 7,363,160 B2
• Time in Patent Office: Days
• US Class Current: 702/11
• CPC Class Codes: G01V 3/26 operating with magnetic or electric fields produced or modified either by the surrounding earth formation or by the detecting device with electromagnetic waves G01V3/30
• CPC Class Codes: G01V 3/30 operating with electromagnetic waves
• CPC Class Codes: Y02A 90/30 Assessment of water resources

Abstract

Techniques for determining formation characteristics use measurements of dielectric permittivity at a number of frequencies. Determined characteristics include the vertical and horizontal formation dielectric constant and conductivity, the formation water conductivity, the water saturation, the cementation and the saturation exponents. In laminated formations these profiles can be determined for each lamina. Also, formation dielectric properties are used in determination of the rock type.

Claims

1. A method for determining the cementation and the saturation exponent of earth formations surrounding a borehole, comprising the steps of:

deriving, from measurements of electromagnetic energy in said formations, at a plurality of frequencies, a respective plurality of formation permittivities and a respective plurality of formation conductivities; and

determining, using said plurality of formation permittivities and formation conductivities, the cementation and the saturation exponent of said formations.

2. The method as defined by claim 1, wherein said plurality of frequencies comprises two frequencies.

3. The method as defined by claim 1, wherein said plurality of frequencies comprises at least three frequencies.

4. The method as defined by claim 1, wherein said step of determining, using said plurality of formation permittivities and formation conductivities, the cementation and the saturation exponent of said formations, includes the following steps:

determining, using said plurality of formation permittivities and formation conductivities, the formation water saturation and the formation DC resistivity;

selecting a further water saturation and deriving a corresponding further DC resistivity; and

determining said cementation and said saturation exponent using said formation water saturation, said further water saturation, said formation DC resistivity, and said further DC resistivity.

5. The method as defined by claim 4, further comprising the steps of deriving the permittivities of the formation matrix and hydrocarbons, and the formation water salinity, and using said derived permittivities of the formation matrix and hydrocarbons and said derived water salinity in said steps of determining said formation water saturation and formation DC resistivity and said further DC resistivity.

6. The method as defined by claim 5, further comprising the step of deriving aspect ratios associated with the formation matrix, and using said aspect ratios in determining said formation water saturation and formation DC resistivity and said further DC resistivity.

7. The method as defined by claim 3, wherein said step of determining, using said plurality of formation permittivities and formation conductivities, the cementation and the saturation exponent of said formations, includes the following steps:

determining, using said plurality of formation permittivities and formation conductivities, the formation water saturation and the formation DC resistivity;

selecting a further water saturation and deriving a corresponding further DC resistivity; and

determining said cementation and said saturation exponent using said formation water saturation, said further water saturation, said formation DC resistivity, and said further DC resistivity.

8. The method as defined by claim 6, wherein said step of determining, using said plurality of formation permittivities and formation conductivities, the formation water saturation and the formation DC resistivity, includes the following steps:

inverting, using a dispersion model and said plurality of formation permittivities and formation conductivities, to obtain said formation water saturation;

deriving, using said plurality of formation permittivities and formation conductivities, and said obtained formation water saturation, a formation conductivity dispersion curve; and

determining, from said formation conductivity dispersion curve, the formation DC resistivity.

9. The method as defined by claim 7, wherein said step of determining, using said plurality of formation permittivities and formation conductivities, the formation water saturation and the formation DC resistivity, includes the following steps:

inverting, using a dispersion model and said plurality of formation permittivities and formation conductivities, to obtain said formation water saturation;

deriving, using said plurality of formation permittivities and formation conductivities, and said obtained formation water saturation, a formation conductivity dispersion curve; and

determining, from said formation conductivity dispersion curve, the formation DC resistivity.

10. The method as defined by claim 9, wherein said step of inverting, using a dispersion model and said plurality of formation permittivities and formation conductivities, is operative to further obtain the salinity of the formation water and the permittivity of the formation matrix.

11. The method as defined by claim 8, wherein said step of inverting, using a dispersion model and said plurality of formation permittivities and formation conductivities, is operative to further obtain rock texture parameters of the formation matrix.

12. The method as defined by claim 9, wherein said step of inverting, using a dispersion model and said plurality of formation permittivities and formation conductivities, is operative to further obtain rock texture parameters of the formation matrix.

13. The method as defined by claim 12, wherein said rock texture parameters comprise aspect ratios of rock grains of the formation matrix.

14. The method as defined by claim 12, wherein said rock texture parameters comprise spherical grains and ellipsoidal micropores of the formation matrix.

15. The method as defined by claim 12, wherein said rock texture parameters comprise aspect ratios of macropores, grains, and hydrocarbons.

16. The method as defined by claim 1, wherein at least some of said measurements of electromagnetic energy in said formations are taken at different depths of investigation.

17. The method as defined by claim 1, wherein at least some of said measurements of electromagnetic energy in said formations are taken at different depths of investigation, and wherein said step of determining the cementation and the saturation exponent of said formations comprises determining a radial profile of at least one of said cementation and said saturation exponent.

18. The method as defined by claim 9, wherein at least some of said measurements of electromagnetic energy in said formations are taken at different depths of investigation, and wherein said step of inverting to obtain said formation water saturation comprises inverting to obtain a radial profile of formation water saturation.

19. The method as defined by claim 10, wherein at least some of said measurements of electromagnetic energy in said formations are taken at different depths of investigation, and wherein said step of inverting to obtain said formation water salinity comprises inverting to obtain a radial profile of formation water salinity.

20. The method as defined by claim 1, wherein at least some of said measurements of electromagnetic energy in said formations are taken at different polarizations, and wherein said step of determining the cementation and the saturation exponent of said formations comprises determining a radial profile of at least one of said cementation and said saturation exponent.

21. The method as defined by claim 9, wherein at least some of said measurements of electromagnetic energy in said formations are taken at different polarizations, and wherein said step of inverting to obtain said formation water saturation comprises inverting to obtain a radial profile of formation water saturation.

22. The method as defined by claim 10, wherein at least some of said measurements of electromagnetic energy in said formations are taken at different polarizations, and wherein said step of inverting to obtain said formation water salinity comprises inverting to obtain a radial profile of formation water salinity.

23. The method as defined by claim 1, wherein said plurality of frequencies are in the range about 100 MHz to 1 GHz.

24. A method for determining a radial profile of permittivity and/or conductivity of anisotropic earth formations surrounding a borehole, comprising the steps of:

deriving, from measurements of electromagnetic energy in said formations, at a plurality of frequencies, and at different depths of investigation, a respective plurality of formation permittivities and a respective plurality of formation conductivities; and

determining, using said plurality of formation permittivities and formation conductivities, a radial profile of vertical and horizontal permittivity and/or a radial profile of vertical and horizontal conductivity.

25. A method for determining a radial profile of permittivity and/or conductivity of anisotropic earth formations surrounding a borehole, comprising the steps of:

deriving, from measurements of electromagnetic energy in said formations, at a plurality of frequencies, and at different polarizations, a respective plurality of formation permittivities and a respective plurality of formation conductivities; and

determining, using said plurality of formation permittivities and formation conductivities, a radial profile of vertical and horizontal permittivity and/or a radial profile of vertical and horizontal conductivity.

26. A method for determining effective permittivity of earth formations surrounding a borehole, comprising the steps of:

deriving a mixing law permittivity as volumetric fractions of formation matrix, water, and hydrocarbon permittivities;

deriving an effective permittivity model as a function of mixing law permittivity and rock texture parameters;

deriving, from measurements of electromagnetic energy in said formations, at a plurality of frequencies, a respective plurality of formation permittivities and a respective plurality of formation conductivities; and

determining effective permittivity of said formations using said model and said derived plurality of formation permittivities and formation conductivities.

27. The method as defined by claim 26, wherein said rock texture parameters comprise aspect ratios of rock grains of the formation matrix.

28. The method as defined by claim 26, wherein said rock texture parameters comprise spherical grains and ellipsoidal micropores of the formation matrix.

29. The method as defined by claim 26, wherein said rock texture parameters comprise aspect ratios of macropores, grains, and hydrocarbons.

30. A method for determining rock type of earth formations surrounding a borehole, comprising the steps of:

deriving a mixing law permittivity as volumetric fractions of formation matrix, water, and hydrocarbon permittivities;

deriving an effective permittivity model as a function of mixing law permittivity and rock texture parameters;

deriving, from measurements of electromagnetic energy in said formations, at a plurality of frequencies, a respective plurality of formation permittivities and a respective plurality of formation conductivities; and

determining rock type of said formations using said model and said derived plurality of formation permittivities and formation conductivities.