Thermal analysis for source rocks

Patent metadata

Field	Value
Publication number	US-11268919-B2
Application number	US-201916569474-A
Country	US
Kind code	B2
Filing date	Sep 12, 2019
Priority date	Sep 12, 2019
Publication date	Mar 8, 2022
Grant date	Mar 8, 2022

Abstract

A system and method for evaluating a geological formation including subjecting a source-rock sample from the geological formation to atomic force microscopy (AFM) to determine a thermal property or material property of the source-rock sample. The properties determined may include thermal conductivity or material transition temperature.

First claim

What is claimed is:

1. A method of evaluating a geological formation, comprising:
preparing a source-rock sample from the geological formation;
acquiring a topography map of a region of the source-rock sample at a resolution less than 1 micrometer (μm);
choosing the region as a region of interest identified based on a reflected-light optical image of the source-rock sample;
selecting measurement areas of the region based on the topography map; and
determining, via atomic force microscopy (AFM), a thermal conductivity of the source-rock sample at the measurement areas at a scale less than 1 millimeter.

2. The method of claim 1 , wherein the measurement areas each comprise a width in a range of 10 μm to 500 μm and a length in a range of 10 μm to 500 μm.

3. The method of claim 1 , wherein choosing the region as a region of interest identified based on a reflected-light optical image comprises evaluating gray scale, color variation, domain shape, or features adjacent the region, or any combinations thereof.

4. The method of claim 1 , comprising selecting the region as a region of interest identified based on an analysis of the source-rock sample, the analysis comprising scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), fluorescence, AFM-infrared red (IR), or Fourier-transform infrared spectroscopy (FTIR), or any combinations thereof.

5. The method of claim 1 , comprising identifying a portion of interest of the region based on the topography map, wherein the selecting comprises selecting measurement areas of the region based on the portion of interest and on the topography map, and wherein the portion of interest comprises organic domains or inorganic domains, or both, of a rock structure of the source-rock sample.

6. The method of claim 1 , wherein the AFM comprises scanning thermal microscopy (SThM).

7. The method of claim 1 , wherein determining the thermal conductivity via AFM comprises determining the thermal conductivity with an AFM instrument in a scanning thermal microscopy (SThM) mode.

8. The method of claim 1 , wherein determining the thermal conductivity via AFM comprises applying a voltage to a cantilever tip portion of a cantilever of an AFM instrument utilized to determine the thermal conductivity.

9. The method of claim 8 , comprising maintaining the cantilever tip portion at a set-point temperature, wherein determining the thermal conductivity comprises transferring heat from the cantilever tip portion to the source-rock sample.

10. The method of claim 8 , wherein determining the thermal conductivity comprises heating the source-rock sample and transferring heat from the source-rock sample to the cantilever tip portion.

11. The method of claim 8 , wherein determining the thermal conductivity comprises measuring a diameter of the cantilever tip portion, wherein the diameter is in a range of 10 nm to 100 nm.

12. The method of claim 8 , wherein applying voltage to the cantilever tip portion comprises applying the voltage to a heating element on the cantilever tip portion.

13. The method of claim 12 , wherein the heating element comprises a circuit printed on the cantilever.

14. The method of claim 13 , wherein determining the thermal conductivity comprises measuring a voltage difference across the circuit printed on the cantilever.

15. A method of evaluating a geological formation, comprising:
preparing a source-rock sample from the geological formation;
acquiring a topography map of a region of the source-rock sample at a resolution less than 1 micrometer (μm);
selecting measurement areas of the region based on the topography map;
generating a calibration curve based on standards samples each having a known thermal conductivity; and
determining, via atomic force microscopy (AFM), a thermal conductivity of the source-rock sample at the measurement areas at a scale less than 1 millimeter, wherein determining via AFM the thermal conductivity of the source-rock sample comprises utilizing the calibration curve.

16. The method of claim 15 , wherein the calibration curve relates a voltage difference across a heating element of a cantilever tip portion of an AFM instrument with values of the thermal conductivity.

17. The method of claim 16 , wherein the heating element comprises a circuit printed on the cantilever tip portion, and wherein determining via AFM the thermal conductivity of the source-rock sample comprises measuring a voltage difference across the circuit printed on the cantilever tip portion while the cantilever tip portion is interacting with the source-rock sample.

18. The method of claim 17 , wherein determining via AFM the thermal conductivity of the source-rock sample comprises correlating the measured voltage difference with a value of a thermal conductivity indicated by the calibration curve.

19. The method of claim 17 , wherein measuring the voltage difference comprises measuring a change in the voltage difference.

20. The method of claim 19 , wherein generating the calibration curve comprises measuring the voltage difference across the heating element with the cantilever tip portion interacting with the standards samples.

21. A method of evaluating a geological formation, comprising:
mounting a source-rock sample from the geological formation to a sample holder of an atomic force microscopy (AFM) instrument;
identifying a region of interest of the source-rock sample; and
determining a thermal conductivity of the region via the AFM instrument in a scanning thermal microscopy (SThM) mode, wherein the AFM instrument comprises a cantilever tip, and wherein determining the thermal conductivity comprises checking a diameter or a width of the cantilever tip.

22. The method of claim 21 , wherein identifying the region of interest is based on an analysis of the source-rock sample, the analysis being via a reflected-light optical image, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), fluorescence, AFM-infrared red (IR), or Fourier-transform infrared spectroscopy (FTIR), or any combinations thereof.

23. The method of claim 21 , comprising determining an indication of heat flow from the cantilever tip to a known material standard.

24. The method of claim 21 , comprising determining an indication of heat flow from the cantilever tip to an environment of the AFM instrument at least 1 millimeter (mm) from the mounted source-rock sample.

25. The method of claim 21 , wherein mounting the source-rock sample comprises mounting the source-rock sample with a specified orientation relative to a bedding of the source-rock sample.

26. The method of claim 21 , wherein determining the thermal conductivity comprises transferring heat from the cantilever tip to the source-rock sample mounted in the sample holder.

27. The method of claim 21 , comprising maintaining the cantilever tip at a constant temperature.

28. The method of claim 27 , wherein the constant temperature comprises a room temperature.

29. The method of claim 27 , comprising setting temperature and ramp parameters of a heating stage of the AFM instrument to heat the source-rock sample, the heating stage providing a heating ramp during the determining of the thermal conductivity.

30. The method of claim 29 , comprising collecting SThM data and topography for the region at a resolution less than 1 millim

Assignees

• Saudi Arabian Oil Co

Inventors

• Eichmann Shannon L
• Hull Katherine Leigh
• Abousleiman Younane N
• Jacobi David

Classifications

• G01Q60/58 Primary

  SThM [Scanning Thermal Microscopy] or apparatus therefor, e.g. SThM probes · CPC title

• G01Q60/24

  AFM [Atomic Force Microscopy] or apparatus therefor, e.g. AFM probes · CPC title

• G01N33/241

  for hydrocarbon content · CPC title

• G01N25/18 Primary

  by investigating thermal conductivity (by calorimetry G01N25/20; by measuring change of resistance of an electrically-heated body G01N27/18) · CPC title