Methods and systems for determining subterranean fracture closure

Patent metadata

Field	Value
Publication number	US-10267134-B2
Application number	US-201514942304-A
Country	US
Kind code	B2
Filing date	Nov 16, 2015
Priority date	Jan 4, 2013
Publication date	Apr 23, 2019
Grant date	Apr 23, 2019

Abstract

Methods and systems for determining subterranean fracture closure are disclosed herein. The methods can include electrically energizing a casing of a wellbore that extends from a surface of the earth into a subterranean formation having a fracture that is at least partially filled with an electrically conductive proppant and measuring a first electric field response at the surface or in an adjacent wellbore at a first time interval to provide a first field measurement. The methods can also include measuring a second electric field response at the surface or in the adjacent wellbore at a second time interval to provide a second field measurement and determining an increase in closure pressure on the electrically conductive proppant from a difference between the first and second field measurements.

First claim

What is claimed is:

1. A method for determining fracture closure, comprising:
electrically energizing a casing of a wellbore that extends from a surface of the earth into a subterranean formation having a fracture that is at least partially filled with an electrically conductive proppant;
measuring a first electric field response at the surface or in an adjacent wellbore at a first time interval to provide a first field measurement;
measuring a second electric field response at the surface or in the adjacent wellbore at a second time interval to provide a second field measurement; and
determining an increase in closure pressure on the electrically conductive proppant from a difference between the first and second field measurements.

2. The method of claim 1 , wherein measuring the first electric field response comprises measuring three dimensional (x, y, and z) components of electric and magnetic field responses.

3. The method of claim 2 , wherein measuring the second electric field response comprises measuring three dimensional (x, y, and z) components of electric and magnetic field responses.

4. The method of claim 3 , further comprising:
measuring three dimensional (x, y, and z) components of electric and magnetic field responses at the surface or in the adjacent wellbore at three or more time intervals to provide three or more field measurements; and
determining an increase in closure pressure on the electrically conductive proppant from differences between each of the three or more field measurements.

5. The method of claim 1 , further comprising:
injecting into the fracture the electrically conductive proppant and wherein the electrically conductive proppant includes electrically conductive sintered, substantially round and spherical particles; and
prior to the injecting of the electrically conductive proppant into the fracture, injecting a hydraulic fluid into the wellbore at a rate and pressure sufficient to open the fracture therein.

6. The method of claim 3 , wherein the measuring of the three dimensional (x, y, and z) components of electric and magnetic field responses at the surface or in an adjacent wellbore comprises measuring the three dimensional (x, y, and z) components of electric and magnetic field responses using an array of sensors distributed at or near the surface and at least partially over the fracture.

7. The method of claim 1 , wherein the increase in closure pressure on the electrically conductive proppant increases the electrical conductivity of the electrically conductive proppant by at least about 50%.

8. The method of claim 4 , further comprising determining a closure of the fracture by observing substantially no difference between two successive field measurements.

9. The method of claim 1 , wherein, numerical simulations, solving Maxwell's equations of electromagnetism for the electric and magnetic fields are performed, prior to obtaining the first field measurement, to determine temporal characteristics of an optimum input wave form and a recording sensor array geometry to be used in the field applications, wherein the numerical simulations are based upon an earth model determined from geophysical logs and geological information.

10. A method for determining fracture closure time, comprising:
introducing a first electric current to a subterranean formation extending from a wellbore;
obtaining a first measurement by measuring three dimensional (x, y, and z) components of electric and magnetic field responses from the first electric current at a surface of the earth or in an adjacent wellbore;
injecting a hydraulic fluid into the subterranean formation at a rate and pressure sufficient to open a fracture therein;
injecting into the fracture a fluid containing electrically conductive sintered, substantially round and spherical particles under a first pressure;
introducing a second electric current to the earth at or near the fracture containing the electrically conductive sintered, substantially round and spherical particles;
obtaining a second measurement by measuring three dimensional (x, y, and z) components of electric and magnetic field responses from the second electric current at a surface of the earth or in an adjacent wellbore;
releasing the first pressure;
introducing a third electric current to the earth at or near the fracture;
obtaining a third measurement by measuring three dimensional (x, y, and z) components of electric and magnetic field responses from the third electric current at a surface of the earth or in an adjacent wellbore; and
determining a difference between the first and second measurements.

11. The method of claim 10 , wherein the fracture is in an open state when the second measurement is obtained.

12. The method of claim 10 , further comprising:
introducing a series of discrete electric current injections (a 1 . . . a N ) to the earth at or near the fracture, wherein N is any integer greater than 3 and a 1 is the first electric current; and
obtaining discrete measurements (b 1 . . . b N ) for each of (a 1 . . . a N ) by measuring three dimensional (x, y, and z) components of electric and magnetic field responses from each of the (a 1 . . . a N ) electric current injections at a surface of the earth or in an adjacent wellbore, wherein b 1 is the first measurement.

13. The method of claim 12 , further comprising iteratively comparing measurements b N and b N+1 to check for differences between two successive measurements, wherein closure of the fracture is determined by observing no substantial difference between b N and b N+1 .

14. The method of claim 13 , wherein b N+1 is a final measurement when there is no observed substantial difference between b N and b N+1 and a fracture closure time is determined by calculating time accrued from injecting into the fracture the fluid containing electrically conductive sintered, substantially round and spherical particles under a first pressure to introducing electric current a N+1 .

15. The method of claim 10 , wherein the measured three dimensional components of the electric and magnetic field responses are analyzed with imaging methods selected from the group consisting of an inversion algorithm based on Maxwell's equations of electromagnetism and electromagnetic holography to determine a proppant pack location, wherein, in the inversion algorithm, parameters of an earth model are adjusted to obtain a fit to a plurality of forward model calculations of responses for an assumed earth model, and wherein, in the electromagnetic holography, the electric and magnetic field responses and a source wave form are projected into an earth volume to form an image of the proppant pack location using constructive and destructive interferences.

16. The method of claim 10 , wherein electromagnetic wave forms selected from the group consisting of Gaussian, square and time domain are used as an input signal to generate the three dimensional electric field and magnetic field responses.

17. The method of claim 15 , wherein, numerical simulations, solving Maxwell's equations of electromagnetism for the electric and magnetic fields are performed, prior to field applications, to determine temporal characteristics of an optimum input wave form and a recording sensor array geometry to be used in the field applications, wherein the numerical simulations are based upon an earth model determined from geophysical logs and geological information.

18. A method for determining fracture closure time, comprising:
introducing a first electric current to a subterr

Assignees

• Carbo Ceramics Inc
• Sandia Corp

Inventors

• Cannan Chad
• Bartel Lewis
• Palisch Terry
• Aldridge David
• Roper Todd
• Savoy Steve
• Mitchell Daniel R

Classifications

• E21B43/267 Primary

  reinforcing fractures by propping · CPC title