Illinois Basin Research Articles

Significance of analytical particle size in low-pressure N2 and CO2 adsorption of coal and shale

This study examines the influence of analytical particle size on the surface area and mesopore and micropore volume data obtained from low-pressure N2 and CO2 adsorption analyses in response to the crushing of coal and shale. Pennsylvanian high-volatile bituminous coal (Ro~0.57%) and Devonian to Lower Mississippian low-maturity (Ro~0.57%) and high-maturity (Ro~1.30%) shales from the Illinois Basin were progressively crushed from chunks (~7mm) to 4mesh (<4.78mm), 7mesh (<2.83mm), 18mesh (<1mm), 30mesh (0.595mm), 60mesh (<0.250mm), 200mesh (<0.074mm), and 230mesh (<0.063mm), and, subsequently, low-pressure N2 and CO2 adsorption analyses were performed on all the grain size fractions. Our results demonstrate that the values of both surface area and specific mesopore and micropore change with progressive crushing. For example, BET surface area of coal shows a steady increase from 2m2/g in the 4mesh fraction to 4.7m2/g in the 200mesh fraction. For comparable size ranges, BET surface area changes from 0.15 to 7.82m2/g in the low-maturity shale, and from 0.02 to 6.26m2/g in the high-maturity shale. Changes in mesoporosity and microporosity parameters indicate that the coarsest fractions (4mesh and larger) are not suitable for low-pressure adsorption analysis; the values are very low and not reproducible dominantly because of equilibration problems. Our results demonstrate that the 60mesh fraction for coal and the 200mesh fraction for shales seem to be optimal and the most practical sizes for performing low-pressure N2 and CO2 adsorption analysis; these analytical particle sizes yield results closest to the “real” values, unbiased by disequilibrium.

Applications of micro-FTIR technique in studying hydrophobicity of coal

This paper investigates the application of micro-FTIR technique in predicting hydrophobicity of coal inferred from contact angle measurements. Two ranks of coal were selected: Pennsylvanian high-volatile bituminous coal from the Illinois Basin, USA (Ro 0.59–0.63%) and Cretaceous medium-volatile bituminous coal from British Columbia, Canada (Ro 1.19–1.50%). Sessile drop and captive bubble techniques were used to measure contact angle on coal surfaces, and those surfaces were then analyzed with micro-FTIR to correlate contact angle with chemistry. In addition, an image analysis system was used to add the maceral composition effect on chemistry and hydrophobicity. The results show that low- and high-rank coal samples have distinct and opposite trends between functional groups semi-quantitative ratios and contact angle, reflecting rank-dependent effects of chemistry on coal surface hydrophobicity. This work demonstrates that micro-FTIR can be a valuable tool to investigate the hydrophobicity of coal and shows that tracking correlations between chemical groups on the surface of individual macerals, and relating them to hydrophobicity is an effective way to build understanding of the effects of coal chemistry on flotation.

Application of palynology and petrography in the correlation of the Pennsylvanian Brazil and Staunton Formation coals in the eastern part of the Illinois Basin

The coals of the Brazil and the lower part of the Staunton Formations (Atokan and early Desmoinesian, Pennsylvanian) in Indiana (Illinois Basin) are typically thin and discontinuous. As a result, both researchers and the industry have experienced problems with coal bed identification and correlation. The discrepancies in coal nomenclature and frequent miscorrelations affect coal exploration, mine planning, and communication between mines and customers. Our previous study, based on exploration boreholes, mine-scale observations, and coal quality and petrographic data from Daviess, Greene, and Clay Counties, Indiana, suggested that the coal mapped as the Upper Block Coal Member of Clay County might be the same seam as the Lower Block Coal Member of Daviess County. This study is an extension of the previous research conducted farther south to Pike, Warrick, and Spencer Counties, Indiana. In the southern part of Indiana, correlation of these late Atokan and early Desmoinesian coal beds is even more difficult because of the absence of well-defined marker horizons and limited mining and subsurface well data. Although palynological and coal petrography data generally correspond, these data alone cannot resolve the correlation of the coal beds in this southern region with the coals of Clay or Greene Counties, and they must be supplemented with the analysis of associated limestones. The ability to accurately identify the Perth Limestone Member, which occurs close to the Buffaloville Coal Member of the Brazil Formation, and the Holland Limestone Member, which occurs higher up in the Staunton Formation, will help to distinguish between Brazil and Staunton Formation coals.

Active pressure management through brine production for basin-wide deployment of geologic carbon sequestration

In order for carbon capture and storage (CCS) to have a significant impact on anthropogenic carbon emissions, large volumes of carbon dioxide (CO2) will need to be captured and stored in the subsurface. It is therefore likely that multiple storage operations will access the same storage reservoir, leading to the potential for overlapping pressure responses. Pressure management through brine production is an approach to reduce the pressure response of injection operations, concomitantly reducing the potential for overlap. In this study numerical modeling is used to simulate the basin-wide deployment of CCS in the Illinois Basin, USA to determine the potential impact of brine production on pressure increase at the injection wells and the Areas of Review (the area that the US Environmental Protection agency deems at risk for CO2 and brine leakage; AoR) of the injection operations. The results show that brine production can reduce the combined size of AoRs by about one order of magnitude, if a volume of brine equivalent to the volume of injected CO2 is produced. Sites with low injection rates and/or favorable storage properties (i.e., high permeability and porosity, large thickness and depth) may not need pressure management, if the critical pressure is only exceeded within the CO2 plume. Injection of CO2 at locations with favorable storage properties leads to a combined AoR 30% smaller than if the injection sites are co-located with large stationary sources. However, pipeline networks would need to be developed to transport CO2 from the sources to the injection sites. If the produced brine is to be disposed through reinjection into the subsurface, the reinjection formation needs to be hydraulically isolated from the storage formation, as to not negate the effect of pressure management. The results also show that injectivity does not seem to be a major issue in the Illinois Basin, with only four out of 54 hypothetical CCS sites exceeding the allowable pressure increase set to prevent injection-induced seismicity. Unfortunately, brine production is not an effective strategy to control the maximum pressure increase at the four sites, so that a reduction in injection rates is necessary. If the injections occur at locations more favorable for injection, pressures are well below the maximum allowable levels, while maintaining the same basin-wide injection rates.

Influence of varying bedding thickness of underclay on floor stability

The variation in bedding thickness of the weak immediate floor has long been a challenge in the Illinois basin coal mines when it comes to floor stability. The vertical thickness of the immediate floor is not constant throughout the mines and can vary over short horizontal distances. The biggest misconception from a design standpoint is to use the maximum or average thickness found from core logs taken from various locations on the mine property. The result of this practice is oversized pillars in the areas where the weak immediate floor has thinned vertically. This over-design leaves coal in situ which could have otherwise been extracted. This paper presents a plane strain numerical model to illustrate the effect of a change in bedding thickness of a weak immediate floor across one or two coal pillars. The floor bearing capacity of the variable floor below each pillar where then compared to the consistent floor. The results show that the varying bedding thickness of weak underclay has an impact on the bearing capacity of the floor. Geometrically with the decrease in bedding thickness for constant pillar width, the B/H ratio increases exponentially. The influence of varying bedding thickness on the floor bearing capacity is apparent at higher B/H ratios. The floor bearing capacity under a single pillar is in variable floor model if the average thickness remains constant. For single pillar, the average of the bedding thickness can be considered and for pillars in a panel, and a safety factor has been proposed to take into account this change in bedding thickness.

Elucidation of the methanogenic potential from coalbed microbial communities amended with volatile fatty acids.

The potential for modern coalfield methanogenesis was assessed using formation water from the Illinois Basin, Powder River Basin and Cook Inlet gas field as inocula for nutrient-replete incubations amended with C1-C5 fatty acids as presumed intermediates formed during anaerobic coal biodegradation. Instead of the expected rapid mineralization of these substrates, methanogenesis was inordinately slow (∼1 μmol day-1), following long lag periods (>100 days), and methane yields typically did not reach stoichiometrically expected levels. However, a gene microarray confirmed the potential for a wide variety of microbiological functions, including methanogenesis, at all sites. The Cook Inlet incubations produced methane at a relatively rapid rate when amended with butyrate (r = 0.98; p = 0.001) or valerate (r = 0.84; p = 0.04), a result that significantly correlated with the number of positive mcr gene sequence probes from the functional gene microarray and was consistent with the in situ detection of C4-C5 alkanoic acids. This finding highlighted the role of syntrophy for the biodegradation of the softer lignite and subbituminous coal in this formation, but methanogenesis from the harder subbituminous and bituminous coals in the other fields was less apparent. We conclude that coal methanogenesis is probably not limited by the inherent lack of metabolic potential, the presence of alternate electron acceptors or the lack of available nutrients, but more likely restricted by the inherent recalcitrance of the coal itself.

Geologic-carbon-sequestration potential of the Ordovician St. Peter Sandstone, Michigan and Illinois Basins, United States

Cambrian–Ordovician strata of the midwestern United States are considered a promising reservoir for geologic storage of carbon dioxide. To assess the potential of the Ordovician St. Peter Sandstone, storage-resource estimates were generated using a hierarchical approach to estimating prospective storage resources. The method employs a series of increasingly sophisticated analyses to better facilitate an understanding of the uncertainty in the estimates. Results demonstrate how uncertainty of storage-resource estimates varies as a function of data availability and quality as well as the underlying assumptions used in the application of specific storage efficiency factors. In the simplest analysis, storage-resource estimates were calculated from updated regional-scale mapping of the gross thickness of the formation and by applying a single best estimate of the mean porosity for the entire formation. This analysis follows the technique prescribed by the US Department of Energy and yields storage-resource estimates ranging from 3.3 to 35.1 billion t CO2 in the Michigan Basin and 1.0 to 11.0 billion t CO2 in the Illinois Basin at the 10% and 90% probability levels. The second analysis incorporated generalized models of the diagenetic history of the formation throughout the two basins by implementing depth-dependent functions of porosity that lead to more realistic portrayals of spatially variable results. Similar resource estimates were calculated for the Michigan Basin, but reduced estimates (43%) were found for the Illinois Basin. The third analysis explicitly accounted for the local-scale spatial variability in reservoir quality using net-porosity calculations, resulting in a significant increase in the low-range resource estimate for the Michigan Basin and dramatic increases for Illinois Basin resource estimates (factor of 3 to 11 increases). A fourth analysis was conducted for the Michigan Basin that used advanced reservoir characterization to define reservoir properties for multiple reservoir facies and yielded resource estimates significantly larger than the third analysis and a larger range of uncertainty. This study highlights how different factors impact the expected uncertainty in storage-resource estimates, and analysis suggests that estimates from the first two approaches provide excessively conservative results, whereas the second two approaches tend to overestimate the resource.

Carbon isotope analysis of whole-coal and vitrinite from intruded coals from the Illinois Basin: No isotopic evidence for thermogenic methane generation

Igneous intrusions into coals and organic-rich rocks may have contributed to global warming in the geologic past through the release of greenhouse gases. Evidence for a large release of thermogenic CH4 from the organics would include significant δ13Corg enrichment in the residual organic matter (OM). However, δ13Corg values of thermally altered OM in coals and shales adjacent to intrusions often show negative trends or, in some cases, ambiguous or positive trends. Previous studies have evaluated the δ13Corg of whole-coal samples rather than that of individual organic components, or macerals. As different macerals have different isotopic compositions, maceral-specific trends may be masked by variations in maceral composition of the bulk samples. This study evaluates the hypothesis that, if a large-scale release of 13C-depleted thermogenic CH4 resulted from intrusion of the coal, then it should have produced 13C-enriched coal residuum and, specifically, vitrinite (the most abundant component of the coal) adjacent to the intrusion. This study reports geochemical and petrographic data for whole-coal samples and vitrinite macerals (separated via density-gradient centrifugation, DGC) from a transect of thermally altered Springfield (No. 5) Coal (Pennsylvanian) in the Illinois Basin.Approaching the dike contact, mean vitrinite reflectance (Rr) increases from background levels of 0.55% up to ~4.8% and liptinites become indistinguishable from vitrinite. Isotropic and fine-grained circular mosaic coke is observed in samples within ~1.3m of the coal/intrusion contact. Approaching the intrusion, volatile matter (VM) decreases and fixed carbon (FC) and %C increase, whereas %H decreases. Total organic carbon (TOC) for whole coal decreases from 77% to 34%, whereas TOC for separated vitrinite fractions increases from ~66% to 93% toward the coal/intrusion contact. Density of DGC-separated vitrinites ranges from 1.27g/mL in the unaltered coal to 1.52g/mL in the sample adjacent to the coal/intrusion contact. Vitrinite density increases with increased Rr and %C, and decreases with increased %H and H/C.Despite these marked geochemical and petrographic changes, no significant changes in δ13Corg values of the whole coal (−25.3‰ to −24.9‰) or the separated vitrinites (−25.3‰ to −25.0‰) occur proximal to the intrusion. Changes in the isotopic signatures are not of a magnitude that would be expected if significant quantities of isotopically depleted thermogenic CH4 had been generated by the intrusive event. Moreover, no petrographic evidence supports the occurrence of condensed or immobilized thermal products due to rapid pyrolysis (such as 12C-rich pyrolytic carbon) close to the intrusion that could have moderated any changes in δ13Corg. Geochemical and petrographic results suggest that only minimal loss of CH4 was associated with the rapid heating of the Springfield (No. 5) Coal by the intrusion. These findings have significant implications for models linking past global warming to the intrusion of coals and carbonaceous shales.

Maceral controls on porosity characteristics of lithotypes of Pennsylvanian high volatile bituminous coal: Example from the Illinois Basin

Porosity characteristics of vitrain, clarain, durain, and fusain lithotypes of the Springfield Coal Member of the Petersburg Formation and the Danville and Hymera Coal Members of the Dugger Formation from the Illinois Basin were investigated with a special emphasis on the control of coal macerals on pore-size distribution. These Pennsylvanian coals are of high volatile bituminous rank and have vitrinite reflectance ranging from 0.51 to 0.60%. The lithotypes studied show decreasing values of Brunauer-Emmett-Teller surface area, and micro- and mesopore volumes from vitrain through clarain and durain to fusain. Within the mesopore size range, vitrain and clarain are dominated by pore-size widths of 4 to 10nm, whereas durain and fusain have more volume for pores larger than 20nm. In contrast to mesopores, micropore sizes are very similar for all lithotypes, averaging 1.37 to 1.39nm. In addition to differences among lithotypes, there are significant differences in pore characteristics among the three coals studied, with largest surface areas and pore volumes documented for the Hymera, followed by the Danville and the Springfield. A strong relationship exists between surface area, mesoporosity, and microporosity and maceral composition, with vitrinite having a very strong positive correlation, liptinite having a weak positive correlation, and inertinite having a strong negative correlation. Negative correlations of total porosity with vitrinite and liptinite and positive correlations with inertinite suggest that among the maceral groups, pores in inertinite contribute most to the total porosity. The Fourier transform infrared spectrometry technique demonstrates that fusains from the three coals studied have higher aromaticity and a higher degree of aromatic ring condensation and lower hydrocarbon potential than the other lithotypes, whereas chemical differences between vitrain, clarain, and durain are less distinct. In addition, there is a relationship between aromaticity of the lithotypes and surface area and mesopore and micropore volumes.

In situ δ13C and δ18O microanalysis by SIMS: A method for characterizing the carbonate components of natural and engineered CO2-reservoirs

This work addresses the potential utility of in situ carbon and oxygen isotope microanalysis (δ13C and δ18O) by secondary ion mass spectrometry (SIMS) in carbon sequestration research. A desirable long-term consequence of CO2-injection into underground rock formations at prospective sequestration sites (such as deep saline sandstone aquifers capped by impermeable strata) is the precipitation of carbonate mineral cements, the isotopic fingerprinting of which is a central theme here. More specifically, we focus on the unique advantage of the SIMS technique, which lies in the capability of analyzing very small sample volumes that are otherwise inaccessible to sampling techniques in conventional isotope ratio mass spectrometry (IRMS). For example, single carbonate crystallites as small as 3–10μm across can be readily analyzed by SIMS with sub per-mil (‰) accuracy and precision. Importantly, the ability to perform micrometer-scale measurements in situ from either thin sections or 1-in. (25mm) diameter polished core plugs preserves the petrographic context of measured carbonate δ18O and δ13C values.We provide a preliminary characterization of the pre-injection mineralogy and isotopic fingerprints of carbonate cements in the Mount Simon Sandstone reservoir and the overlying silty-shaly caprock (the Eau Claire Formation) at the Illinois Basin Decatur Project, a demonstration and research site for exploring the feasibility of long-term CO2 storage in a deep saline aquifer. By drawing upon published data on ambient reservoir conditions and the isotopic composition of the injected CO2, we make simple predictions regarding possible δ13C values of calcite, dolomite-ankerite, and siderite cements that may form in response to long-term CO2 storage.

Three-dimensional modeling of Pennsylvanian sandstone units in the mature Dudley oil field, Illinois, USA

The purpose of this research is to better understand the Dudley Pool, a small, mature oil field in the Illinois Basin, USA by incorporating old geologic and geophysical data into modern petrophysical modeling software. The research focused on three-dimensional subsurface modeling of stratigraphy, structure, and porosity, to establish a more thorough understanding of oil occurrence at the Dudley Pool. This research also discusses the efficacy of three-dimensional modeling as an effective tool for evaluating, and potentially modifying, production efforts in mature petroleum fields with limited and/or poor-quality data. The modeling and calculations were completed using Petrel. Well information from all wells drilled within a one mile collar of the field was collected. The model generated contour maps, thickness maps, a facies model, cross sections, core logging and a porosity model. The project established that the Dudley Pool is part of a major channel system heading southeast toward the interior of the Illinois Basin and, thus, may present additional resources for exploitation beyond the current production limit of the field. Isopach and structure contour trends indicate that areas to the northeast are targets for future exploration and development of the Dudley Pool.

Depositional and diagenetic controls on anomalously high porosity within a deeply buried CO2 storage reservoir—The Cambrian Mt. Simon Sandstone, Illinois Basin, USA

Current diagenetic models predict that sandstone porosity and reservoir quality decrease with burial depth and formation age. However, the opposite trend is true for the Cambrian Mt. Simon Sandstone. The lowermost section of the Mt. Simon is highly porous—it has an average log-derived effective porosity of 17.0%. To understand the possible reason(s) for this anomaly, the amount of porosity reduction due to compaction porosity loss (COPL) and cementation porosity loss (CEPL) was analyzed. The COPL and CEPL were coupled with sedimentary characteristics in order to ascertain which factors controlled porosity and reservoir quality in the Mt. Simon. The underlying Argenta sedimentary unit disconformably underlies the Mt. Simon and is included for diagenetic and depositional comparison.Similar to expected trends from other deep basin reservoirs, the COPL generally increases with depth in the Mt. Simon. The CEPL is significantly lower in the lower half of the Mt. Simon compared to the upper half of the Mt. Simon, indicating that higher porosity is attributed to having a lower volume of intergranular cement. Early episodes of diagenesis within the arkosic lower half of the Mt. Simon, such as clay infiltration and feldspar alteration, produced diagenetic grain-coating clays, which inhibited the development of quartz cements. Thus, these grain coatings assisted in porosity preservation within the Lower Mt. Simon by reducing CEPL. The upper half of the Mt. Simon is more heavily cemented as a result of changes in the depositional setting and thus changes in the lithology. Later, largely post-compaction feldspar dissolution further increased porosity in the Lower Mt. Simon Sandstone.

Coal depolymerization using permanganate under optimal conditions

For the purpose of solubilizing coal for liberating valuable chemicals, permanganate was used as an oxidant. To obtain the highest yield of soluble compounds from coal, permanganate was studied at different concentrations and different temperatures with different loading of bituminous coal from the Illinois basin. The optimal condition for dissolving 60% of the bituminous coal was: KMnO4 at 0.45mol/L; temperature at 25°C; coal loading at 50g/L in a tumbler set at 45rpm for 21days. A mathematical equation was developed for predicting yield of soluble compounds from coal based on experimental data. Upon verifying the results predicted by the model, coal treatment also included samples from the San Juan basin and the Powder River Basin. After treatment, the residual coal was characterized in terms of elemental composition. The aqueous phase was subjected to analysis of total organic carbon (TOC), volatile compounds by HPLC and dichloromethane solubles by GC–MS. Considering the high TOC content demonstrated from this study, this work provided a cost-effective way for obtaining value-added chemicals from coal at different locations.

Conodont (U–Th)/He thermochronology: A case study from the Illinois Basin

Acquisition of thermochronologic data in carbonates and shales has traditionally been elusive owing to the paucity of dateable minerals in these lithologies. Conodont apatite (U–Th)/He (CAHe) thermochronology has the potential to fill this need. We acquired 50 (U–Th)/He dates for conodonts with CAI values ≤1.5 from seven Pennsylvanian shale and limestone samples from two drillcores in the Illinois Basin. We also obtained X-Ray microcomputed tomography (MicroCT) results for 8 conodonts to evaluate the accuracy of alpha-ejection corrections. The simplified geometric corrections yield corrected dates within 5% of those derived from 3D characterization using MicroCT. Nearly all of the conodont CAHe dates are substantially younger than their depositional age, indicating that maximum post-depositional temperatures of ≤90 °C caused He loss over geologic timescales. The youngest and most reproducible dates consist of whole platform elements from shales, and may record a regional Late Cretaceous–early Tertiary cooling and erosion event. The remainder of the data exhibit strong negative date-U and date-Th correlations, characterized by higher and more variable Th/U than the conodonts with reproducible dates. These patterns are best explained by U loss, with more limited Th loss. The results suggest that whole platform elements and higher U–Th conodont materials are the most promising targets for CAHe analysis.

Microseismicity of the Intraplate Northern Wabash Fault System and La Salle Anticlinorium, Illinois Basin, U.S.A.

ABSTRACT Within the Illinois basin, the northern Wabash Valley seismic zone (WVSZ) and adjoining La Salle anticlinal belt have produced three moderate‐sized earthquakes ranging from m b 4.7 to m b 5.2 in the past 50 years. However, few smaller events from this area are recorded in regional catalogs. The Wabash fault system extends from the junction of the Rough Creek and Cottage Grove faults in the south along the Wabash River into the La Salle anticlinal belt to the north. These faults extend through the Paleozoic and into the Precambrian basement. Two of these moderate‐sized earthquakes occurred north of the terminus of the Wabash Valley fault system where it meets the La Salle anticline. The La Salle anticline, a Precambrian basement feature, is oriented northwest to southeast. The La Salle anticline creates up to a 750 m uplift in the above Paleozoic strata. This uplift creates faults within the Paleozoic strata and within the La Salle anticline. This study uses a nine‐seismograph phased array near the southern terminus of the La Salle anticline to monitor the microseismicity of the region. Analyzing the seismicity of the region over a six‐month period found 834 events. The vast majority were determined to be mine blasts or otherwise human induced. Two small earthquakes ( M L ∼1.0) located near the La Salle anticline. These earthquakes likely occur on faults associated with the anticline. The lack of microearthquakes suggests the b ‐value of the La Salle region is lower than the typical value of 1. The b ‐value is consistent with other intraplate regions and previous studies of the WVSZ finding values nearer 0.7 or even potentially as low as 0.6.

Applicability of micro-FTIR in detecting shale heterogeneity.

Samples of Late Devonian/Early Mississippian New Albany Shale from the Illinois Basin, having maturities ranging from early mature to postmature, were analysed using micro-Fourier transform infrared (FTIR) spectroscopy, ImageJ processing software and scanning electron microscopic X-ray spectroscopy to explore the distribution, connectivity and chemical composition of organic matter, clay minerals, carbonate minerals and quartz, and to further test the applicability of micro-FTIR mapping to study shale heterogeneity. Each sample was analysed in planes parallel and perpendicular to the bedding to investigate anisotropy in component distribution, with a possible implication for better understanding anisotropy in porosity and permeability in organic-matter-rich shales. Our results show that for low-maturity samples, organic matter is better connected in the plane parallel to the bedding than in the plane perpendicular to the bedding. Organic matter connectivity decreases with increasing maturity as a result of kerogen transformation. Clay minerals are very well connected in both planes, whereas carbonate minerals are not abundant whilst dominantly isolated in most samples, independent of maturity. This study demonstrates that micro-FTIR mapping is a valuable tool for studying shale heterogeneity on a micrometre to millimetre scale that becomes even more powerful in combination with scanning electron microscopy techniques, which extend observations to a nanometre scale. However, to obtain meaningful and comparable results, micro-FTIR mapping requires very careful standardization, precise selection of peak heights/areas and mapping conditions (such as aperture size, scan numbers, resolution, etc.) well suited for the analysed samples.

Optimization of methane production from bituminous coal through biogasification

To optimize methane production from bituminous coal through use of a well-studied microbial community derived from the same Illinois basin in USA, a total of 12 parameters were first evaluated by setting up 64 reactors following a 2-level factorial design. Among the 12 parameters, temperature, coal loading, particle size and ethanol were found to have statistically significant effects on methane content and yield from coal. Following screening, to identify optimal value for each significant factor, a Box-Behnken design necessitating 29 reactors was adopted. Optimal conditions provided by the Design of Expert software for the highest methane yield were: temperature, 32°C; coal loading, 201.98g/L; coal particle size, <73.99μm; and ethanol at 300mM. Under these optimum conditions, the predicted methane yield and content was 2957.4ft3/ton (83.7mm3/ton) and 74.2%, respectively. To confirm the predicted results, a verification experiment was conducted, where a methane yield of 2900ft3/ton (82.1mm3/ton) with a methane content of 70% was observed. Thus, models developed from this study can be used to predict methane content and yield from bituminous coal through biogasification ex situ.

LesleyaLesquereux from the Pennsylvanian of the Iberian Massif: part of a dryland megaflora from the Variscan orogen, northwestern Portugal

The Carboniferous – early Permian plant genus Lesleya is a characteristic component of “dryland floras” that occupied a wide range of moisture-stressed, well-drained environments in tropical regions of Euramerica. Fossil records of Lesleya are almost exclusively found in basinal lowlands. For example, occurrences in Early Pennsylvanian-age, seasonally dry, parautochthonous deposits in basinal lowlands of North America (e.g., Illinois Basin, USA) indicate that Lesleya lived in that region in low-altitude (lowland) paleoenvironments during dry climatic intervals. In this paper, we document the first occurrence of Lesleya during the Carboniferous on the Iberian Massif, in lower Gzhelian (Upper Pennsylvanian) strata of the Douro Carboniferous Basin, in northwestern Portugal. This newly discovered occurrence includes a new species, Lesleya iberiensis sp. nov., recognized on the basis of natural molds of leaves. The Portuguese Lesleya fossils are from upland intramontane deposits and occur between coal beds. Their fossil remains are preserved in mica-rich shales that were deposited between sandstone-dominated fluvial and shale-dominated lacustrine deposits, suggesting that this megaflora was deposited near freshwater bodies. These new data provide evidence that this megaflora grew in mountain riparian environments within the Variscan orogen, either in localized, well-drained areas or during drier climatic intervals in the Late Pennsylvanian.

Dryland vegetation from the Middle Pennsylvanian of Indiana (Illinois Basin): the dryland biome in glacioeustatic, paleobiogeographic, and paleoecologic context

AbstractA macrofloral assemblage dominated by elements of the Euramerican dryland biome is described from the Brazil Formation in Clay County, Indiana (Illinois Basin). Fossils were recovered from a thin heterolithic unit between a shallow-marine bed and the paleosol beneath the Minshall Coal, a Middle Pennsylvanian succession deposited near the Atokan-Desmoinesian and Bolsovian-Asturian boundaries. Sedimentological indicators imply accumulation under a seasonal climate, including interbedded siltstone and sandstone deposited during flashfloods, intraclasts eroded from local sources, and charcoal produced by wildfires. The macrofloral assemblage is consistent with a dryland setting, being dominated by large, coriaceous gymnosperm leaves with mesic to xeric traits, includingCordaitesspp. indet.,Lesleyasp. indet., andTaeniopterissp. cf.T. multinervia. Sphenopsids and ferns typical of the wetland biome are rare. In contrast, the microfloral assemblage is dominated by fern spores, with lesser lycopsid spores and cordaitalean pollen. The succession indicates that the dryland biome predominated during late regression, prior to the onset of perhumid conditions that resulted in peat accumulation at late lowstand. However, the abundance of palynomorphs from wetland vegetation implies gradual fragmentation of the prevailing dryland flora and replacement by the wetland biome in the transition to glacial maximum. The taphonomic and paleobiogeographic context confirms that floras adapted to seasonal moisture deficit periodically dispersed into tropical lowlands, rather than being transported from ‘extrabasinal’ or ‘upland’ environments. The precocious occurrence ofTaeniopteris, more typical of Late Pennsylvanian and Permian floras, may be the earliest record of the fossil-genus, and exemplifies the association of derived plant taxa with dryland habitats. The predominance of broad-leaved gymnosperms with mesic to xeric characters suggests that dryland communities contained more slow-growing and long-lived plants than contemporaneous wetland floras.

Orenia metallireducens sp. nov. Strain Z6, a Novel Metal-Reducing Member of the Phylum Firmicutes from the Deep Subsurface.

A novel iron-reducing species, Orenia metallireducens sp. nov., strain Z6, was isolated from groundwater collected from a geological formation located 2.02 km below land surface in the Illinois Basin, USA. Phylogenetic, physiologic, and genomic analyses of strain Z6 found it to have unique properties for iron reducers, including (i) active microbial iron-reducing capacity under broad ranges of temperatures (20 to 60°C), pHs (6 to 9.6), and salinities (0.4 to 3.5 M NaCl), (ii) lack of c-type cytochromes typically affiliated with iron reduction in Geobacter and Shewanella species, and (iii) being the only member of the Halanaerobiales capable of reducing crystalline goethite and hematite. This study expands the scope of phylogenetic affiliations, metabolic capacities, and catalytic mechanisms for iron-reducing microbes.