Determination of shale content of formation from dispersive multi-frequency dielectric measurements

Patent metadata

Field	Value
Publication number	US-10649110-B2
Application number	US-201615374419-A
Country	US
Kind code	B2
Filing date	Dec 9, 2016
Priority date	Dec 9, 2016
Publication date	May 12, 2020
Grant date	May 12, 2020

Abstract

Methods and apparatus for evaluating a volume of an earth formation wherein the volume comprises a fluid-saturated rock matrix including clay particles. Methods include making measurements of complex permittivity at a plurality of frequencies using an electromagnetic tool in a borehole penetrating the earth formation; and estimating a plurality of parameters of interest simultaneously using the measurements at the plurality of frequencies and a mixing model accounting for electrical effects on the measurements caused by the clay particles. The plurality may include at least: i) water saturation; and ii) resistivity of formation water. Parameters of interest may comprise at least one of: i) an electrical parameter of the volume; and ii) a textural parameter of the volume. Methods may include modeling for electrical effects caused by at least one of: i) a surface conductivity of the clay particles; and ii) a textural property of the clay particles.

First claim

What is claimed is:

1. A method of evaluating a volume of an earth formation wherein the volume comprises a fluid-saturated rock matrix including clay particles, the method comprising:
making measurements of complex permittivity at a plurality of frequencies using an electromagnetic tool in a borehole penetrating the earth;
estimating a plurality of parameters of interest simultaneously by performing an inversion using the measurements at the plurality of frequencies and a mixing model accounting for electrical effects on the measurements caused by the clay particles wherein the mixing model relates the effective permittivity of the volume to a function of the corresponding permittivity of each of a plurality of components of the volume, the function of the corresponding permittivity of each of the plurality of components of the volume comprising a root of degree C EXP applied to the corresponding permittivity of each of the plurality of components, where C EXP is constrained to be a positive rational number, the plurality of parameters comprising a value for C EXP generated as output from the inversion and at least one of: i) water saturation; and ii) resistivity of formation water.

2. The method of claim 1 comprising modeling for electrical effects caused by at least one of: i) a surface conductivity of the clay particles; and ii) a textural property of the clay particles.

3. The method of claim 1 wherein the plurality of parameters comprises at least one of: i) an additional electrical parameter of the volume; and ii) a textural parameter of the volume.

4. The method of claim 1 , wherein the mixing model is derived from a relationship of an effective permittivity of the volume to a corresponding volumetric factor and a corresponding permittivity of each of a plurality of components of the volume.

5. The method of claim 4 , wherein the components comprise at least formation water and at least one of: i) the rock matrix of the formation; and ii) formation hydrocarbons.

6. The method of claim 5 , wherein the plurality of parameters comprises a volumetric factor for at least the formation water and at least one of: i) the rock matrix of the formation; and ii) the formation hydrocarbons.

7. The method of claim 1 , further comprising:
using at least one processor to estimate an effective permittivity and an effective conductivity of the volume.

8. The method of claim 7 , further comprising:
estimating the at least one parameter of interest in dependence upon the effective permittivity; the effective conductivity; an estimated porosity; and an estimated temperature.

9. The method of claim 8 , further comprising:
estimating a permittivity of a rock matrix within the volume using at least one of: i) lithology information, and ii) a volumetric analysis of the volume.

10. The method of claim 1 wherein the at least one parameter of interest comprises at least one of: i) cation exchange capacity (CEC);
ii) a textural parameter of the clay particles; iii) permittivity of formation water; iv) clay type of clay particles.

11. The method of claim 4 , wherein the model relates dispersion between the measurements to the plurality of parameters of interest.

12. The method of claim 1 , wherein the plurality of parameters of interest comprise resistivity of formation water, water saturation, and permittivity of the rock matrix; and wherein estimating the plurality of parameters of interest comprises using the measurements to perform an inversion for a value of the resistivity of formation water, a value of the water saturation, a value of the permittivity of the rock matrix, and a value of the C EXP simultaneously.

13. The method of claim 1 , further comprising using a stochastic correlation library correlating the plurality of parameters of interest to a property of the clay particles to estimate the property.

14. The method of claim 1 , further comprising:
conveying the electromagnetic tool in the borehole.

15. The method of claim 1 , wherein the electromagnetic tool uses electrical induction.

16. The method of claim 1 , wherein estimating the plurality of parameters of interest comprises using measurements from five different frequencies in an inversion.

17. An apparatus for evaluating a volume of an earth formation wherein the volume comprises a fluid-saturated rock matrix including clay particles, the apparatus comprising:
a carrier configured to be conveyed in a borehole penetrating the earth formation;
an electromagnetic tool disposed on the carrier and configured to make measurements of complex permittivity of a volume of the earth formation proximate the tool at a plurality of frequencies; and
at least one processor configured to:
estimating a plurality of parameters of interest simultaneously by performing an inversion using the measurements at the plurality of frequencies and a mixing model accounting for electrical effects on the measurements caused by the clay particles, wherein the mixing model relates the effective permittivity of the volume to a function of the corresponding permittivity of each of a plurality of components of the volume, the function of the corresponding permittivity of each of the plurality of components of the volume comprising a root of degree C EXP applied to the corresponding permittivity of each of the plurality of components, where C EXP is constrained to be a positive rational number, the plurality of parameters comprising a value for CEXP generated as output from the inversion and at least one of: i) water saturation; and ii) resistivity of formation water.

Assignees

• Baker Hughes Inc
• Baker Hughes A Ge Co Llc

Inventors

• Zhang Yinxi

Classifications

• G01V3/28 Primary

  using induction coils · CPC title

• G01N27/22 Primary

  by investigating capacitance · CPC title

• G01V3/38 Primary

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

• G01V3/30

  operating with electromagnetic waves · CPC title

• G01N33/24

  Earth materials (G01N33/42 takes precedence) · CPC title