Solid bitumen is widely used as a thermal proxy in source-rock reservoirs, yet its texture and presentation may be affected by varying environmental constraints during its formation, e.g., water concentration, mineral catalysis, or salinity. Herein we investigated the development of solid bitumen properties during artificial maturation using three diverse (lacustrine to marine) oil shale samples containing abundant H-rich sedimentary organic matter (bituminite). Bituminite in the oil shales was treated via pyrolysis (320°C, 72 hrs) using hydrous, anhydrous, and brine conditions, causing the development of a newly formed solid bitumen in the experiment residues. The properties of the newly formed solid bitumen then were evaluated via geochemical screening tests, optical and electron microscopy, and infrared spectroscopy. Experimental residues also were treated via solvent extraction, allowing characterization of the effects of extraction to solid bitumen. Data from the experiments are provided here in 5 tables. Table 1 contains extract and fractionation data for untreated samples. Table 2 contains gas chromatography ratios. Table 3 contains reflectance and geochemical screening data. Table 4 contains gas yields for each sample under the various conditions. Table 5 contains Micro-Fourier transform infrared (micro-FTIR) data. For analysis findings, interpretations, and results, refer to the accompanying larger work publication, "Properties of solid bitumen formed during hydrous, anhydrous, and brine pyrolysis of oil shale: implications for solid bitumen reflectance in source-rock reservoirs".

This study tests the influence of environmental conditions on conversion of the maceral bituminite to a solid petroleum residuum (solid bitumen) during pyrolysis. The presence of water in sedimentary basins controls multiple processes during petroleum generation, migration, and storage. Four organic-rich (26–36 wt.% total organic carbon) oil shale samples were collected from thin-bedded (several cm thick), discontinuous outcrop exposures in the Neoproterozoic–Lower Cambrian restricted marine Salt Range Formation in the upper Indus Basin, Pakistan. Samples were from the Khewra Gorge (K-2) and Sohan Nala localities [SN-R(c), SN-5(b), SN-1]; a sample of Joadja torbanite coal from Australia containing terrigenous vitrinite was also included in the study for comparison. All samples were crushed, homogenized, and sieved to 4 (4.75 mm) or 8 (2.36 mm) mesh prior to pyrolysis experiments. Experiments used closed system batch reactors at subcritical water temperatures between 300 and 370°C for 72 hrs. The samples were pyrolyzed under hydrous and anhydrous conditions using distilled water, brine, or the absence of fluid as a condition of the experiment. These data tables represent the findings of this study and support an upcoming publication.

This study tests the influence of environmental conditions on conversion of the maceral bituminite to a solid petroleum residuum (solid bitumen) during pyrolysis. The presence of water in sedimentary basins controls multiple processes during petroleum generation, migration, and storage. Four organic-rich (26–36 wt.% total organic carbon) oil shale samples were collected from thin-bedded (several cm thick), discontinuous outcrop exposures in the Neoproterozoic–Lower Cambrian restricted marine Salt Range Formation in the upper Indus Basin, Pakistan. Samples were from the Khewra Gorge (K-2) and Sohan Nala localities [SN-R(c), SN-5(b), SN-1]; a sample of Joadja torbanite coal from Australia containing terrigenous vitrinite was also included in the study for comparison. All samples were crushed, homogenized, and sieved to 4 (4.75 mm) or 8 (2.36 mm) mesh prior to pyrolysis experiments. Experiments used closed system batch reactors at subcritical water temperatures between 300 and 370°C for 72 hrs. The samples were pyrolyzed under hydrous and anhydrous conditions using distilled water, brine, or the absence of fluid as a condition of the experiment. These data tables represent the findings of this study and support an upcoming publication.

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).

Solid bitumen is a petrographically-defined secondary organic matter residue produced during petroleum generation and subsequent oil transformation. The presence of solid bitumen impacts many shale reservoir properties including porosity, permeability, and hydrocarbon generation and storage, amongst others. Furthermore, solid bitumen reflectance is an important parameter for assessing the thermal maturity of formations with little to no vitrinite. While the molecular composition of solid bitumen will strongly impact associated parameters such as the development of organic matter porosity, hydrocarbon generation, and optical reflectance, assessing the molecular composition of solid bitumen in situ within shale reservoirs can be challenged by small grain sizes (often 1 m in diameter) and the inherent heterogeneity of shale formations. Here we employ the recently developed atomic force microscopy-based infrared spectroscopy (AFM-IR) to investigate solid bitumen molecular composition in situ within shale samples from the Late Cretaceous Eagle Ford Group possessing Type II-S kerogen that span a natural thermal maturity gradient from early oil-generation to the dry gas window. The application of AFM-IR allows for the rapid collection of thousands of measurements with ~50 nm resolution from the interrogated solid bitumen grains. Our results indicate that: (i) solid bitumen from the lower Eagle Ford displays both intra- and intergranular molecular variation, (ii) this molecular variation tends to, but not universally, decrease with an increase in thermal maturity, and (iii) the solid bitumen composition between samples, from an atomic ratio perspective, is more similar than analysis of kerogen isolates would indicate. These findings are discussed with perspective toward understanding the impact of thermal stress on the composition of secondary organic matter within the Eagle Ford Shale and highlight the growing awareness that organic matter heterogeneity within petroliferous mudrocks extends down to the nanoscale regime.

Solid bitumen is a petrographically-defined secondary organic matter residue produced during petroleum generation and subsequent oil transformation. The presence of solid bitumen impacts many shale reservoir properties including porosity, permeability, and hydrocarbon generation and storage, amongst others. Furthermore, solid bitumen reflectance is an important parameter for assessing the thermal maturity of formations with little to no vitrinite. While the molecular composition of solid bitumen will strongly impact associated parameters such as the development of organic matter porosity, hydrocarbon generation, and optical reflectance, assessing the molecular composition of solid bitumen in situ within shale reservoirs can be challenged by small grain sizes (often 1 m in diameter) and the inherent heterogeneity of shale formations. Here we employ the recently developed atomic force microscopy-based infrared spectroscopy (AFM-IR) to investigate solid bitumen molecular composition in situ within shale samples from the Late Cretaceous Eagle Ford Group possessing Type II-S kerogen that span a natural thermal maturity gradient from early oil-generation to the dry gas window. The application of AFM-IR allows for the rapid collection of thousands of measurements with ~50 nm resolution from the interrogated solid bitumen grains. Our results indicate that: (i) solid bitumen from the lower Eagle Ford displays both intra- and intergranular molecular variation, (ii) this molecular variation tends to, but not universally, decrease with an increase in thermal maturity, and (iii) the solid bitumen composition between samples, from an atomic ratio perspective, is more similar than analysis of kerogen isolates would indicate. These findings are discussed with perspective toward understanding the impact of thermal stress on the composition of secondary organic matter within the Eagle Ford Shale and highlight the growing awareness that organic matter heterogeneity within petroliferous mudrocks extends down to the nanoscale regime.

This study presents Raman spectroscopic data paired with scanning electron microscopy (SEM) to assess solid bitumen composition and porosity development as a function of solid bitumen texture and association with minerals. A series of hydrous pyrolysis experiments (1-103 days, 300-370°C) using a low maturity (0.25% solid bitumen reflectance, BRo), high total organic carbon [(TOC), 14.0 wt. %] New Albany Shale sample as the starting material yielded pyrolysis residues designed to evaluate the evolution of TOC, solid bitumen aromaticity, and organic porosity development with increasing temperature and heating duration. Solid bitumen was analyzed by Raman spectroscopy wherein point data was collected from accumulations that ranged in size, pore density, and degree of association with the mineral matrix. Raman spectroscopy results show that with increasing temperature and experimental duration, solid bitumen aromaticity increases and compositional variability decreases. With regards to texture and composition, coarser-grained solid bitumen (>1.3 µm from nearest mineral grain) tends to have fewer pores (as identified with SEM) and consistently higher, but less variable aromaticity than thinner, wispy solid bitumen which is more intimately associated with the mineral matrix. The Raman data indicate that solid bitumen porosity development and molecular composition are linked, and these parameters are related to the textural relationships of the organic matter within the whole rock.

This study presents Raman spectroscopic data paired with scanning electron microscopy (SEM) to assess solid bitumen composition and porosity development as a function of solid bitumen texture and association with minerals. A series of hydrous pyrolysis experiments (1-103 days, 300-370°C) using a low maturity (0.25% solid bitumen reflectance, BRo), high total organic carbon [(TOC), 14.0 wt. %] New Albany Shale sample as the starting material yielded pyrolysis residues designed to evaluate the evolution of TOC, solid bitumen aromaticity, and organic porosity development with increasing temperature and heating duration. Solid bitumen was analyzed by Raman spectroscopy wherein point data was collected from accumulations that ranged in size, pore density, and degree of association with the mineral matrix. Raman spectroscopy results show that with increasing temperature and experimental duration, solid bitumen aromaticity increases and compositional variability decreases. With regards to texture and composition, coarser-grained solid bitumen (>1.3 µm from nearest mineral grain) tends to have fewer pores (as identified with SEM) and consistently higher, but less variable aromaticity than thinner, wispy solid bitumen which is more intimately associated with the mineral matrix. The Raman data indicate that solid bitumen porosity development and molecular composition are linked, and these parameters are related to the textural relationships of the organic matter within the whole rock.

Solid organic matter (OM) in sedimentary rocks produces petroleum and solid bitumen when it undergoes thermal maturation. The solid OM is a ‘geomacromolecule’, usually representing a mixture of various organisms with distinct biogenic origins, and can have high heterogeneity in composition. Programmed pyrolysis is a common conventional method to reveal bulk geochemical characteristics of the dominant OM while detailed organic petrography is required to reveal information about the biogenic origin of contributing macerals. Despite advantages of programmed pyrolysis, it cannot provide information about the heterogeneity of chemical compositions present in the individual OM types. Therefore, other analytical techniques such as Raman spectroscopy are necessary. In this study, we compared geochemical characteristics and Raman spectra of two sets of naturally and artificially matured Bakken source rock samples. A continuous Raman spectral map on solid bitumen particles was created from the artificially matured hydrous pyrolysis residues, in particular, to show the systematic chemical modifications in microscale. Spectroscopy data was plotted for both sets against thermal maturity to compare maturation rate/path for these two separate groups. The outcome showed that artificial maturation through hydrous pyrolysis does not follow the same trend as naturally-matured samples although having similar solid bitumen reflectance values (%SBRo). Furthermore, Raman spectroscopy of solid bitumen from artificially matured samples indicated the heterogeneity of OM decreases as maturity increases. This represents an alteration in chemical structure towards more uniform compounds at higher maturity. This study may signify the potential of Raman spectroscopy as an alternative to the conventional (pseudo) Van Krevelen diagram, by revealing the underlying chemical changes. Finally, observation by Raman spectroscopy of chemical alteration of OM during artificial maturation may assist in the proposal of improved pyrolysis protocols to better resemble natural geologic processes.