Hydraulic fracture characterization using borehole sonic data

Patent metadata

Field	Value
Publication number	US-9476998-B2
Application number	US-201113992752-A
Country	US
Kind code	B2
Filing date	Dec 16, 2011
Priority date	Dec 21, 2010
Publication date	Oct 25, 2016
Grant date	Oct 25, 2016

Abstract

A method and apparatus for assessing induced fractures in a subterranean formation including acquiring sonic data before and after a hydraulic fracturing operation, calculating a shear modulus in the borehole cross-sectional plane from Stoneley data, and calculating two shear moduli in two borehole orthogonal axial planes from cross dipole data. A method and apparatus for assessing induced fractures in a subterranean formation including collecting sonic data before and after fracturing the formation, calculating a far-field shear modulus in the borehole cross-sectional plane and a far-field shear moduli in the two orthogonal borehole axial planes, inferring the open or closed status of a fracture, and estimating a radial width or height or both of a vertical fracture.

First claim

What is claimed is:

1. A method for assessing induced fractures in a subterranean formation, comprising:
providing a sonic tool in a borehole surrounded by the subterranean formation, wherein the sonic tool comprises an acoustic source and a plurality of receivers;
transmitting a sonic signal by the acoustic source before and after a hydraulic fracturing operation;
acquiring sonic data by the plurality of receivers before and after the hydraulic fracturing operation, wherein the sonic data comprises Stoneley data and cross dipole data;
calculating a shear modulus in a borehole cross-sectional plane from the Stoneley data;
calculating two shear moduli in two orthogonal borehole axial planes from the cross dipole data;
estimating changes in the shear modulus and the two shear moduli; and
outputting the changes in the shear modulus and the two shear moduli to assess the induced fractures,
wherein the borehore is a cased hole, and
wherein the method further comprises using an algorithm that accounts for a distortion of a steel casing that is bonded with the formation through a cement annulus.

2. The method of claim 1 , further comprising using an algorithm that accounts for a distortion of a sonic tool structure.

3. The method of claim 1 , further comprising converting the moduli into a compressional modulus along the borehole axis.

4. The method of claim 1 , further comprising converting the moduli into three shear moduli in the two orthogonal borehole axial planes and the borehole cross-sectional plane.

5. A method for assessing induced fractures in a subterranean formation, comprising:
providing a sonic tool in a borehole surrounded by the subterranean formation, the sonic tool comprising an acoustic source and a plurality of receivers;
transmitting a sonic signal by the acoustic source before and after fracturing;
collecting sonic data before and after fracturing the formation wherein the sonic data comprises Stoneley data and cross dipole data;
calculating a far-field shear modulus in a borehole cross-sectional plane and a far-field shear moduli in two orthogonal borehole axial planes from the Stoneley data and the cross dipole data;
inferring open or closed status of a fracture from the far-field shear moduli in the borehole cross-sectional plane and two orthogonal borehole axial planes;
estimating a radial width or height or both of a vertical fracture from the Stoneley data and the cross dipole data; and
outputting the radial width or height or both of the vertical fracture to assess the induced fractures.

6. The method of claim 5 , wherein the collecting comprises recording low-frequency monopole waveforms to obtain a borehole Stoneley dispersion.

7. The method of claim 5 , wherein the collecting comprises recording high-frequency monopole waveforms to obtain a far-field compressional slowness.

8. The method of claim 5 , wherein the collecting comprises recording cross-dipole waveforms and processing them to obtain the fast-shear azimuth.

9. The method of claim 5 , wherein the calculating comprises rotating cross-dipole waveforms to obtain the fast-dipole and slow-dipole dispersions.

10. The method of claim 5 , wherein the calculating comprises processing the borehole Stoneley dispersion to obtain the far-field shear modulus in the borehole cross-sectional plane.

11. The method of claim 5 , wherein the calculating comprises processing the fast- and slow-dipole dispersions to obtain the far-field shear moduli in the two orthogonal borehole axial planes.

12. The method of claim 5 , wherein the calculating comprises estimating differences in the far-field compressional and the three shear moduli between the pre-frac and post-frac acquisitions.

13. The method of claim 5 , wherein the calculating comprises estimating the dominant fracture orientation in terms of relative magnitude of changes in the three shear moduli.

14. The method of claim 5 , wherein the calculating comprises estimating the fracture parameters in terms of the normal and tangential compliances.

15. The method of claim 5 , wherein the calculating comprises comparing radial profiles of cross-dipole shear slownesses before and after fracturing.

16. The method of claim 5 , wherein the calculating comprises estimating an increase in the radial alteration after fracturing as an indicator of radial extent of vertically aligned fractures.

17. The method of claim 5 , wherein the estimating comprises an axial extent of increase in the cross-dipole shear slowness dispersion.

18. The method of claim 5 , wherein the sonic data is open hole sonic data or cased hole sonic data.

Assignees

• Sinha Bikash K
• Schlumberger Technology Corp

Inventors

• Sinha Bikash K

Classifications

• G01V1/306 Primary

  for determining physical properties of the subsurface, e.g. impedance, porosity or attenuation profiles · CPC title

• G01V2210/6242

  Elastic parameters, e.g. Young, Lamé or Poisson · CPC title

• G01V2210/646

  Fractures · CPC title

• G01V1/284

  Application of the shear wave component and/or several components of the seismic signal · CPC title

• G01V1/50 Primary

  Analysing data · CPC title