Method And System For Obtaining Geochemistry Information From Pyrolysis Induced By Laser Induced Breakdown Spectroscopy

• US 20160054284A1
• Filed: 08/17/2015
• Published: 02/25/2016
• Est. Priority Date: 08/19/2014
• Status: Active Grant

• Current Assignee: Halliburton Energy Services Incorporated (Halliburton Company)
• Original Assignee: InGrain, Inc. (Halliburton Company)
• Inventors: Washburn, Kathryn Elizabeth
• Granted Patent: US 10,054,577 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01J 3/0218 using optical fibers
• CPC Class Codes: G01J 3/28 Investigating the spectrum using colour filters G01J3/51
• CPC Class Codes: G01J 3/443 Emission spectrometry
• CPC Class Codes: G01N 21/718 Laser microanalysis, i.e. with formation of sample plasma
• CPC Class Codes: G01N 2201/06113 Coherent sources; lasers
• CPC Class Codes: G01N 33/241 for hydrocarbon content drilling mud G01N33/2823; drilling per se E21B; prospecting G01V

Abstract

A method for determining geochemistry of at least one geological sample with laser-induced breakdown spectral measurements performed on the geological sample in a time variant manner with spectral acquisitions made after each of a plurality of measurement shots, spectral pre-processing performed as necessary, and subsequent analysis is applied to the collected data to determine at least one geochemistry parameter of the sample. The method can provide a rapid method to estimate thermal maturity of a sample, which does not require sample preparation, and which can be non-destructive with respect to portions of the sample. A system for performing the method also is provided.

Claims

1. A method for analysing a geological sample, comprising:

subjecting at least one location of a geological sample to a plurality of successive measurement shots of laser light with each measurement shot at least partly vaporising and turning a portion of said sample into plasma to cause spectral emission;

detecting said spectral emission after each said measurement shot with at least one spectrum detector;

optional or as needed preprocessing of collected data from the spectrum detector to make it into a suitable form for analysis; and

determining at least one geochemistry parameter using the raw or pre-processed data from the spectrum detector.

2. The method of claim 1, further comprising subjecting the at least one location of a geological sample to at least one cleaning shot of laser light before the subjecting of the at least one location of a geological sample to the plurality of successive measurement shots.

3. The method of claim 1, wherein the pre-processing comprises integration of one or more peak areas to produce an intensity curve or curves, selection of the maxima of a peak for successive shots to produce an intensity curve, the actual peak spectra for successive measurement shots, or sub-regions of the spectra or the whole spectra for the successive measurement shots. Pre-processing may include two or more of the mentioned steps.

4. The method of claim 1, wherein the preprocessing comprises filtering, application of a function (e.g. taking a derivative), pre-treatment by applying an exponential fitting, bi-exponential fitting, multiple-exponential fitting, an inverse Laplace transform, a Gaussian decay fitting, compiling the data from the successive laser shots into a matrix, single vector, or other combined form. Pre-processing may include two or more of the mentioned steps.

5. The method of claim 1, wherein the geochemistry parameter is obtained wherein manual or uni or multivariate analysis or cluster analysis or self-organizing maps or neural nets or metaheuristic procedures (e.g. particle swarm optimization, genetic algorithms, etc.) is used to correlate the collected data, raw or pre-processed to determine values for at least one elemental ratio, trace elemental content of the organic matter, hydrogen index, oxygen index, programmed pyrolysis, thermal maturity property (e.g., thermal maturity, kinetic analysis), kerogen and bitumen content/discrimination, kerogen type, hydrocarbon content, hydrocarbon type, or any combinations thereof.

6. The method of claim 1, wherein the geochemistry parameter is obtained wherein manual or uni or multivariate analysis or cluster analysis or self-organising maps or neural nets or metaheuristic procedures (e.g. particle swarm optimization, genetic algorithms, etc.) is used to correlate the collected data, raw or pre-processed, to determine values for H/C ratio, H/O ratio, trace elemental content of the organic matter for at least one of S and N or other minor element in the organic matter, hydrogen index, oxygen index, programmed pyrolysis, thermal maturity property (e.g., thermal maturity, kinetic analysis), kerogen and bitumen content/discrimination, kerogen type, hydrocarbon content, hydrocarbon type, or any combinations thereof.

7. The method of claim 1, wherein said further subjecting comprises controlling operation of the laser and a plurality of said spectrum detectors to simultaneously detect spectral emissions from the geological sample across a plurality of different spectral regions, and said analysing comprises determining the presence and amount of a plurality of different elements in the geological sample.

8. The method of claim 1, wherein the sample is a rock sample.

9. The method of claim 1, wherein each of the spectrum detectors comprises a spectrometer having a CCD detector associated therewith.

10. The method of claim 1, further comprising:

(a) obtaining spatial information on the at least one sample; and

(b) determining spatially resolved geochemical information for the at least one sample using the geochemistry parameter and the spatial information.

11. A system to perform the method of claim 1.

12. A method for analysing a geological sample, comprising:

subjecting at least one location of a geological sample to a plurality of successive measurement shots of laser light with each measurement shot at least partly vaporising and turning a portion of said sample into plasma to cause spectral emission;

detecting said spectral emission after each said measurement shot with at least one spectral detector;

optional or as needed preprocessing of collected spectral data from the spectrum detector to make it into a suitable form for analysis; and

determining a reaction rate constant k for the Arrhenius equation of the at least one sample using the raw or pre-processed data from the spectrum detector.

13. The method of claim 12, wherein the determining of the reaction rate constant k using the raw or pre-processed spectral data from the spectral detector comprises at least one of:

i) determining changes in amounts of elements associated with organic matter and hydrocarbons for a portion of at least one sample that is heated by the laser-induced pyrolysis,

ii) analysing hydrocarbon species produced by pyrolysis of a portion of at least one sample from LIBS further by a flame ion detector or gas chromatography-mass spectrometry or by monitoring the weight of the sample during LIBS,

iii) monitoring the temperature of at least one sample and determining the amount of energy inputted into the portion of the sample by the laser during LIBS.

14. The method of claim 12, wherein a prefactor in the Arrhenius equation is inputted based on a priori knowledge or solved for based on measurements performed on two or more different heating rates of the sample.

15. The method of claim 14, wherein the different heating rates are obtained by one or more of different laser power, laser spot size or laser shot rate, or any combination thereof.

16. The method of claim 12, wherein the kinetic analysis is used to either solve for the activation energy distribution in the sample or the reaction rates given a known input of energy.