To test reproducibility of vitrinite and solid bitumen reflectance measurements in mudrocks, an interlaboratory study (ILS) was conducted using six samples from United States unconventional petroleum systems. Samples selected from the Marcellus, Haynesville, Eagle Ford, Barnett, Bakken and Woodford are representative of resource plays currently under exploitation in North America. All samples are from marine depositional environments, are thermally mature (Tmax >445°C) and have moderate to high organic matter content (2.9 to 11.6 wt.% TOC). The organic matter of the sample is dominated by solid bitumen, which contains intraparticle nano-porosity. Visual evaluation of organic nano-porosity via SEM suggests that intraparticle organic nanopores are most abundant in dry gas maturity samples and less abundant at lower wet gas/condensate and peak oil maturities. Samples were distributed to ILS participants in forty laboratories in the Americas, Europe, Africa and Australia; thirty- seven independent sets of results were received. Mean vitrinite reflectance (VRo) values from ILS participants range from 0.90 to 1.83% whereas mean solid bitumen reflectance (BRo) values range from 0.85 to 2.04% (no outlying values excluded), confirming the thermally mature nature of all six samples. Using multiple statistical approaches to eliminate outlying values, we evaluated reproducibility limit R, the maximum difference between valid mean reflectance results obtained on the same sample by different operators in different laboratories using different instruments. Removal of outlying values where the individual signed multiple of standard deviation was >1.0 produced lowest R values, generally ≤0.5% (absolute reflectance), similar to a prior ILS for similar samples. Other traditional approaches to outlier removal (outside mean ± 1.5*interquartile range and outside F10 to F90 percentile range) also produced similar R values. Standard deviation values <0.15*(VRo or BRo) reduce R and should be a requirement of dispersed organic matter reflectance analysis. R values were 0.1% to 0.2% for peak oil thermal maturity, about 0.3% for wet gas/condensate maturity and 0.4% to 0.5% for dry gas maturity. That is, these R values represent the uncertainty (in absolute reflectance) that users of vitrinite and solid bitumen reflectance data should assign to any one individual reported mean reflectance value from a similar thermal maturity mudrock sample. R values of this magnitude indicate a need for further standardization of reflectance measurement of dispersed organic matter. Furthermore, these R values quantify realistic interlaboratory measurement dispersion for a difficult but critically important analytical technique necessary for thermal maturity determination in unconventional petroleum systems.

To test reproducibility of vitrinite and solid bitumen reflectance measurements in mudrocks, an interlaboratory study (ILS) was conducted using six samples from United States unconventional petroleum systems. Samples selected from the Marcellus, Haynesville, Eagle Ford, Barnett, Bakken and Woodford are representative of resource plays currently under exploitation in North America. All samples are from marine depositional environments, are thermally mature (Tmax >445°C) and have moderate to high organic matter content (2.9 to 11.6 wt.% TOC). The organic matter of the sample is dominated by solid bitumen, which contains intraparticle nano-porosity. Visual evaluation of organic nano-porosity via SEM suggests that intraparticle organic nanopores are most abundant in dry gas maturity samples and less abundant at lower wet gas/condensate and peak oil maturities. Samples were distributed to ILS participants in forty laboratories in the Americas, Europe, Africa and Australia; thirty- seven independent sets of results were received. Mean vitrinite reflectance (VRo) values from ILS participants range from 0.90 to 1.83% whereas mean solid bitumen reflectance (BRo) values range from 0.85 to 2.04% (no outlying values excluded), confirming the thermally mature nature of all six samples. Using multiple statistical approaches to eliminate outlying values, we evaluated reproducibility limit R, the maximum difference between valid mean reflectance results obtained on the same sample by different operators in different laboratories using different instruments. Removal of outlying values where the individual signed multiple of standard deviation was >1.0 produced lowest R values, generally ≤0.5% (absolute reflectance), similar to a prior ILS for similar samples. Other traditional approaches to outlier removal (outside mean ± 1.5*interquartile range and outside F10 to F90 percentile range) also produced similar R values. Standard deviation values <0.15*(VRo or BRo) reduce R and should be a requirement of dispersed organic matter reflectance analysis. R values were 0.1% to 0.2% for peak oil thermal maturity, about 0.3% for wet gas/condensate maturity and 0.4% to 0.5% for dry gas maturity. That is, these R values represent the uncertainty (in absolute reflectance) that users of vitrinite and solid bitumen reflectance data should assign to any one individual reported mean reflectance value from a similar thermal maturity mudrock sample. R values of this magnitude indicate a need for further standardization of reflectance measurement of dispersed organic matter. Furthermore, these R values quantify realistic interlaboratory measurement dispersion for a difficult but critically important analytical technique necessary for thermal maturity determination in unconventional petroleum systems.

Thirty-two organic-rich samples from the lower and upper shale members of the Devonian–Mississippian Bakken Formation were collected from eight cores across the Williston Basin, USA, at depths (~7,575–11,330 ft) representing immature through post peak oil/early condensate thermal maturity conditions. Reflectance results were correlated to programmed temperature pyrolysis parameters [hydrogen index (HI), production index (PI), Tmax], normal hydrocarbon and isoprenoid analysis of extractable organic matter (pristane/n-C17, phytane/n-C18) from GC analysis, and peak ratios from FTIR spectroscopy (branching ratio, A-factor).

Thirty-two organic-rich samples from the lower and upper shale members of the Devonian–Mississippian Bakken Formation were collected from eight cores across the Williston Basin, USA, at depths (~7,575–11,330 ft) representing immature through post peak oil/early condensate thermal maturity conditions. Reflectance results were correlated to programmed temperature pyrolysis parameters [hydrogen index (HI), production index (PI), Tmax], normal hydrocarbon and isoprenoid analysis of extractable organic matter (pristane/n-C17, phytane/n-C18) from GC analysis, and peak ratios from FTIR spectroscopy (branching ratio, A-factor).

Geological models for petroleum generation suggest thermal conversion of oil-prone sedimentary organic matter in the presence of water promotes increased liquid saturate yield, whereas absence of water causes formation of an aromatic, cross-linked solid bitumen residue. To test the influence of exchangeable hydrogen from water, organic-rich (22 wt.% total organic carbon, TOC) mudrock samples from the Eocene lacustrine Green River Mahogany zone oil shale were pyrolyzed under hydrous and anhydrous conditions at temperatures between 300 and 370°C for 72 hrs. Petrographic approaches including optical microscopy, reflectance, Raman spectroscopy, and scanning electron and transmission electron microscopy, supplemented by geochemical screening measurements (TOC content and programmed pyrolysis), were used to quantify differences in relative appearance, abundance and composition of solid bitumen newly generated during the pyrolysis experiments. Results show hydrous residues contain lower TOC, comprised of solid bitumen with higher aromaticity, and textures indicative of lower viscosities, than anhydrous residues from the same temperature pyrolysis conditions. These observations suggest solid bitumen forming from thermal conversion of oil-prone sedimentary organic matter under anhydrous conditions is less aromatic, although more cross-linked, than solid bitumen forming under hydrous conditions at the same time-temperature combination. A radical disproportionation mechanism favored in the presence of hydrogen radical donation from water promotes aromatization in the solid residue with concomitant expulsion of saturated hydrocarbons.

A full description of all collection and processing steps is included in this data release as: ‘SmithCreekPlayaNV_16aug2022_ProcessingSteps.pdf’. Reflectance data were collected using Malvern Panalytical ASD FieldSpec® 4 Hi-Res NG Spectroradiometers with custom VNIR gratings (hereafter referred to as ASD spectrometers) on August 16, 2022, at a field site in Smith Creek Valley, Nevada, USA. The ASD spectrometers used have a spectral range of 0.35 to 2.5 micronswith 2151 channels of data reported (Malvern Panalytical, 2018). Reflected sunlight was measured with the bare fiber (no fore optic), having a field of view of ~22 degrees, while traversing the area of the field site. Additional measurements of reflected artificial light were made at discrete sample points within the field site using an ASD Hi-Brite Contact Probe. Averages of relative reflectance spectra for the field site were computed separately from the sunlight and artificial light measurements. These averages were converted from relative reflectance to absolute reflectance by compensating for the absorption properties of the reference panel, a National Institute of Standards and Technology traceable Labsphere Spectralon® 99% reflective panel. Parts of the averaged artificial light spectrum were merged with the averaged sunlight spectrum because atmospheric gases, e.g., water vapor, oxygen, and carbon dioxide, have strong absorption in parts of the measured wavelength region and the ASD spectrometers have low signal-to-noise ratio in parts of that wavelength range. To form the merged average absolute reflectance spectrum, segments of the averaged absolute reflectance from the artificial light measurements were scaled multiplicatively and merged with the averaged absolute reflectance from sunlight measurements. The merged spectrum is suitable for comparison with imaging spectrometer data across the full ASD wavelength range. At the field site, representative hand samples were collected. These samples were measured at the U.S. Geological Survey (USGS) laboratories in Denver, Colorado, using an ASD spectrometer. In this data release we provide the following data files in the specified formats; 1. Raw ASD spectrometer binary files recorded on the spectrometer in ASD Indico format (.asd files; Malvern Panalytical, 2018), 2. Latitude, longitude coordinates, date and UTC times of acquisition, and other metadata for all recorded field spectra in comma separated value (CSV) format (.csv extension) 3. Average of the reflected sunlight measurements in text file (.txt extension), 4. Average of the artificial light measurements in text file (.txt extension), 5. Merged sunlight/artificial light spectrum in text file (.txt extension), 6. Average of the laboratory measurements in text file (.txt extension), 7. Bounding polygon of field site in Zip-compressed Keyhole Markup Language (KMZ) and shapefile vector formats (.kmz and .shp extensions), 8. Various photos of the field site, measurement techniques, and sky conditions in Joint Photographic Experts Group (JPEG) format (.jpg files).

A full description of all collection and processing steps is included in this data release as: ‘SmithCreekPlayaNV_16aug2022_ProcessingSteps.pdf’. Reflectance data were collected using Malvern Panalytical ASD FieldSpec® 4 Hi-Res NG Spectroradiometers with custom VNIR gratings (hereafter referred to as ASD spectrometers) on August 16, 2022, at a field site in Smith Creek Valley, Nevada, USA. The ASD spectrometers used have a spectral range of 0.35 to 2.5 micronswith 2151 channels of data reported (Malvern Panalytical, 2018). Reflected sunlight was measured with the bare fiber (no fore optic), having a field of view of ~22 degrees, while traversing the area of the field site. Additional measurements of reflected artificial light were made at discrete sample points within the field site using an ASD Hi-Brite Contact Probe. Averages of relative reflectance spectra for the field site were computed separately from the sunlight and artificial light measurements. These averages were converted from relative reflectance to absolute reflectance by compensating for the absorption properties of the reference panel, a National Institute of Standards and Technology traceable Labsphere Spectralon® 99% reflective panel. Parts of the averaged artificial light spectrum were merged with the averaged sunlight spectrum because atmospheric gases, e.g., water vapor, oxygen, and carbon dioxide, have strong absorption in parts of the measured wavelength region and the ASD spectrometers have low signal-to-noise ratio in parts of that wavelength range. To form the merged average absolute reflectance spectrum, segments of the averaged absolute reflectance from the artificial light measurements were scaled multiplicatively and merged with the averaged absolute reflectance from sunlight measurements. The merged spectrum is suitable for comparison with imaging spectrometer data across the full ASD wavelength range. At the field site, representative hand samples were collected. These samples were measured at the U.S. Geological Survey (USGS) laboratories in Denver, Colorado, using an ASD spectrometer. In this data release we provide the following data files in the specified formats; 1. Raw ASD spectrometer binary files recorded on the spectrometer in ASD Indico format (.asd files; Malvern Panalytical, 2018), 2. Latitude, longitude coordinates, date and UTC times of acquisition, and other metadata for all recorded field spectra in comma separated value (CSV) format (.csv extension) 3. Average of the reflected sunlight measurements in text file (.txt extension), 4. Average of the artificial light measurements in text file (.txt extension), 5. Merged sunlight/artificial light spectrum in text file (.txt extension), 6. Average of the laboratory measurements in text file (.txt extension), 7. Bounding polygon of field site in Zip-compressed Keyhole Markup Language (KMZ) and shapefile vector formats (.kmz and .shp extensions), 8. Various photos of the field site, measurement techniques, and sky conditions in Joint Photographic Experts Group (JPEG) format (.jpg files).

A full description of all collection and processing steps is included in this data release as: ‘SmithCreekPlayaNV_16aug2022_ProcessingSteps.pdf’. Reflectance data were collected using Malvern Panalytical ASD FieldSpec® 4 Hi-Res NG Spectroradiometers with custom VNIR gratings (hereafter referred to as ASD spectrometers) on August 16, 2022, at a field site in Smith Creek Valley, Nevada, USA. The ASD spectrometers used have a spectral range of 0.35 to 2.5 micronswith 2151 channels of data reported (Malvern Panalytical, 2018). Reflected sunlight was measured with the bare fiber (no fore optic), having a field of view of ~22 degrees, while traversing the area of the field site. Additional measurements of reflected artificial light were made at discrete sample points within the field site using an ASD Hi-Brite Contact Probe. Averages of relative reflectance spectra for the field site were computed separately from the sunlight and artificial light measurements. These averages were converted from relative reflectance to absolute reflectance by compensating for the absorption properties of the reference panel, a National Institute of Standards and Technology traceable Labsphere Spectralon® 99% reflective panel. Parts of the averaged artificial light spectrum were merged with the averaged sunlight spectrum because atmospheric gases, e.g., water vapor, oxygen, and carbon dioxide, have strong absorption in parts of the measured wavelength region and the ASD spectrometers have low signal-to-noise ratio in parts of that wavelength range. To form the merged average absolute reflectance spectrum, segments of the averaged absolute reflectance from the artificial light measurements were scaled multiplicatively and merged with the averaged absolute reflectance from sunlight measurements. The merged spectrum is suitable for comparison with imaging spectrometer data across the full ASD wavelength range. At the field site, representative hand samples were collected. These samples were measured at the U.S. Geological Survey (USGS) laboratories in Denver, Colorado, using an ASD spectrometer. In this data release we provide the following data files in the specified formats; 1. Raw ASD spectrometer binary files recorded on the spectrometer in ASD Indico format (.asd files; Malvern Panalytical, 2018), 2. Latitude, longitude coordinates, date and UTC times of acquisition, and other metadata for all recorded field spectra in comma separated value (CSV) format (.csv extension) 3. Average of the reflected sunlight measurements in text file (.txt extension), 4. Average of the artificial light measurements in text file (.txt extension), 5. Merged sunlight/artificial light spectrum in text file (.txt extension), 6. Average of the laboratory measurements in text file (.txt extension), 7. Bounding polygon of field site in Zip-compressed Keyhole Markup Language (KMZ) and shapefile vector formats (.kmz and .shp extensions), 8. Various photos of the field site, measurement techniques, and sky conditions in Joint Photographic Experts Group (JPEG) format (.jpg files).

A full description of all collection and processing steps is included in this data release as: ‘SmithCreekPlayaNV_16aug2022_ProcessingSteps.pdf’. Reflectance data were collected using Malvern Panalytical ASD FieldSpec® 4 Hi-Res NG Spectroradiometers with custom VNIR gratings (hereafter referred to as ASD spectrometers) on August 16, 2022, at a field site in Smith Creek Valley, Nevada, USA. The ASD spectrometers used have a spectral range of 0.35 to 2.5 micronswith 2151 channels of data reported (Malvern Panalytical, 2018). Reflected sunlight was measured with the bare fiber (no fore optic), having a field of view of ~22 degrees, while traversing the area of the field site. Additional measurements of reflected artificial light were made at discrete sample points within the field site using an ASD Hi-Brite Contact Probe. Averages of relative reflectance spectra for the field site were computed separately from the sunlight and artificial light measurements. These averages were converted from relative reflectance to absolute reflectance by compensating for the absorption properties of the reference panel, a National Institute of Standards and Technology traceable Labsphere Spectralon® 99% reflective panel. Parts of the averaged artificial light spectrum were merged with the averaged sunlight spectrum because atmospheric gases, e.g., water vapor, oxygen, and carbon dioxide, have strong absorption in parts of the measured wavelength region and the ASD spectrometers have low signal-to-noise ratio in parts of that wavelength range. To form the merged average absolute reflectance spectrum, segments of the averaged absolute reflectance from the artificial light measurements were scaled multiplicatively and merged with the averaged absolute reflectance from sunlight measurements. The merged spectrum is suitable for comparison with imaging spectrometer data across the full ASD wavelength range. At the field site, representative hand samples were collected. These samples were measured at the U.S. Geological Survey (USGS) laboratories in Denver, Colorado, using an ASD spectrometer. In this data release we provide the following data files in the specified formats; 1. Raw ASD spectrometer binary files recorded on the spectrometer in ASD Indico format (.asd files; Malvern Panalytical, 2018), 2. Latitude, longitude coordinates, date and UTC times of acquisition, and other metadata for all recorded field spectra in comma separated value (CSV) format (.csv extension) 3. Average of the reflected sunlight measurements in text file (.txt extension), 4. Average of the artificial light measurements in text file (.txt extension), 5. Merged sunlight/artificial light spectrum in text file (.txt extension), 6. Average of the laboratory measurements in text file (.txt extension), 7. Bounding polygon of field site in Zip-compressed Keyhole Markup Language (KMZ) and shapefile vector formats (.kmz and .shp extensions), 8. Various photos of the field site, measurement techniques, and sky conditions in Joint Photographic Experts Group (JPEG) format (.jpg files).

A full description of all collection and processing steps is included in this data release as: ‘SmithCreekPlayaNV_16aug2022_ProcessingSteps.pdf’. Reflectance data were collected using Malvern Panalytical ASD FieldSpec® 4 Hi-Res NG Spectroradiometers with custom VNIR gratings (hereafter referred to as ASD spectrometers) on August 16, 2022, at a field site in Smith Creek Valley, Nevada, USA. The ASD spectrometers used have a spectral range of 0.35 to 2.5 micronswith 2151 channels of data reported (Malvern Panalytical, 2018). Reflected sunlight was measured with the bare fiber (no fore optic), having a field of view of ~22 degrees, while traversing the area of the field site. Additional measurements of reflected artificial light were made at discrete sample points within the field site using an ASD Hi-Brite Contact Probe. Averages of relative reflectance spectra for the field site were computed separately from the sunlight and artificial light measurements. These averages were converted from relative reflectance to absolute reflectance by compensating for the absorption properties of the reference panel, a National Institute of Standards and Technology traceable Labsphere Spectralon® 99% reflective panel. Parts of the averaged artificial light spectrum were merged with the averaged sunlight spectrum because atmospheric gases, e.g., water vapor, oxygen, and carbon dioxide, have strong absorption in parts of the measured wavelength region and the ASD spectrometers have low signal-to-noise ratio in parts of that wavelength range. To form the merged average absolute reflectance spectrum, segments of the averaged absolute reflectance from the artificial light measurements were scaled multiplicatively and merged with the averaged absolute reflectance from sunlight measurements. The merged spectrum is suitable for comparison with imaging spectrometer data across the full ASD wavelength range. At the field site, representative hand samples were collected. These samples were measured at the U.S. Geological Survey (USGS) laboratories in Denver, Colorado, using an ASD spectrometer. In this data release we provide the following data files in the specified formats; 1. Raw ASD spectrometer binary files recorded on the spectrometer in ASD Indico format (.asd files; Malvern Panalytical, 2018), 2. Latitude, longitude coordinates, date and UTC times of acquisition, and other metadata for all recorded field spectra in comma separated value (CSV) format (.csv extension) 3. Average of the reflected sunlight measurements in text file (.txt extension), 4. Average of the artificial light measurements in text file (.txt extension), 5. Merged sunlight/artificial light spectrum in text file (.txt extension), 6. Average of the laboratory measurements in text file (.txt extension), 7. Bounding polygon of field site in Zip-compressed Keyhole Markup Language (KMZ) and shapefile vector formats (.kmz and .shp extensions), 8. Various photos of the field site, measurement techniques, and sky conditions in Joint Photographic Experts Group (JPEG) format (.jpg files).