Illinois Basin Research Articles

Association of uranium with macerals in marine black shales: Insights from the Upper Devonian New Albany Shale, Illinois Basin

Marine organic-rich shales generally have high uranium content associated with sedimentary organic matter. However, organic matter in black shales is not homogeneous, but instead a mixture of different macerals. The uranium content and organic petrographic composition of 27 New Albany Shale samples indicate differential contributions of macerals to the uranium content in the Upper Devonian New Albany Shale of the Illinois Basin. Specifically, uranium is mainly associated with amorphous organic matter (microbially degraded phytoplankton, zooplankton, and bacterial biomass), where an average uranium content of approximately 550 ppm has been estimated. The amorphous organic matter's lack of structure, as well as admixed with mineral grains (<7.8 μm) suggest that it originated via microbial degradation in surficial sediments. Uranium may have been incorporated into amorphous organic matter during phytoplankton degradation and amorphous kerogen formation early in diagenesis. Pore-water redox conditions and pH control the reduction of uranium (VI) and its incorporation into amorphous organic matter. Alginite derived from Tasmanites algae (average uranium content <10 ppm) contributes minimally to uranium content. Terrestrial organic matter in the New Albany Shale contains on average ~ 20 ppm uranium, and because it accounts for <10% of total organic matter in the New Albany Shale, its contribution is equally negligible.

Application of pXRF elemental analysis and organic petrography in correlation of Pennsylvanian strata: An example from the Indiana part of the Illinois Basin, USA

The principal purpose of this research is to investigate whether elemental chemistry obtained by a portable X-ray fluorescence (pXRF) analyzer can aid in correlating lithostratigraphic units within the Pennsylvanian coal-bearing sequence of the eastern part of the Illinois Basin in Indiana. The study is based on data collected from four boreholes: Indiana Geological and Water Survey wells SDH-377 in Daviess County, SDH-379 in Pike County, SDH-383 in Posey County, and SDH-43 in Warrick County. The organic-matter-rich marine black shales and limestones are our special targets because they may represent valuable marker beds. Highly elevated U and Mo concentrations can be utilized to clearly identify the stratigraphic positions of the organic-matter-rich marine black shales in the succession from the oldest to the youngest: Sh1, Sh2, Sh3, and Sh4. Increased concentrations of both U and Mo provide further evidence for the deposition of these shales in anoxic environments. Variations in Ca and Mg concentrations aid in identifying limestone and dolomitic limestone horizons through the interval. Although the positions of marine shales and limestone strata were clearly defined based on pXRF data, identifying specific shales or limestones was problematic because of the wide elemental variations that exist within individual horizons. To help overcome this difficulty, reflected light microscopy was used as complementary technique on shale samples. These shales represent early oil window maturity(vitrinite reflectance 0.56 to 0.58%) and their organic matter is dominated by low-reflectance amorphous organic matter (AOM) and high-reflectance micrinized AOM. Well-preserved alginite, vitrinite, inertinite, and solid bitumen are rare. Our results show that proportions of low-reflectance AOM and micrinized AOM and framboidal pyrite content are promising characteristics that may help to identify individual shales. Specifically, Sh1 and Sh4 are dominated by low-reflectance AOM, whereas the other two shales have micrinized AOM as the dominant component. Sh2 and Sh4 have consistently high framboidal pyrite content.

Rare Earth Elements and Yttrium (REY) in coal mine drainage from the Illinois Basin, USA

The ever-growing demand in the USA and in the modern economy for rare earth elements, defined here as the lanthanide elements plus yttrium (REY), motivates the development of economically feasible and environmentally friendly approaches for domestic REY resources. Non-conventional sources, including coal mine drainage (CMD) hosting elevated concentrations of REY, have been explored as attractive secondary sources for metals recovery. Consequently, in this study we investigate CMD from abandoned coal mines in the Illinois Basin as a potential REY resource.We collected CMD from 35 abandoned coal mine sites in the Illinois Basin and investigated trends in REY enrichment and their association with CMD geochemical characteristics, including pH, the presence of other chemical elements of economic significance (i.e., Zn, Ni, Cr, Cu, V) as well as spatial patterns in relation to Permian magmatic intrusions of the Hicks Dome, a potential source of REY in the Illinois Basin. Additionally, the REY contents in possible source rocks for Illinois CMD were measured including coal from an underground mine and coal preparation plant in southern Illinois, mafic igneous rocks associated with Hicks Dome, and hydrothermal fluorite from Illinois fluorspar district.The REY concentrations in samples of CMD (filtered fraction) and associated coal and non-coal solids were determined by ICP-MS. The total concentration of REY in CMD, ΣREYCMD varied between 1 and 9879 μg/L with an average of 1059 μg/L and critical-ΣREYCMD (Nd, Eu, Tb, Dy, and Y) varied between 0.3 and 7212.5 μg/L with an average of 611 μg/L. Basin-wide, we found no statistical correlation between ΣREYCMD and (1) pH of the CMD, or (2) proximity to the Permian magmatic intrusion at Hicks Dome in southern Illinois. The REYCMD values normalized to North American Shale Composite (NASC) REYCMD/REYNASC exhibit enrichments in middle-REY for all CMD, but also enrichments in light-REY in some CMD. Statistically, we observed that ΣREYCMD displays significant direct correlations with Al, Si, SO4, Zn, Ni, Co, and Cu and no-correlation with Fe, Ca, PO4, Ba, and V.Synthesis of the geochemical data suggests that coal mining sites with the highest ΣREYCMD and critical-ΣREY contents include non-coal bedrock dominated by silicates (high clay content) and coal mine wastes that were impacted by metal-rich hydrothermal solutions, which are predominantly located along the western and northern margins of the Illinois Basin. Particularly, sites with the highest hydrothermal input as approximated by Mississippi Valley-type mineralization (i.e., Zn contents) are prime candidates for REY, as well as other elements of potential economic value such as Al, Ni, Cr, V, and Co. Thus, CMD in the Illinois Basin could become a potential alternative domestic source of extractable REY, especially critical-ΣREY, as well economically valuable metals.

Detrital Zircon Geochronologic Constraints on Patterns and Drivers of Continental‐Scale Sediment Dispersal in the Late Mississippian

AbstractThe Late Mississippian was a critical time interval in Laurentia's history, marking the transition from carbonate deposition on a stable platform, during the Early to Middle Mississippian, to extensive clastic deposition in the Pennsylvanian to Permian associated with the Laurentia‐Gondwana collision. In the U.S. midcontinent, Chesterian incised valley fill (IVF) systems that developed within a carbonate‐dominated platform provide new insights on the patterns and drivers of continental‐scale sediment dispersal during this transitional period. Here we report 1,037 new concordant detrital zircon U‐Pb ages from nine samples of Uppper Mississippian sandstone collected from cores in southwestern Kansas and from outcrops in northwestern Arkansas. The sandstones are characterized by major age clusters corresponding to the Grenville (900–1,300 Ma) and Taconic‐Acadian (350–500 Ma) orogenies and minor older age groups, suggesting derivation from the Appalachian region. A compilation of published detrital zircon ages from Early Paleozoic sandstones as well as from temporally equivalent units across North America, including from the Appalachian Foreland Basin, Illinois Basin, Arkoma Shelf, Ozark Dome, Black Warrior Basin, and Grand Canyon, suggests Chesterian sandstone age distributions are distinct from those of older sandstones and are consistent with a change to a dominantly Appalachian age signature that was roughly synchronous across the continent. Together, the new and compiled ages support development of a generally E‐W transcontinental sediment dispersal system in the Late Mississippian that was likely controlled by orogenesis on the eastern Laurentian margin, while local variations in the age signatures appear to be controlled by N‐S drainage networks, influenced by glacioeustatic fluctuations and local structures.

Sensitivity thresholds of groundwater parameters for detecting CO2 leakage at a geologic carbon sequestration site.

Geologic carbon sequestration (GCS) projects in the USA are required to monitor groundwater quality for geochemical changes above the injection area that may be a result of CO2 or brine leakage from the storage reservoir. Should CO2 migrate into the groundwater around the compliance wells monitoring the shallower hydrologic units, each compliance parameter could react differently depending on its sensitivity to CO2. Statistically determined limits (SDLs) for detection of CO2 leakage into groundwater were calculated using background water quality data from the Illinois Basin Decatur Project (IBDP) sequestration site and prediction and tolerance intervals for specific compliance parameters. If the parameter concentrations varied outside of these ranges during the injection and post injection periods of a GCS project, then additional actions would be required to determine the reason for the changes in groundwater concentrations. Geochemical modeling can simulate the amount of CO2 needed to alter water quality parameters a statistically significant amount. This information can then inform GCS operators and regulators as to which compliance parameters are relevant (sensitive) to CO2 leakage for a given setting. For the system studied in here, Fe, Ca, K, Mg, CO2, and pH were sensitive to CO2 addition while Al, Cl, Na, and Si were not.

Variability of rock mechanical properties in the sequence stratigraphic context of the Upper Devonian New Albany Shale, Illinois Basin

Abstract Rock mechanical properties of tight shale reservoirs are important parameters in the exploration and development of unconventional shale oil and gas. Understanding the stratigraphic variability of rock mechanical properties in black shale successions is important for identifying promising intervals for hydraulic stimulation. High-resolution hardness tests (6 cm spacing) with an Equotip Bambino 2 hardness tester were conducted on a New Albany Shale core to study the stratigraphic variability of rock mechanical properties. Combined with high-resolution geochemical analyses (8 cm spacing) acquired with a portable X-ray fluorescence spectrometer, it is possible to relate hardness variability to shale composition. The results of our study suggest an average quartz content of about 28% for the entire succession. Approximately half of that amount (13%) is interpreted to be of biogenic origin. Biogenic quartz, mainly derived from dissolution of radiolaria, occurs as authigenic quartz precipitated in Tasmanites cysts, and as microcrystalline quartz precipitated in the shale matrix. Petrographic observations indicate that the hardness of the New Albany Shale is critically controlled by biogenic quartz content, not by total quartz content as suggested in multiple prior studies. Biogenic quartz forms an interconnected stiff framework which increases the hardness of shales. In contrast, dispersed “hard” grains (e.g., detrital quartz, feldspar, and dolomite) do not contribute to brittle behavior. When examined under a scanning electron microscope, “hard” shales are rich in biogenic quartz and contrast visibly with “soft” shales that are characterized by high contents of clay minerals. Negative correlation between hardness and Al2O3 content, as well as differential compaction of clay minerals around “hard” grains, indicate that clay minerals are an important ductile component in the New Albany Shale. Although the general softness of kerogen suggests that there should be an influence of organic matter on hardness, this effect is counteracted by biogenic quartz cementation which has a comparable stratigraphic distribution pattern. We propose a new mineral-composition-based brittleness index on the basis of biogenic quartz content to characterize the brittleness of tight shale reservoirs. Within a sequence stratigraphic context, the hardness of the New Albany Shale increases in transgressive systems tracts, reaches a maximum at maximum flooding surfaces, and decreases in highstand systems tracts with the exception of the Blocher Member. Maximum flooding surface intervals have the highest potential to develop brittle fractures and should be potential targets for hydraulic stimulation.

Palynology, organic petrology and geochemistry of the Bell coal bed in Western Kentucky, Eastern Interior (Illinois) Basin, USA

The Bell coal bed is one of the stratigraphically oldest coals (Atokan, Duckmantian) in the Illinois Basin that has been commercially mined and occurs near the Morrowan-Atokan boundary, which was a time of significant lithologic change in the basin. The Bell coal occurs as a series of discontinuous pods, in contrast to younger (Asturian) coals in the basin that are thicker and more extensive in occurrence. Thirty-two samples of coal and carbonaceous shale, collected from surface mine, outcrop, and drill core locations were analyzed geochemically, petrographically and palynologically to ascertain the origin of the Bell coal bed in western Kentucky.The Bell coal exhibits a great deal of variability in thickness and composition, both temporally and spatially. Based on ash yields, the Bell coal consists of intercalated layers of coal (≤25% ash), impure coal (>25 to <50% ash) and carbonaceous shale (≥50% ash). Sulfur contents vary significantly, from 0.2% to 10.0%. Petrographically, the Bell coal is mainly a high vitrinite coal (>80%, mmf), with telovitrinite occurring more frequently than detrovitrinite and gelovitrinite. Certain layers, however, contain elevated amounts of liptinite and inertinite. Among the inertinite macerals, examples of both fire (e.g., fusinite) and degradation (e.g., macrinite) origin are evident. Samples with elevated amounts of inertinite are commonly, though not exclusively, high in ash, indicating that some of the inertinite may be of allochthonous origin.Palynologically, the Bell coal is dominated by arborescent lycopod spores (avg. >70%), occurring primarily as Lycospora, with some samples containing increased proportions of spores and pollen from other Pennsylvanian plant groups. Samples with more heterogenous palynofloras commonly have elevated ash yields, indicating that some portion of the assemblages may be also of allochthonous origin.Collectively, the Bell coal is interpreted to have formed from a series of small, disconnected paleomires that were planar and topogenous with paleotopography having an influence on peat development. A planar, topogenous origin helps to explain the highly variable ash yields and sulfur contents. Accumulating peat, principally from arborescent lycopod source material, was mainly well-preserved, but punctuated with intervals marked by sediment influx, the development of more heterogeneous palynofloras and degradation and oxidation of the surficial peat by both biologic (decay) and abiotic (fire) processes.

Water Vapor Sorption Properties of Illinois Shales Under Dynamic Water Vapor Conditions: Experimentation and Modeling

AbstractWater vapor adsorption/desorption isotherms are measured on five shales from Illinois basin by dynamic vapor sorption method. The experimental adsorption data are modeled by the Guggenheim, Anderson, and De Boer model and the Freundlich model over the entire range of measured relative humidity (Rh) values (0–0.95). Modeling results show that shale hydration is controlled by surface chemistry at low Rh through a strong intermolecular bonding, while is mainly influenced by the pore structure at high Rh (&gt;0.9) through capillary condensation. This is consistent with the progressive decrease of isosteric heat of adsorption with water content, obtained by the Clausius‐Clapeyron equation. Exceptionally, for the one shale containing 8.6% montmorillonite, mesopore condensation only accounts for 33% of the measured water adsorption even at Rh ~0.95 due to the limited external pores and the important role of clay swelling. The specific surface area defined by Guggenheim, Anderson, and De Boer analysis as available for water adsorption is larger than that available for low‐pressure N2 adsorption due to the complex surface chemistry. The one shale rich in expansive montmorillonite and with a large interlayer capacity for water but inaccessible to N2 molecules conditions this result. Among the other four shales, one with high kerogen content behaves the highest water adsorption, possibly due to the high content of oxygen‐containing functional groups and the potentially high pore volume of kerogen. These findings contribute to a better understanding of water storage and transport behavior in shales and impact behavior relevant to structures and reservoirs founded in such media.

Omphalophloios wagneri sp. nov., a new sub-arborescent lycopsid from the middle Moscovian (Middle Pennsylvansian) of the Illinois Basin, USA

Described is a new species of sub-arborescent lycopsid, Omphalophloios wagneri sp. nov. from roof shale of the middle Moscovian (Bolsovian/Atokan) (Middle Pennsylvanian) Lower Block Coal in the Illinois Basin, Indiana, USA. Available material represents mostly fragments of 16 to >60 mm wide fertile axes that bear densely spaced sporangia, which are flattened due to compaction into disc-like shape, 2.5–3.1 mm in diameter. The outer sporangial cell wall layer displays a gradual transition from isometric cells in the central parts of adaxial and abaxial sporangial valves, to a narrow belt of elongated cells in the equatorial area, interpreted as a dehiscence zone. Micro- and megasporangia alternate in irregular patches, a single sporangium being attached adaxially to an extended sporophyll base. Cyperites-like sporophyll distal laminae are ~25 mm long at fertile shoot apices but become progressively longer (>110 mm) down the shoots. Based on size distribution of stems, fertile shoots are estimated to bifurcate at least five times, which suggests that O. wagneri formed a relatively dense crown. The entire habit of the plant is difficult to assess from existing material; however, the tree was probably small and interpreted as colonizing low lying to slightly raised peat swamps. Omphalophloios wagneri differs from all other adpression-based species of the genus in having the smallest sporangia and several orders of fertile-axis bifurcations. In situ megaspores of the Zonalesporites brassertii type also are different from all other Omphalophloios megaspores.

Petrology, geochronology, and geophysical characterization of Mesoproterozoic rocks in central Illinois, USA

The Precambrian basement rocks of the Eastern Granite-Rhyolite Province (EGRP) in central Illinois (midcontinent region of North America) exhibit a complex history of early volcanism, granite emplacement, and intrusion of mafic rocks. A comprehensive suite of dedicated petrographic analyses, geophysical logs, and drill core from four basement-penetrating wells, two-dimensional and three-dimensional seismic reflection data, and U-Pb age data from the Illinois Basin–Decatur Project (IBDP) and Illinois Carbon Capture Storage (ICCS) Project site provide new constraints for interpreting the Precambrian basement of the Illinois Basin. These new data reveal the basement to be compositionally and structurally complex, having typical EGRP felsic volcanic rocks intruded by the first reported gabbro in the Precambrian basement in Illinois. Zircons (n ​= ​29) from rhyolite give a U-Pb weighted mean average age of 1467 ​± ​9 ​Ma. Zircons (n ​= ​3) from a gabbro dike that intrudes the rhyolite yield a concordia age of 1073 ​± ​12 ​Ma, which corresponds to Grenville-age extension and represents the first Grenville-age rock in Illinois and in the EGRP. A high-resolution three-dimensional seismic reflection volume, coincident with the four wells, provides a context for interpreting the petrological data and implies a high degree of heterogeneity for basement rocks at the IBDP–ICCS site, as also shown by the drill cores. The occurrence of Grenville-age gabbro is related to a prominent bowl-like structure observed on local two-dimensional seismic reflection profiles and the three-dimensional volume that is interpreted as a deep-seated mafic sill complex. Furthermore, heterogeneities such as the brecciated EGRP rhyolite and later gabbro intrusion observed in the basement lithology at the IBDP–ICCS may reflect previously unknown distal elements of the 1.1 ​Ga Midcontinent Rift in the EGRP and more likely Grenville-age extension.

Pn Tomography and Anisotropy Study of the Central United States

AbstractDetailed P wave velocity and anisotropy structure of the uppermost mantle below the central United States is presented based on a tomographic inversion of Pn traveltimes for earthquakes in the range 2 to 14°. Dense raypath coverage throughout the northern Mississippi Embayment is obtained using the Northern Embayment Lithosphere Experiment and U.S. Transportable Array data sets. A detailed analysis of the trade‐off between velocity and anisotropy variations demonstrates that both are well resolved over most of the study area. Anomalously fast Pn velocities are identified below the northern Mississippi Embayment, centered on the New Madrid seismic zone. A prominent region of low velocity coincides with the southwestern margin of the Illinois basin. Pn anisotropy displays complex patterns and differs from absolute plate motion directions and SKS splitting directions. A circular pattern of fast anisotropy directions is centered on the New Madrid seismic zone and may be related to the presence of the mafic “rift pillow.”

Soil gas monitoring at the Illinois Basin – Decatur Project carbon sequestration site

An extensive monitoring, verification, and accounting (MVA) program was carried out from 2011 to 2016 as part of the Illinois Basin – Decatur Project (IBDP), a large-scale carbon capture and storage (CCS) demonstration project in Decatur, Illinois, USA. As part of the monitoring program, a near-surface monitoring network for soil gas was used to characterize the natural variability of CO2 and identify anomalies that could be associated with CO2 leakage in the vadose zone. In the fall of 2011, 21 permanent soil gas sampling nests were installed on-site and three nests were installed off-site as reference locations. Soil gas was collected from three depth intervals (15–30, 47–61, 107–122 cm) at each nest. Fixed gas (CO2, N2, O2, and light hydrocarbon) concentrations, stable carbon isotopic composition (δ13C), and radiocarbon (14C) content of CO2 in soil gas were monitored during the pre-injection, injection, and post-injection phases from 2011 to 2016. Both CO2 concentrations and carbon isotopic compositions showed large spatial and temporal variations; however, the relationships among CO2, N2, and O2 concentrations in soil gas indicated that these variations should be attributed to natural processes and not CO2 leakage. Soil CO2 concentrations responded to temperature and precipitation variations and increased with increasing soil depth. While 14C cannot be used to determine the occurrence of CO2 leakage at IBDP site due to the indistinctive signature between injected CO2 and soil gas CO2, experiences at IBDP validated that δ13C can serve as an effective natural tracer at this site. Results from this project have value for future industrial CCS projects that plan to use soil gas monitoring techniques for site characterization and leakage detection.

Integrated Approaches to Explore the Biosphere Inhabiting the Deep Subsurface of the Illinois Basin, USA

Integrated Approaches to Explore the Biosphere Inhabiting the Deep Subsurface of the Illinois Basin, USA

A Detailed Approach for Cost Analysis for Early CCS Projects: A Case Study from the Illinois Basin - Decatur Project

A Detailed Approach for Cost Analysis for Early CCS Projects: A Case Study from the Illinois Basin - Decatur Project

An Operations Perspective on Injectivity and Capacity

Injectivity and capacity are two of the most important criteria of a CO2 storage site’s screening and selection process. A geologic formation can be characterized directly to quantify injectivity and capacity via the permeability-thickness and porosity- thickness products, respectively. After a project starts, the importance of each to the project is slightly different. Maintaining injection rate is one primary challenge during active injection operations, while the long-term storage capacity is one primary challenge to the storage project. For specific projects, the daily injection rate of CO2 and the ultimate storage quantity desired are based on the capture and compression facility, and the CO2 source is the driver to determine the mandatory qualifications of a site. Injectivity is defined as the ratio of the injection rate to the pressure change between the well and the storage zone, which is proportional to the permeability-thickness product. The initial start-up and subsequent start-ups of CO2 injection following short and extended shut-in periods are ideal times for multirate CO2 injection. These injection tests performed periodically can show injectivity behavior over longer periods of time so that the trends of the injection interval response can be analyzed and projected for longer terms when a stimulation or another sub-interval perforation may be required for injection. Because rate and pressure are generally direct measurements, injectivity-time, rate-pressure-time, and rate-pressure relationships can be used to diagnose trends in injection operations that are not apparent from injection rate alone. Capacity is defined as a quantity (mass or volume) of CO2 that can be injected and stored in a specific geologic formation from a specific injection project; it is proportional to porosity-thickness product. While permeability and capillary pressure are not part of the capacity calculation, both properties determine the accessibility of the porosity to injected CO2, hence the part of the pore space that can be used for storage. Furthermore, local geologic heterogeneity and architecture will strongly influence petrophysical flow properties and determine the plume size and shape. Storage efficiency has been used to define the fraction of the pore volume (or bulk volume) in which CO2 can be stored. It includes geologic (e.g. ratio of net to gross thickness), macroscopic (e.g. gravity), and microscopic (e.g. saturation) terms. It is relatively simple to quantify capacity if the location and distribution of CO2 is not required; however, if approximate dimensions of CO2 plume is necessary, it is very difficult to quantify confidently capacity. Prior to CO2 injection, statistical methods, numerical simulation, and a limited number of analytical methods are available. During injection, the most direct measurement is cased hole logging (e.g. neutron capture logs), which only measures very near wellbore CO2 saturation above a threshold saturation (e.g. 5%). Once the CO2 plume area, thickness, and saturation are adequate to make a detectable seismic contrast, a seismic survey may be helpful, but it detects only the thicker and higher CO2 saturation parts of the plume. Real-time analyses of injectivity and capacity during CO2 injection can provide operators with information necessary to plan for contingencies that increase certainty and meet the CO2 project goals. During site screening and selection, project risk can be reduced, but only after actual CO2 injection can these properties be more convincingly estimated. Injection operation results and observations, from the US Department of Energy sponsored Illinois Basin Decatur Project at Decatur, Illinois, USA, are used to demonstrate changes in injectivity and capacity through time and their influence on operations.

Conodont biostratigraphy and magnetic susceptibility of Upper Devonian Chattanooga Shale, eastern United States: Evidence for episodic deposition and disconformities

Recognition of stratigraphic hiatuses in fine-grained siliciclastic sedimentary rocks can be challenging but is feasible using high-resolution biostratigraphic and chemostratigraphic data within a regional correlation framework. In this case study of the Upper Devonian Chattanooga Shale in the Dupont GHS drillcore from the western margin of the Nashville Dome, the Upper Devonian Chattanooga Shale comprises several depositional units separated by intraformational hiatuses. These features are developed within a 13.3 m interval consisting of 4.2 m of Frasnian strata and 9.1 m of Famennian strata that unconformably overlie the Sellersburg Formation. Three Frasnian, seven Famennian, and one Tournaisian conodont biozones are recognized. The Frasnian-Famennian boundary is on a disconformity. To the northeast in the southern Illinois Basin, the New Albany Shale in the BCC drillcore consists of 35 m of Givetian and Frasnian strata and 30 m of Famennian strata that conformably overlie the Sellersburg Formation. One Givetian, four Frasnian, and three of the four lowest Famennian conodont zones are recognized. The Frasnian-Famennian boundary is conformable and constrained to within a 5 cm interval. Bulk magnetic susceptibility (MS) shows a long-term increase through most of the Frasnian. Shorter-term MS trends were observed in association with depositional pulses linked to global sea-level rises and highstand system tracts, characterized by total organic carbon (TOC) maxima — eight trends were resolved in the DGHS core, and six in the BCC. The high-frequency shifts in δMS likely represent Milankovitch-band sea-level and depositional cycles at a scale that cannot be resolved based on the condensed and irregular nature of the depositional packages. Gamma ray counts in the DGHS peak in association with the eight depositional cycles, with a TOC peak at the base of each cycle.

A Neognathodus-based biozonation of the Desmoinesian Series (Pennsylvanian) in the Illinois Basin, USA

AbstractThe Neognathodus Index (NI) is developed as a primary biostratigraphic indicator for the Desmoinesian Series of the Illinois Basin in Indiana, Illinois, and Kentucky. It is based on the gradual evolutionary morphotypic variations of P1 elements of named species of Neognathodus Dunn, 1970. The NI analyses and zonations presented herein are constructed from 472 productive conodont samples from 105 different localities. NIs for the Illinois Basin show morphologic drift in Indiana from the Perth Limestone Member of the Staunton Formation (NI = 2.03) to the Velpen Limestone and Mecca Quarry Shale members of the Linton Formation (NI = 5.04) followed by stability through the Alum Cave (NI = 4.83). Further morphologic drift then occurred through the Providence Limestone Member of the Dugger Formation (NI = 5.43) and continued through the West Franklin Limestone Member of the Shelburn Formation (NI = 6.32) until the extinction of Neognathodus at the end of Desmoinesian. The patterns of drift and stability translate to Neognathodus biozones and are supported by Kolmogorov-Smirnov tests of standardized Neognathodus morphotype distributions. Localized NI variations are due to morphologic shifts and differential evolution in response to localized environmental conditions. Examination of the NI differences in the states of Illinois, Kentucky, and Indiana reflect similar morphologic simplification of the P1 element from Perth to Velpen and Mecca Quarry in Indiana (NI = 2.03–5.04) and from Seville to Brereton in Illinois and Kentucky (NI = 2.80–5.00). Post-Brereton in Illinois and Kentucky (NI = 5.00–5.65) and post-Providence in Indiana (NI = 5.43–6.32) saw progressive P1 simplification, but it was much more pronounced in Indiana.

Organic matter content and type variation in the sequence stratigraphic context of the Upper Devonian New Albany Shale, Illinois Basin

Organic matter quantity and type are important parameters in conventional source rock evaluation and unconventional shale oil/gas reservoir characterization. Understanding the stratigraphic distribution of organic matter content and type in black shale successions is critical for identifying potentially productive intervals, because organic matter can adsorb large amounts of oil and gas. Detailed examination of total organic carbon content, organic petrographic composition, and high-resolution (8 cm spacing) geochemical proxies in a sequence stratigraphic framework were conducted on an early mature (0.55% Ro) New Albany Shale core of the Illinois Basin to study the influence of relative sea-level fluctuations on paleoproductivity, clastic supply, bottom-water redox conditions, and their combined control on total organic carbon distribution pattern and organic maceral variation.Marine organic matter including amorphous organic matter and alginite (mainly derived from Tasmanites cysts) is the dominant organic matter in the New Albany Shale. Terrestrial organic matter accounts for <10% of total organic matter. Within a sequence stratigraphic context, total organic carbon content increases in transgressive systems tracts, reaches a maximum before the maximum flooding surface, and shows relatively low values in highstand systems tracts. Comparatively, low total organic carbon contents at maximum flooding surfaces reflect a combination of low sedimentation rates, elevated bottom-water oxygenation, and high biogenic silica dilution.Stratigraphically, amorphous organic matter content increases in transgressive systems tracts, reaches a maximum near the maximum flooding surface, and decreases in highstand systems tracts. Enrichment of broken Tasmanites cysts and their detrital infills are an indicator of high-energy environments and could possibly indicate lowstand systems tracts. The stratigraphic distribution of organic matter content and type may result in cyclic stratigraphic variations of hydrocarbon generation potential and oil saturation, and influence the development of secondary organic pores when the New Albany Shale is within the oil and gas windows.

Evaluation of methane release from coals from the San Juan basin and Powder River basin

To enhance methane release from bituminous coal in the Illinois basin, a nutrient recipe, an adapted microbial community, and optimal biogasification condition leading to maximum methane release have been developed. To evaluate whether the developed strategy is applicable to coals from other geological settings, coal samples from the San Juan (SJ) basin and Powder River (PR) basin were investigated. This study showed that without the addition of ethanol, more methane was released from PR coal than from SJ coal. Ethanol increased and inhibited methane production from SJ and PR coal, respectively. The dominant degradation products in all microcosms were similar even though the concentrations of identified compounds were dependent on the coal samples used. The addition of 2-bromoethanesulfonate completely arrested methanogenesis and resulted in higher content of total organic carbon in fermentation broth than those without. Comparing the coals before and after biotreatment, the elemental compositions did not change much even though significant mass losses were found for both coals. This study demonstrated that a given microbial community can be used for different ranks of coals. To maximize methane release, nutrient recipes may be shared for coals with the same rank, but not for coals having different compositions.

Modeling Commercial-Scale CO2 Injection in Mt. Simon Sandstone Near Decatur, IL Storage Sites

Advancing carbon capture and storage (CCS) to commercialization necessitates exploiting CO2 storage resources efficiently, which likely will involve multiple injection sites (or entire projects) accessing the same regional storage complex. This situation is presently occurring in central Illinois, where a series of three U.S. Department of Energy-sponsored storage projects are utilizing the Cambrian Mt. Simon Sandstone storage complex near Decatur, Illinois. From 2011 to 2014, the Illinois Basin – Decatur Project (IBDP) injected CO2 at a rate of 0.33 million tonnes per year (Mt/yr), and in 2017, the Illinois Industrial CCS Project (IL-ICCS) began injecting approximately 1 Mt/yr (planned rate) in a well 1.6 km apart. Recently, the CarbonSAFE Illinois – Macon County Project began investigating whether more than 50 Mt of CO2 can be injected into the Mt. Simon Sandstone over several decades (a target rate of 2 Mt/yr) located at a site about 5 km northwest of the other injection locations. As evaluated for this study, the Macon County well would be within the Forsyth Oil Field and drilled to access the same interval of the Mt. Simon storage complex as used by the other injection projects, namely the lower Mt Simon Sandstone. The intent of this paper is to assess the feasibility of the Forsyth site for commercial CO2 storage to further develop the storage resource by evaluating whether the target rate can be achieved, designing an injector to meet the target rate, and describing the potential contact of subsurface plumes resulting from these separate but proximal central Illinois projects. This entails modelling the behaviour of the injected CO2 and evaluating the well perforated intervals, plume sizes, pressure responses, and contact with existing CO2 plumes at the Decatur sites. To understand the interaction of three subsurface plumes, a static geologic model was generated to encompass the proposed Forsyth site (CarbonSAFE project) and the existing Decatur sites (IBDP and IL-ICCS projects), an area 22.5  22.5 km2 and a vertical section of 664 m. The static model was developed to represent the geological architecture and heterogeneity of the Mt. Simon storage complex at the Forsyth and Decatur sites through regional correlations based on geophysical data from wells at the Decatur sites. A dynamic model with integrated fluid and rock–fluid properties was constructed from the static model. The primary CO2 storage mechanisms modeled were structural and stratigraphic trapping, residual gas trapping, and solubility trapping. Mineral trapping resulting from geochemical reactions among CO2, rock, and formation water were considered negligible because the target formation is quartz sandstone.