Detection and characterization of thin weak bedding planes in hydrocarbon-bearing laminated formations

Patent metadata

Field	Value
Publication number	US-10761064-B2
Application number	US-201615765460-A
Country	US
Kind code	B2
Filing date	Sep 30, 2016
Priority date	Oct 2, 2015
Publication date	Sep 1, 2020
Grant date	Sep 1, 2020

Abstract

Methods are provided for making, processing, and analyzing in situ measurements to indicate presence of thin bedding planes of weakness in a formation. Bedding planes as small as a few inches and smaller are identified using an ultrasonic borehole tool. In one embodiment, detected pseudo-Rayleigh waveforms are processed to determine whether multiple events are detected. If so, lamination and a likely bedding plane of weakness are identified. In another embodiment, a sonic borehole tool is run in conjunction with the ultrasonic borehole tool. Indications of shear and pseudo-shear wave speeds are compared, and where different, a bedding plane of weakness is identified. In another embodiment, a microresistivity imager is run with the ultrasonic borehole tool, and at locations where multiple events are not detected, the image obtained by the imager is inspected to find locations of sharp contrast with adjacent locations to thereby identify bedding planes of weakness.

First claim

What is claimed is:

1. A method of investigating a formation traversed by a borehole, the method comprising:
exciting and detecting pseudo-Rayleigh surface wave waveforms at a plurality of locations in the borehole using an ultrasonic borehole tool that includes an ultrasonic transmitter and at least one ultrasonic receiver in a pitch-catch mode;
determining at each of the plurality of locations in the borehole whether at least two events are represented in the pseudo-Rayleigh wave waveforms.

2. The method of claim 1 , further comprising:
if at least two events are represented at a particular location of the plurality of locations, identifying the particular location as a location of interfacial weakness in the formation.

3. The method of claim 2 , further comprising:
determining a time delay between the at least two events; and
associating a magnitude of the time delay with an extent of weakness.

4. The method of claim 3 , wherein the determining includes generating a signal envelope having at least two peaks, wherein the time delay is a delay between the at least two peaks in the envelope.

5. The method of claim 1 , wherein the at least one ultrasonic receiver comprises a near ultrasonic receiver and a far ultrasonic receiver, wherein the near ultrasonic receiver and the far ultrasonic receiver are spaced at different distances from the ultrasonic transmitter.

6. The method of claim 5 , wherein the determining comprises using deconvolution to process the pseudo-Rayleigh wave waveforms from the near ultrasonic receiver.

7. The method of claim 5 , wherein the determining comprises using spectral amplitude estimation to process the pseudo-Rayleigh wave waveforms from the near ultrasonic receiver.

8. The method of claim 5 , wherein the detecting includes determining that a signal is comprised of a plurality of sinusoids.

9. The method of claim 1 , further comprising:
exciting and detecting sonic shear wave waveforms and sonic compressional wave waveforms at the plurality of locations in the borehole using a sonic borehole tool that includes a sonic source and a plurality of sonic wave detectors;
exciting and detecting ultrasonic compressional wave waveforms at the plurality of locations in the borehole using the ultrasonic borehole tool;
determining shear wave slowness at the plurality of locations in the borehole using the sonic shear wave waveforms;
determining sonic compressional wave slowness at the plurality of locations in the borehole using the sonic compressional wave waveforms;
determining pseudo-shear wave slowness at the plurality of locations in the borehole using the pseudo-Rayleigh wave waveforms;
determining ultrasonic compressional wave slowness at the plurality of locations in the borehole using the ultrasonic compressional wave waveforms;
at each of the plurality of locations, comparing the shear wave slowness with the pseudo-shear wave slowness; and
at each of the plurality of locations, comparing the sonic compressional wave slowness with the ultrasonic compressional wave slowness.

10. The method of claim 9 , further comprising:
if (i) the shear wave slowness and the pseudo-shear wave slowness are different and (ii) the sonic compressional wave slowness and the ultrasonic compressional wave slowness agree at a particular of the plurality of locations, identifying the particular location as a location of interfacial weakness in the formation.

11. The method of claim 10 , further comprising:
determining a difference between the shear wave slowness and the pseudo-shear wave slowness; and
associating a magnitude of the difference with an extent of interfacial weakness.

12. The method of claim 1 , further comprising:
imaging the borehole at the plurality of locations using a microresistivity borehole scanner tool that includes an array of electrodes;
processing signals from the array of electrodes to generate an image of the borehole at the plurality of locations in the borehole;
if at least two events are not represented for any particular location, using the microresistivity image to identify whether that location presents a sharp contrast in resistivity relative to adjacent locations, and if so, identifying the particular location as a location of interfacial weakness in the formation.

13. The method of claim 12 , wherein the processing signals from the array of electrodes to generate an image of the borehole at the plurality of locations comprises generating the image using a dynamic scale.

14. A method of investigating a formation traversed by a borehole, the method comprising:
exciting and detecting sonic shear wave waveforms and sonic compressional wave waveforms at a plurality of locations in the borehole using a sonic borehole tool that includes a sonic source and a plurality of sonic wave detectors;
exciting and detecting pseudo-Rayleigh surface wave waveforms and ultrasonic compressional wave waveforms at the plurality of locations in the borehole using an ultrasonic borehole tool that includes an ultrasonic transmitter and at least one ultrasonic receiver in a pitch-catch mode;
determining shear wave slowness at the plurality of locations in the borehole using the sonic shear wave waveforms;
determining sonic compressional wave slowness at the plurality of locations in the borehole using the sonic compressional wave waveforms;
determining pseudo-shear wave slowness at the plurality of locations in the borehole using the pseudo-Rayleigh wave waveforms;
determining ultrasonic compressional wave slowness at the plurality of locations in the borehole using the ultrasonic compressional wave waveforms;
at each of the plurality of locations, comparing the shear wave slowness with the pseudo-shear wave slowness;
at each of the plurality of locations, comparing the sonic compressional wave slowness with the ultrasonic compressional wave slowness; and
if (i) the shear wave slowness and the pseudo-shear wave slowness are different and (ii) the sonic compressional wave slowness and the ultrasonic compressional wave slowness agree at a particular location of the plurality of locations, identifying the particular location as a location of interfacial weakness in the formation.

15. The method of claim 14 , further comprising:
determining a difference between the shear wave slowness and the pseudo-shear wave slowness; and
associating a magnitude of the difference with an extent of interfacial weakness.

16. A method of investigating a formation traversed by a borehole, the method comprising:
exciting and detecting pseudo-Rayleigh surface wave waveforms at a plurality of locations in the borehole using an ultrasonic borehole tool that includes an ultrasonic transmitter and at least one ultrasonic receiver in a pitch-catch mode;
imaging the borehole at the plurality of locations using a microresistivity borehole scanner tool that includes an array of electrodes;
processing signals from the array of electrodes to generate an image of the borehole at the plurality of locations in the borehole;
determining at each of the plurality of locations in the borehole whether at least two events are represented in the pseudo-Rayleigh wave waveforms; and
if at least two events are not represented for a particular location of the plurality of locations, using the microresistivity image to identify whether the particular location presents a sharp contrast in resistivity relative to adjacent locations.

17. The method of claim 16 , further comprising:
if a sharp contrast in resistivity is present, identifying the particular location as a

Assignees

• Schlumberger Technology Corp

Inventors

• Zeroug Smaine

Classifications

• G01N29/06

  Visualisation of the interior, e.g. acoustic microscopy {(medical or veterinary diagnosis using sonic waves A61B8/00; representation of acoustic wave distribution G01H3/125, G01H9/002; short-range imaging systems using reflection of acoustic waves G01S15/8906)} · CPC title

• G01N29/46

  by spectral analysis, e.g. Fourier analysis {or wavelet analysis (spectral signal processing per se G06F17/14)} · CPC title

• G01N2291/103

  one emitter, two or more receivers · CPC title

• G01N29/041 Primary

  on the surface of the material, e.g. using Lamb, Rayleigh or shear waves · CPC title

• G01N2291/0231

  Composite or layered materials · CPC title