- Email: [email protected]
Rapid geochemical and mineralogical characterization of shale by laser-induced breakdown spectroscopy
Accepted Manuscript Rapid geochemical and mineralogical characterization of shale by laser-induced breakdown spectroscopy Kathryn E. Washburn PII: DOI: Reference:
S0146-6380(15)00058-3 http://dx.doi.org/10.1016/j.orggeochem.2015.03.004 OG 3249
To appear in:
Organic Geochemistry
Received Date: Revised Date: Accepted Date:
11 February 2015 4 March 2015 5 March 2015
Please cite this article as: Washburn, K.E., Rapid geochemical and mineralogical characterization of shale by laserinduced breakdown spectroscopy, Organic Geochemistry (2015), doi: http://dx.doi.org/10.1016/j.orggeochem. 2015.03.004
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Rapid geochemical and mineralogical characterization of shale by laser-induced breakdown spectroscopy
Kathryn E. Washburn*
Ingrain, Inc., 3733 Westheimer Road, Houston, TX 77027, USA
*
Corresponding author at: Ingrain, Inc., 3733 Westheimer Road, Houston,
TX 77027, USA. Tel: + 1 713 993 9795 ext 1052 Email address: [email protected]
1
ABSTRACT Detailed evaluation of shale geochemistry and mineralogy is important to assess petroleum reservoir quality, predict production potential and decide lateral placement and completion methods. Standard techniques for organic geochemical and mineralogical characterization are time consuming, can involve significant sample preparation and are prone to error. A new application for assessing shale samples is presented here: laser-induced breakdown spectroscopy (LIBS). A laser is used to rapidly pyrolyze shales and the changes in sample elemental composition during pyrolysis are monitored through optical emission spectroscopy. Unlike other common shale characterization methods, no specific sample preparation is required. Multivariate analysis is applied to the LIBS spectra to predict both organic geochemistry and mineralogy. The results show good correlation to TOC, Rock-Eval parameters and eleven minerals, including clay speciation. The technique also has the potential to directly measure organic hydrogen and oxygen and could provide an alternative to the indirect methods currently used.
Keywords: Shale; LIBS; laser; pyrolysis; geochemistry; thermal maturity
2
1. Introduction In addition to porosity and permeability, information on geochemistry and mineralogy is needed for assessment of unconventional shale resources. Because time from drilling to completion in unconventional reservoirs is significantly less than that of conventional petroleum systems, rapid evaluation methods are required. However, current methods for assessing geochemistry and mineralogy are time consuming and error prone. The standard methods for geochemical characterization of source and reservoir rocks are total organic carbon (TOC) and programmed pyrolysis methods using equipment such as the Rock-Eval and the Source Rock Analyzer (Peters, 1986; Bordenave, 1993). Programmed pyrolysis methods heat in multiple stages small amounts of pulverized sample to obtain information relating to free oil and bitumen content (S1), hydrocarbon-generating potential (S2), organic oxygen content (S3) and thermal maturity (Tmax). These parameters and TOC can be used to estimate kerogen quality through calculated parameters like hydrogen index (HI), oxygen index (OI) and production index (PI). For samples with significant carbonate content, treatment with HCl acid overnight is needed to remove most carbonate minerals to prevent breakdown during pyrolysis that can lead to erroneously high TOC and S3 values. Fourier transform infrared spectroscopy (FTIR) has been used to evaluate both organic geochemistry and mineralogy of shale samples. While the measurement itself is rapid, sample preparation for transmission and
3
diffuse reflectance acquisition modes are exacting and the attenuated total reflectance method still requires samples to be crushed. FTIR characterization of shale geochemistry has shown promise but has limitations. Herron et al. (2014) were able to predict TOC for thermally immature samples, but were unable to do so for thermally mature samples. Predictions of organic geochemical properties tend rely heavily on the aliphatic regions of the spectra due to interferences from carbonates in the spectral regions occupied by aromatic carbon, making predictions on higher thermal maturity samples difficult. Washburn and Birdwell (2013) were able to predict TOC, S1, S2 and S3 even for thermally mature samples, but were still unable to obtain a satisfactory correlation with HI or OI. Also, no reliable correlation was seen with Tmax. FTIR mineralogy results on artificial mixtures show good prediction (Ballard, 2007), but the models derived from artificial mixtures produce poor results when applied to real samples (Müller et al., 2014). This paper presents the results of laser-induced breakdown spectroscopy (LIBS) as a new method for shale geochemical and mineralogical analysis. The technique has been used previously to characterize other types of geological materials (Harmon et al., 2006; Tucker et al., 2010), but not on petroleum shale reservoir and source rock samples. LIBS uses a laser to ablate a small portion of sample, typically a few nanograms, to create a high temperature plasma. As the plasma cools, it
4
emits light at characteristic elemental wavelengths whose intensities are determined by the composition of the sample. Unlike X-ray fluorescence, LIBS readily measures light elements such as hydrogen and carbon. Instead of heating the sample in an oven, as with programmed pyrolysis, the laser is used to rapidly pyrolyze the sample and the elemental changes that occur are observed through optical emission spectroscopy. The initial spectral measurement observes elements from both the organic and inorganic constituents. In addition to creating the plasma, some of the energy from the laser is transferred to the surrounding matrix and volatizes nearby organic matter. This is observed in the next spectral measurements as the loss of elements associated with organic matter, such as hydrogen and carbon. As with traditional programmed pyrolysis, lighter organic matter such as hydrocarbons and bitumen will volatize readily while kerogen requires more heating. The more thermally mature, the longer it will take the laser to volatize the kerogen. The magnitude and rate of the loss of organic associated elements can be used to characterize organic content and type. Changes in the spectra from the start to the end of pyrolysis allows the organic and inorganic matter compositions of the sample to be separated. Because dozens of elements are measured simultaneously, the method is more sensitive to sample changes compared to standard pyrolysis, which detects only carbon species. Sample measurement takes about 30 seconds. LIBS does not require any specific sample preparation such as
5
pulverization or pretreatment with acid and can be performed on a wide variety of sample types, ranging from cuttings to whole core. The lack of sample preparation and rapid measurement makes LIBS an ideal method for high throughput analysis. The technique presented here is similar to laser-induced pyrolysis (LIPS), which has been used to characterize shales (Lalanne et al., 2013) While both methods use a laser to pyrolyze the sample, LIPS, unlike LIBS, collects the volatized products and analyzes them using gas chromatography and mass spectroscopy. LIPS has been used to provide TOC information, but not other geochemical parameters nor mineralogy, making LIBS a more complete assessment of organic and inorganic geochemistry. In a different geochemistry application, LIBS has been used to evaluate coal properties such as moisture, ash, volatile matter, and calorific value (Yuan et al., 2013).
2. Experimental Measurements were made on 145 shale samples from multiple formations across several continents. Their geochemistry spans a range of TOC contents from trace to extremely rich and from thermally immature through to the dry gas window. Geochemistry was measured through a combination of LECO TOC, Rock-Eval 2 and the Source Rock Analyzer. Mineralogy was evaluated using XRD and included clay speciation. LIBS measurements were made using an Insight 3464 with a 4 channel
6
spectrometer and 50 mJ 1064 laser from TSI (Minneapolis, MN). An argon purge was performed during measurement to avoid atmospheric interference. Four hundred spectra were recorded at 10 Hz with a laser spot size of 400 μm. Spectra were then concatenated and analyzed by a partial least squares (PLS) regression in the R programming language. The PLS regression creates a model relating the rate and magnitude of change of elemental composition during pyrolysis to mineralogical and geochemical properties. Validation of the model was performed with the Leave-One-Out (LOO) method.
3. Discussion Results of the PLSR model validation between geochemistry measurements and LIBS predictions are shown in Fig. 1. An excerpt of the LIBS spectra in the region containing hydrogen from the start and end of pyrolysis are shown in Fig. 2; the loss of hydrogen can clearly be seen. PLSR validation results between XRD and LIBS predictions are shown in Fig. 3. The average absolute deviations (a.a.d), the mean error between the measured and predicted values, are shown on the individual figures. LIBS shows good prediction capability for TOC and Rock-Eval parameters. There was scatter in the higher Tmax predictions as measured Tmax values over 500 °C were more uncertain due to low, broad peaks in the pyrograms. As LIBS can predict OI and HI, these results can be plotted on a modified van Krevelen diagram to gain insights into kerogen typing and
7
thermal maturity, especially if related immature samples are available for comparison. While HI is found here by correlation to Rock-Eval parameters, this method is suboptimal. HI from programmed pyrolysis is calculated by dividing S2 by TOC. There is no direct measurement of hydrogen content and parameters derived from ratios are prone to instability and high errors, particularly if the denominator is small, due to error propagation. As LIBS can measure hydrogen, determining the percentage of hydrogen in the organic matter directly will provide a more reliable measure of kerogen quality. This is also true for the oxygen index. Similarly, while there is good correlation with Tmax, this value is simply a proxy for the true desired information: how much hydrogen is in the sample compared to immature samples of the same formation? It is anticipated that using LIBS to compare hydrogen content between immature and mature samples from shale formations will provide a better evaluation of thermal maturity. The method also shows good predictive capability for mineralogy. The deviations are similar to typical errors from techniques like XRD and FTIR (± 5 wt%). The LIBS results show good estimation of pyrite and marcasite as well as feldspar speciation. These are particularly difficult to evaluate using FTIR due to a lack of distinctive peaks for the former and highly similar spectra for the latter. It is expected that LIBS will be able to predict the presence of other minerals such as gypsum, siderite, ankerite, apatite, halite
8
and R1 and R2 mixed layer clays. However, there were not enough samples with these minerals present to be statistically significant.
4. Conclusions Results show LIBS is a rapid, quantitative technique to assess shale organic geochemistry and mineralogy with minimal sample preparation. Data show good correlation with results from standard methods and errors are within similar experimental tolerances. The technique may provide direct measurement of shale properties such as organic hydrogen and oxygen whereas other routine analyses can only provide indirect estimates.
Acknowledgements The author thanks Justin Birdwell, Steve Buckley, Markus Gaelli and Ed Terrell for helpful discussions.
References Ballard, B.D., 1997. Quantitative mineralogy of reservoir rocks using Fourier transform spectroscopy. SPE Annual Technical Conference and Exhibition, SPE-113023-STU. Bordenave, M., 1993. Applied Petroleum Geochemistry. Editions Technip, Paris. Harmon, R.S., DeLucia, F.C., McManus, C.E., McMillian, N.J., Jenkins,
9
T.F., Walsh, M.E., Miziolek, A., 2006. Laser-induced breakdown spectroscopy – An emerging chemical sensor technology for real-time, field portable, geochemical, mineralogical and environmental applications. Frontiers in Analytical Geochemistry 21, 730-747. Herron, M.M., Loan, M.E., Charsky, A.M., Herron, S.L., Pomerantz, A.E., Polyakov, M., 2014. Kerogen content and maturity, mineralogy and clay typing from drifts analysis of cuttings or core. Petrophysics 55, 435-446. Lalanne, B., Le Bihan, A., Elias, R., Poyol, E., 2013. How to cope with some of the challenges associated with laboratory measurements on gas shale core samples. European Unconventional Resources Conference and Exhibition, SPE-167709-MS. Muller, C.M., Pejcicv, B., Esteban, L., Piane, C.D., Raven, M., Mizaikoff, B., 2014. Infrared attenuated total reflectance spectroscopy: An innovative strategy for analyzing mineral components in energy relevant systems. Scientific Reports 4, 1-11. Peters, K.E., 1986. Guidelines for evaluating petroleum source rock using programmed pyrolysis. AAPG Bulletin 70, 318-329. Tucker, J.M., Dyar, M.D., Schaefer, M.W., Clegg, S.M., Wiens, R.C., 2010. Optimization of laser-induced breakdown spectroscopy for rapid geochemical analysis. Chemical Geology 277, 137-148. Washburn, K.E., Birdwell, J.E., 2013. Multivariate analysis of ATR-FTIR
10
spectra for assessment of oil shale organic geochemical properties. Organic Geochemistry 63, 1-7. Yuan, T., Wang, Z., Lui, S.L., Fu, Y., Li, Z., Liu, J, Ni, W., 2013. Coal property analysis using laser-induced breakdown spectroscopy. Journal of Analytic Atomic Spectroscopy 28, 1045-1053.
11
F gurress Fig
F g. 1. Fig 1 G Geooch hem mistry y pa ara ameeteers meeassured using g LEC L CO TO OC an nd p ogrram pro mmed py yrollysiis vs. v geeoch hem misstry y pred p dicttion ns froom LIIBS S.
12
Fig. 2. Excerpted wavelengths of LIBS spectra from the start (dotted) and end (solid) of pyrolysis. Selected elemental peaks have been labeled.
13
Fig g. 3. Min nerraloogy y frrom m XRD D (w wt% %) vs.. mineera alog gy preedictioonss frrom m LIB BS.
1 14
S0146-6380(15)00058-3 http://dx.doi.org/10.1016/j.orggeochem.2015.03.004 OG 3249
To appear in:
Organic Geochemistry
Received Date: Revised Date: Accepted Date:
11 February 2015 4 March 2015 5 March 2015
Please cite this article as: Washburn, K.E., Rapid geochemical and mineralogical characterization of shale by laserinduced breakdown spectroscopy, Organic Geochemistry (2015), doi: http://dx.doi.org/10.1016/j.orggeochem. 2015.03.004
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Rapid geochemical and mineralogical characterization of shale by laser-induced breakdown spectroscopy
Kathryn E. Washburn*
Ingrain, Inc., 3733 Westheimer Road, Houston, TX 77027, USA
*
Corresponding author at: Ingrain, Inc., 3733 Westheimer Road, Houston,
TX 77027, USA. Tel: + 1 713 993 9795 ext 1052 Email address: [email protected]
1
ABSTRACT Detailed evaluation of shale geochemistry and mineralogy is important to assess petroleum reservoir quality, predict production potential and decide lateral placement and completion methods. Standard techniques for organic geochemical and mineralogical characterization are time consuming, can involve significant sample preparation and are prone to error. A new application for assessing shale samples is presented here: laser-induced breakdown spectroscopy (LIBS). A laser is used to rapidly pyrolyze shales and the changes in sample elemental composition during pyrolysis are monitored through optical emission spectroscopy. Unlike other common shale characterization methods, no specific sample preparation is required. Multivariate analysis is applied to the LIBS spectra to predict both organic geochemistry and mineralogy. The results show good correlation to TOC, Rock-Eval parameters and eleven minerals, including clay speciation. The technique also has the potential to directly measure organic hydrogen and oxygen and could provide an alternative to the indirect methods currently used.
Keywords: Shale; LIBS; laser; pyrolysis; geochemistry; thermal maturity
2
1. Introduction In addition to porosity and permeability, information on geochemistry and mineralogy is needed for assessment of unconventional shale resources. Because time from drilling to completion in unconventional reservoirs is significantly less than that of conventional petroleum systems, rapid evaluation methods are required. However, current methods for assessing geochemistry and mineralogy are time consuming and error prone. The standard methods for geochemical characterization of source and reservoir rocks are total organic carbon (TOC) and programmed pyrolysis methods using equipment such as the Rock-Eval and the Source Rock Analyzer (Peters, 1986; Bordenave, 1993). Programmed pyrolysis methods heat in multiple stages small amounts of pulverized sample to obtain information relating to free oil and bitumen content (S1), hydrocarbon-generating potential (S2), organic oxygen content (S3) and thermal maturity (Tmax). These parameters and TOC can be used to estimate kerogen quality through calculated parameters like hydrogen index (HI), oxygen index (OI) and production index (PI). For samples with significant carbonate content, treatment with HCl acid overnight is needed to remove most carbonate minerals to prevent breakdown during pyrolysis that can lead to erroneously high TOC and S3 values. Fourier transform infrared spectroscopy (FTIR) has been used to evaluate both organic geochemistry and mineralogy of shale samples. While the measurement itself is rapid, sample preparation for transmission and
3
diffuse reflectance acquisition modes are exacting and the attenuated total reflectance method still requires samples to be crushed. FTIR characterization of shale geochemistry has shown promise but has limitations. Herron et al. (2014) were able to predict TOC for thermally immature samples, but were unable to do so for thermally mature samples. Predictions of organic geochemical properties tend rely heavily on the aliphatic regions of the spectra due to interferences from carbonates in the spectral regions occupied by aromatic carbon, making predictions on higher thermal maturity samples difficult. Washburn and Birdwell (2013) were able to predict TOC, S1, S2 and S3 even for thermally mature samples, but were still unable to obtain a satisfactory correlation with HI or OI. Also, no reliable correlation was seen with Tmax. FTIR mineralogy results on artificial mixtures show good prediction (Ballard, 2007), but the models derived from artificial mixtures produce poor results when applied to real samples (Müller et al., 2014). This paper presents the results of laser-induced breakdown spectroscopy (LIBS) as a new method for shale geochemical and mineralogical analysis. The technique has been used previously to characterize other types of geological materials (Harmon et al., 2006; Tucker et al., 2010), but not on petroleum shale reservoir and source rock samples. LIBS uses a laser to ablate a small portion of sample, typically a few nanograms, to create a high temperature plasma. As the plasma cools, it
4
emits light at characteristic elemental wavelengths whose intensities are determined by the composition of the sample. Unlike X-ray fluorescence, LIBS readily measures light elements such as hydrogen and carbon. Instead of heating the sample in an oven, as with programmed pyrolysis, the laser is used to rapidly pyrolyze the sample and the elemental changes that occur are observed through optical emission spectroscopy. The initial spectral measurement observes elements from both the organic and inorganic constituents. In addition to creating the plasma, some of the energy from the laser is transferred to the surrounding matrix and volatizes nearby organic matter. This is observed in the next spectral measurements as the loss of elements associated with organic matter, such as hydrogen and carbon. As with traditional programmed pyrolysis, lighter organic matter such as hydrocarbons and bitumen will volatize readily while kerogen requires more heating. The more thermally mature, the longer it will take the laser to volatize the kerogen. The magnitude and rate of the loss of organic associated elements can be used to characterize organic content and type. Changes in the spectra from the start to the end of pyrolysis allows the organic and inorganic matter compositions of the sample to be separated. Because dozens of elements are measured simultaneously, the method is more sensitive to sample changes compared to standard pyrolysis, which detects only carbon species. Sample measurement takes about 30 seconds. LIBS does not require any specific sample preparation such as
5
pulverization or pretreatment with acid and can be performed on a wide variety of sample types, ranging from cuttings to whole core. The lack of sample preparation and rapid measurement makes LIBS an ideal method for high throughput analysis. The technique presented here is similar to laser-induced pyrolysis (LIPS), which has been used to characterize shales (Lalanne et al., 2013) While both methods use a laser to pyrolyze the sample, LIPS, unlike LIBS, collects the volatized products and analyzes them using gas chromatography and mass spectroscopy. LIPS has been used to provide TOC information, but not other geochemical parameters nor mineralogy, making LIBS a more complete assessment of organic and inorganic geochemistry. In a different geochemistry application, LIBS has been used to evaluate coal properties such as moisture, ash, volatile matter, and calorific value (Yuan et al., 2013).
2. Experimental Measurements were made on 145 shale samples from multiple formations across several continents. Their geochemistry spans a range of TOC contents from trace to extremely rich and from thermally immature through to the dry gas window. Geochemistry was measured through a combination of LECO TOC, Rock-Eval 2 and the Source Rock Analyzer. Mineralogy was evaluated using XRD and included clay speciation. LIBS measurements were made using an Insight 3464 with a 4 channel
6
spectrometer and 50 mJ 1064 laser from TSI (Minneapolis, MN). An argon purge was performed during measurement to avoid atmospheric interference. Four hundred spectra were recorded at 10 Hz with a laser spot size of 400 μm. Spectra were then concatenated and analyzed by a partial least squares (PLS) regression in the R programming language. The PLS regression creates a model relating the rate and magnitude of change of elemental composition during pyrolysis to mineralogical and geochemical properties. Validation of the model was performed with the Leave-One-Out (LOO) method.
3. Discussion Results of the PLSR model validation between geochemistry measurements and LIBS predictions are shown in Fig. 1. An excerpt of the LIBS spectra in the region containing hydrogen from the start and end of pyrolysis are shown in Fig. 2; the loss of hydrogen can clearly be seen. PLSR validation results between XRD and LIBS predictions are shown in Fig. 3. The average absolute deviations (a.a.d), the mean error between the measured and predicted values, are shown on the individual figures. LIBS shows good prediction capability for TOC and Rock-Eval parameters. There was scatter in the higher Tmax predictions as measured Tmax values over 500 °C were more uncertain due to low, broad peaks in the pyrograms. As LIBS can predict OI and HI, these results can be plotted on a modified van Krevelen diagram to gain insights into kerogen typing and
7
thermal maturity, especially if related immature samples are available for comparison. While HI is found here by correlation to Rock-Eval parameters, this method is suboptimal. HI from programmed pyrolysis is calculated by dividing S2 by TOC. There is no direct measurement of hydrogen content and parameters derived from ratios are prone to instability and high errors, particularly if the denominator is small, due to error propagation. As LIBS can measure hydrogen, determining the percentage of hydrogen in the organic matter directly will provide a more reliable measure of kerogen quality. This is also true for the oxygen index. Similarly, while there is good correlation with Tmax, this value is simply a proxy for the true desired information: how much hydrogen is in the sample compared to immature samples of the same formation? It is anticipated that using LIBS to compare hydrogen content between immature and mature samples from shale formations will provide a better evaluation of thermal maturity. The method also shows good predictive capability for mineralogy. The deviations are similar to typical errors from techniques like XRD and FTIR (± 5 wt%). The LIBS results show good estimation of pyrite and marcasite as well as feldspar speciation. These are particularly difficult to evaluate using FTIR due to a lack of distinctive peaks for the former and highly similar spectra for the latter. It is expected that LIBS will be able to predict the presence of other minerals such as gypsum, siderite, ankerite, apatite, halite
8
and R1 and R2 mixed layer clays. However, there were not enough samples with these minerals present to be statistically significant.
4. Conclusions Results show LIBS is a rapid, quantitative technique to assess shale organic geochemistry and mineralogy with minimal sample preparation. Data show good correlation with results from standard methods and errors are within similar experimental tolerances. The technique may provide direct measurement of shale properties such as organic hydrogen and oxygen whereas other routine analyses can only provide indirect estimates.
Acknowledgements The author thanks Justin Birdwell, Steve Buckley, Markus Gaelli and Ed Terrell for helpful discussions.
References Ballard, B.D., 1997. Quantitative mineralogy of reservoir rocks using Fourier transform spectroscopy. SPE Annual Technical Conference and Exhibition, SPE-113023-STU. Bordenave, M., 1993. Applied Petroleum Geochemistry. Editions Technip, Paris. Harmon, R.S., DeLucia, F.C., McManus, C.E., McMillian, N.J., Jenkins,
9
T.F., Walsh, M.E., Miziolek, A., 2006. Laser-induced breakdown spectroscopy – An emerging chemical sensor technology for real-time, field portable, geochemical, mineralogical and environmental applications. Frontiers in Analytical Geochemistry 21, 730-747. Herron, M.M., Loan, M.E., Charsky, A.M., Herron, S.L., Pomerantz, A.E., Polyakov, M., 2014. Kerogen content and maturity, mineralogy and clay typing from drifts analysis of cuttings or core. Petrophysics 55, 435-446. Lalanne, B., Le Bihan, A., Elias, R., Poyol, E., 2013. How to cope with some of the challenges associated with laboratory measurements on gas shale core samples. European Unconventional Resources Conference and Exhibition, SPE-167709-MS. Muller, C.M., Pejcicv, B., Esteban, L., Piane, C.D., Raven, M., Mizaikoff, B., 2014. Infrared attenuated total reflectance spectroscopy: An innovative strategy for analyzing mineral components in energy relevant systems. Scientific Reports 4, 1-11. Peters, K.E., 1986. Guidelines for evaluating petroleum source rock using programmed pyrolysis. AAPG Bulletin 70, 318-329. Tucker, J.M., Dyar, M.D., Schaefer, M.W., Clegg, S.M., Wiens, R.C., 2010. Optimization of laser-induced breakdown spectroscopy for rapid geochemical analysis. Chemical Geology 277, 137-148. Washburn, K.E., Birdwell, J.E., 2013. Multivariate analysis of ATR-FTIR
10
spectra for assessment of oil shale organic geochemical properties. Organic Geochemistry 63, 1-7. Yuan, T., Wang, Z., Lui, S.L., Fu, Y., Li, Z., Liu, J, Ni, W., 2013. Coal property analysis using laser-induced breakdown spectroscopy. Journal of Analytic Atomic Spectroscopy 28, 1045-1053.
11
F gurress Fig
F g. 1. Fig 1 G Geooch hem mistry y pa ara ameeteers meeassured using g LEC L CO TO OC an nd p ogrram pro mmed py yrollysiis vs. v geeoch hem misstry y pred p dicttion ns froom LIIBS S.
12
Fig. 2. Excerpted wavelengths of LIBS spectra from the start (dotted) and end (solid) of pyrolysis. Selected elemental peaks have been labeled.
13
Fig g. 3. Min nerraloogy y frrom m XRD D (w wt% %) vs.. mineera alog gy preedictioonss frrom m LIB BS.
1 14