Material evaluation using nuclear logging tool

Patent metadata

Field	Value
Publication number	US-10677040-B2
Application number	US-201515757613-A
Country	US
Kind code	B2
Filing date	Nov 19, 2015
Priority date	Nov 19, 2015
Publication date	Jun 9, 2020
Grant date	Jun 9, 2020

Abstract

A method for material evaluation may include detecting photons from gamma ray interactions with material in an annular region between a geological formation and a casing. An energy spectrum is generated from the detected photons. A difference between materials may then be detected based on a comparison of the generated energy spectrum with a reference spectrum for a known material (e.g., good cement, known fluid).

First claim

What is claimed is:

1. A method comprising:
generating an energy spectrum from photons detected from gamma ray interactions with material in an annular region between a geological formation and a casing;
comparing the energy spectrum with at least a first reference spectrum of a plurality of reference spectra based, at least in part, on at least one of slope change, correlation coefficients, and amplitude for spectrum shapes of the energy spectrum and the first reference spectrum, wherein each of the plurality of reference spectra corresponds to a known material; and
based on the comparing, determining whether at least one of a void, gap, and fluid exists in cement in the annular region.

2. The method of claim 1 , further comprising transmitting high energy photons into the annular region.

3. The method of claim 1 , further comprising transmitting neutrons into the geological formation.

4. The method of claim 1 , wherein the photons detected from gamma ray interactions comprise photons detected on a gamma detector through a collimator.

5. The method of claim 1 , further comprising digitizing count rates of the photons detected from gamma ray interactions prior to generating the energy spectrum.

6. The method of claim 1 , further comprising substantially continuously generating an energy spectrum from photons detected from gamma ray interactions and determining whether at least one of a void, gap, and fluid exists in cement as a logging tool is moved through a cased wellbore.

7. The method of claim 1 , wherein the gamma ray interactions correspond to gamma rays emitted from a radioactive source in a logging tool.

8. The method of claim 1 , wherein detecting the photons comprises detecting scattered photons from the material in the annular region.

9. The method of claim 1 , wherein the known material comprises at least one of intact cement, cement with at least one of a void and gap, drilling fluid, and water.

10. A logging tool comprising:
a gamma detector; and
a controller coupled to the gamma detector programmed to,
generate an energy spectrum based on photon count rates which are based, at least in part, on photon interactions detected by the gamma detector;
compare the energy spectrum to reference spectra based, at least in part, on at least one of slope change, correlation coefficients, and amplitude for spectrum shapes of the energy spectrum and the reference spectra, wherein each of the reference spectra corresponds to a known material; and
based on the comparison, determine whether at least one of a void, gap, and fluid exists in a material disposed in an annular region between a geological formation and a casing.

11. The logging tool of claim 10 , further comprising a radioactive source in the logging tool a predetermined distance from the gamma detector, wherein the radioactive source generates a photon stream into the annular region.

12. The logging tool of claim 11 , wherein the radioactive source is a chemical gamma source.

13. The logging tool of claim 10 , further comprising a collimator coupled to the gamma detector.

14. The logging tool of claim 13 , wherein the collimator is angled towards a radioactive source in the logging tool, and wherein the gamma detector and collimator detect scattered photons from the material disposed in the annular region.

15. The logging tool of claim 13 , wherein the collimator is angled towards the geological formation, and wherein the gamma detector and collimator detect photons from the geological formation.

16. The logging tool of claim 10 , further comprising a neutron source in the logging tool a predetermined distance from the gamma detector, wherein the neutron source generates a neutron stream into the geological formation.

17. A system comprising:
a logging tool comprising,
a gamma detector; and
a controller coupled to the gamma detector to,
generate an energy spectrum based on photon count rates which are based, at least in part, on photon interactions detected by the gamma detector;
compare the energy spectrum to at least a first reference spectrum of a plurality of reference spectra based, at least in part, on at least one of slope change, correlation coefficients, and amplitude for spectrum shapes of the energy spectrum and the first reference spectrum, wherein each of the plurality of reference spectra corresponds to a known material; and
based on the comparison, determine whether at least one of a void, gap and fluid exists in a material disposed in an annular region between a geological formation and a casing.

18. The system of claim 17 , wherein the logging tool is a passive tool having a collimator coupled to the gamma detector, wherein the collimator is angled towards the geological formation.

19. The system of claim 17 , wherein the logging tool is an active tool having a radioactive source, the logging tool further comprising a second gamma detector wherein the gamma detector comprises a first collimator and the second gamma detector comprises a second collimator, the first collimator angled to receive scattered photons from the geological formation and the second collimator angled to receive scattered photons from the material.

20. The system of claim 17 , wherein the known material comprises at least one of intact cement, cement with at least one of a void and gap, drilling fluid, and water.

Assignees

• Halliburton Energy Services Inc

Inventors

• Hu Yike
• Guo Weijun

Classifications

• G01V5/101 Primary

  and detecting the secondary Y-rays produced in the surrounding layers of the bore hole · CPC title

• E21B33/14

  for cementing casings into boreholes · CPC title

• G01V5/125

  and detecting the secondary gamma- or X-rays in different places along the bore hole · CPC title

• E21B47/0005 Primary

  Fixed Constructions · mapped topic

• E21B47/005 Primary

  Monitoring or checking of cementation quality or level · CPC title