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USGS2014

Relationships between water and gas chemistry in mature coalbed methane reservoirs of the Black Warrior Basin

Water and gas chemistry in coalbed methane reservoirs of the Black Warrior Basin reflects a complex interplay among burial processes, basin hydrodynamics, thermogenesis, and late-stage microbial methanogenesis. These factors are all important considerations for developing production and water management strategies. Produced water ranges from nearly potable sodium-bicarbonate water to hypersaline sodium-chloride brine. The hydrodynamic framework of the basin is dominated by structurally controlled fresh-water plumes that formed by meteoric recharge along the southeastern margin of the basin. The produced water contains significant quantities of hydrocarbons and nitrogen compounds, and the produced gas appears to be of mixed thermogenic-biogenic origin. Late-stage microbial methanogenesis began following unroofing of the basin, and stable isotopes in the produced gas and in mineral cements indicate that late-stage methanogenesis occurred along a CO 2 -reduction metabolic pathway. Hydrocarbons, as well as small amounts of nitrate in the formation water, probably helped nourish the microbial consortia, which were apparently active in fresh to hypersaline water. The produced water contains NH 4 + and NH 3 , which correlate strongly with brine concentration and are interpreted to be derived from silicate minerals. Denitrification reactions may have generated some N 2 , which is the only major impurity in the coalbed gas. Carbon dioxide is a minor component of the produced gas, but significant quantities are dissolved in the formation water. Degradation of organic compounds, augmented by deionization of NH 4 + , may have been the principal sources of hydrogen facilitating late-stage CO 2 reduction.

Alabama↗

USGS2014

Surface disposal of produced waters in western and southwestern Pennsylvania: potential for accumulation of alkali-earth elements in sediments

Waters co-produced with hydrocarbons in the Appalachian Basin are of notably poor quality (concentrations of total dissolved solids (TDS) and total radium up to and exceeding 300,000 mg/L and 10,000 pCi/L, respectively). Since 2008, a rapid increase in Marcellus Shale gas production has led to a commensurate rise in associated wastewater while generation of produced water from conventional oil and gas activities has continued. In this study, we assess whether disposal practices from treatment of produced waters from both shale gas and conventional operations in Pennsylvania could result in the accumulation of associated alkali earth elements. The results from our 5 study sites indicate that there was no increase in concentrations of total Ra (Ra-226) and extractable Ba, Ca, Na, or Sr in fluvial sediments downstream of the discharge outfalls (p > 0.05) of publicly owned treatment works (POTWs) and centralized waste treatment facilities (CWTs). However, the use of road spreading of brines from conventional oil and gas wells for deicing resulted in accumulation of Ra-226 (1.2 ×), and extractable Sr (3.0 ×), Ca (5.3 ×), and Na (6.2 ×) in soil and sediment proximal to roads (p < 0.05). Although this study is an important initial assessment of the impacts of these disposal practices, more work is needed to consider the environmental consequences of produced waters management.

Pennsylvania↗

USGS2014

A review of environmental impacts of salts from produced waters on aquatic resources

Salts are frequently a major constituent of waste waters produced during oil and gas production. These produced waters or brines must be treated and/or disposed and provide a daily challenge for operators and resource managers. Some elements of salts are regulated with water quality criteria established for the protection of aquatic wildlife, e.g. chloride (Cl − ), which has an acute standard of 860 mg/L and a chronic standard of 230 mg/L. However, data for establishing such standards has only recently been studied for other components of produced water, such as bicarbonate (HCO 3 − ), which has acute median lethal concentrations (LC50s) ranging from 699 to > 8000 mg/L and effects on chronic toxicity from 430 to 657 mg/L. While Cl− is an ion of considerable importance in multiple geographical regions, knowledge about the effects of hardness (calcium and magnesium) on its toxicity and about mechanisms of toxicity is not well understood. A multiple-approach design that combines studies of both individuals and populations, conducted both in the laboratory and the field, was used to study toxic effects of bicarbonate (as NaHCO 3 ). This approach allowed interpretations about mechanisms related to growth effects at the individual level that could affect populations in the wild. However, additional mechanistic data for HCO 3 − , related to the interactions of calcium (Ca 2 + ) precipitation at the microenvironment of the gill would dramatically increase the scientific knowledge base about how NaHCO 3 might affect aquatic life. Studies of the effects of mixtures of multiple salts present in produced waters and more chronic effect studies would give a better picture of the overall potential toxicity of these ions. Organic constituents in hydraulic fracturing fluids, flowback waters, etc. are a concern because of their carcinogenic properties and this paper is not meant to minimize the importance of maintaining vigilance with respect to potential organic contamination.

International Journal of Coal Geology↗

USGS2014

Organic substances in produced and formation water from unconventional natural gas extraction in coal and shale

Organic substances in produced and formation water from coalbed methane (CBM) and gas shale plays from across the USA were examined in this study. Disposal of produced waters from gas extraction in coal and shale is an important environmental issue because of the large volumes of water involved and the variable quality of this water. Organic substances in produced water may be environmentally relevant as pollutants, but have been little studied. Results from five CBM plays and two gas shale plays (including the Marcellus Shale) show a myriad of organic chemicals present in the produced and formation water. Organic compound classes present in produced and formation water in CBM plays include: polycyclic aromatic hydrocarbons (PAHs), heterocyclic compounds, alkyl phenols, aromatic amines, alkyl aromatics (alkyl benzenes, alkyl biphenyls), long-chain fatty acids, and aliphatic hydrocarbons. Concentrations of individual compounds range from < 1 to 100 μg/L, but total PAHs (the dominant compound class for most CBM samples) range from 50 to 100 μg/L. Total dissolved organic carbon (TOC) in CBM produced water is generally in the 1–4 mg/L range. Excursions from this general pattern in produced waters from individual wells arise from contaminants introduced by production activities (oils, grease, adhesives, etc.). Organic substances in produced and formation water from gas shale unimpacted by production chemicals have a similar range of compound classes as CBM produced water, and TOC levels of about 8 mg/L. However, produced water from the Marcellus Shale using hydraulic fracturing has TOC levels as high as 5500 mg/L and a range of added organic chemicals including, solvents, biocides, scale inhibitors, and other organic chemicals at levels of 1000 s of μg/L for individual compounds. Levels of these hydraulic fracturing chemicals and TOC decrease rapidly over the first 20 days of water recovery and some level of residual organic contaminants remain up to 250 days after hydraulic fracturing. Although the environmental impacts of the organics in produced water are not well defined, results suggest that care should be exercised in the disposal and release of produced waters containing these organic substances into the environment because of the potential toxicity of many of these substances.

International Journal of Coal Geology↗

USGS2015

Microscopical characterization of carbon materials derived from coal and petroleum and their interaction phenomena in making steel electrodes, anodes and cathode blocks for the Microscopy of Carbon Materials Working Group of the ICCP

This paper describes the evaluation of petrographic textures representing the structural organization of the organic matter derived from coal and petroleum and their interaction phenomena in the making of steel electrodes, anodes and cathode blocks. This work represents the results of the Microscopy of Carbon Materials Working Group in Commission III of the International Committee for Coal and Organic Petrology between the years 2009 and 2013. The round robin exercises were run on photomicrograph samples. For textural characterization of carbon materials the existing ASTM classification system for metallurgical coke was applied. These round robin exercises involved 15 active participants from 12 laboratories who were asked to assess the coal and petroleum based carbons and to identify the morphological differences, as optical texture (isotropic/anisotropic), optical type (punctiform, mosaic, fibre, ribbon, domain), and size. Four sets of digital black and white microphotographs comprising 151 photos containing 372 fields of different types of organic matter were examined. Based on the unique ability of carbon to form a wide range of textures, the results showed an increased number of carbon occurrences which have crucial role in the chosen industrial applications. The statistical method used to evaluate the results was based on the “raw agreement indices”. It gave a new and original view on the analysts' opinion by not only counting the correct answers, but also all of the knowledge and experience of the participants. Comparative analyses of the average values of the level of overall agreement performed by each analyst in the exercises during 2009–2013 showed a great homogeneity in the results, the mean value being 90.36%, with a minimum value of 83% and a maximum value of 95%.

International Journal of Coal Geology↗

USGS2015

Re–Os age for the Lower–Middle Pennsylvanian Boundary and comparison with associated palynoflora

The Betsie Shale Member is a relatively thick and continuous unit that serves as a marker bed across the central Appalachian basin, in part because it includes an organic-rich shale unit at its base that is observable in drill logs. Deposited during a marine transgression, the Betsie Shale Member has been correlated to units in both Wales and Germany and has been proposed to mark the boundary between the Lower and Middle Pennsylvanian Series within North America. This investigation assigns a new Re–Os date to the base of the Betsie and examines the palynoflora and maceral composition of the underlying Matewan coal bed in the context of that date. The Matewan coal bed contains abundant lycopsid tree spores along its base with assemblage diversity and inertinite content increasing upsection, as sulfur content and ash yield decrease. Taken together, these palynologic and organic petrographic results suggest a submerged paleomire that transitioned to an exposed peat surface. Notably, separating the lower and upper benches of the Matewan is a parting with very high sulfur content (28 wt.%), perhaps representing an early marine pulse prior to the full on transgression responsible for depositing the Betsie. Results from Re–Os geochronology date the base of the Betsie at 323 ± 7.8 Ma, consistent with previously determined age constraints as well as the palynoflora assemblage presented herein. The Betsie Shale Member is also highly enriched in Re (ranging from 319.7 to 1213 ng/g), with high 187 Re/ 188 Os values ranging from 3644 to 5737 likely resultant from varying redox conditions between the pore water and overlying water column during deposition and early condensing of the section.

West Virginia↗

USGS2015

Enhanced microbial coalbed methane generation: A review of research, commercial activity, and remaining challenges

Coalbed methane (CBM) makes up a significant portion of the world’s natural gas resources. The discovery that approximately 20% of natural gas is microbial in origin has led to interest in microbially enhanced CBM (MECoM), which involves stimulating microorganisms to produce additional CBM from existing production wells. This paper reviews current laboratory and field research on understanding processes and reservoir conditions which are essential for microbial CBM generation, the progress of efforts to stimulate microbial methane generation in coal beds, and key remaining knowledge gaps. Research has been primarily focused on identifying microbial communities present in areas of CBM generation and attempting to determine their function, in-situ reservoir conditions that are most favorable for microbial CBM generation, and geochemical indicators of metabolic pathways of methanogenesis (i.e., acetoclastic or hydrogenotrophic methanogenesis). Meanwhile, researchers at universities, government agencies, and companies have focused on four primary MECoM strategies: 1) microbial stimulation (i.e., addition of nutrients to stimulate native microbes); 2) microbial augmentation (i.e., addition of microbes not native to or abundant in the reservoir of interest); 3) physically increasing microbial access to coal and distribution of amendments; and 4) chemically increasing the bioavailability of coal organics. Most companies interested in MECoM have pursued microbial stimulation: Luca Technologies, Inc., successfully completed a pilot scale field test of their stimulation strategy, while two others, Ciris Energy and Next Fuel, Inc., have undertaken smaller scale field tests. Several key knowledge gaps remain that need to be addressed before MECoM strategies can be implemented commercially. Little is known about the bacterial community responsible for coal biodegradation and how these microorganisms may be stimulated to enhance microbial methanogenesis. In addition, research is needed to understand what fraction of coal is available for biodegradation, and methods need to be developed to determine the extent of in-situ coal biodegradation by MECoM processes for monitoring changes to coal quality. Questions also remain about how well field-scale pilot tests will scale to commercial production, how often amendments will need to be added to maintain new methane generation, and how well MECoM strategies transfer between coal basins with different formation water geochemistries and coal ranks. Addressing these knowledge gaps will be key in determining the feasibility and commercial viability of MECoM technology.

International Journal of Coal Geology↗

USGS2015

Mapping of coal quality using stochastic simulation and isometric logratio transformation with an application to a Texas lignite

Coal is a chemically complex commodity that often contains most of the natural elements in the periodic table. Coal constituents are conventionally grouped into four components (proximate analysis): fixed carbon, ash, inherent moisture, and volatile matter. These four parts, customarily measured as weight losses and expressed as percentages, share all properties and statistical challenges of compositional data. Consequently, adequate modeling should be done in terms of a logratio transformation, a requirement that is commonly overlooked by modelers. The transformation of choice is the isometric logratio transformation because of its geometrical and statistical advantages. The modeling is done through a series of realizations prepared by applying sequential simulation for the purpose of displaying the parts in maps incorporating uncertainty. The approach makes realistic assumptions and the results honor the data and basic considerations, such as percentages between 0 and 100, all four parts adding to 100% at any location in the study area, and a style of spatial fluctuation in the realizations equal to that of the data. The realizations are used to prepare different results, including probability distributions across a deposit, E-type maps displaying average properties, and probability maps summarizing joint fluctuations of several parts. Application of these maps to a lignite bed clearly delineates the deposit boundary, reveals a channel cutting across, and shows that the most favorable coal quality is to the north and deteriorates toward the southeast.

International Journal of Coal Geology↗

USGS2017

Mercury and trace element distribution in density separates of a South African Highveld (#4) coal: Implications for mercury reduction and preparation of export coal

Eight density separates of Permian Highveld (#4) coal were investigated for partitioning of Hg and trace elements. The separates include float fractions obtained in heavy media having densities of 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, and 2.0 g/cm 3 , and the sink fraction for 2.0 g/cm 3 . Bulk analysis of the separates shows strong (R 2 ≥ 0.80) positive correlations between pyritic sulfur and mercury, and between ash yield and both pyritic sulfur and mercury. Laser ablation (LA) ICP-MS analysis of individual pyrite grains in the separates confirms association of Hg and As with pyrite as indicated by bulk analysis. Other elements detected in pyrite by LA-ICP-MS include Mn, Co, Ni, Tl, and Pb. Results for the separates allow prediction of Hg, trace elements, and ash yields expected in specific South African coal products. These range from 0.06 ppm Hg and an ash yield of 11.5% ash for the export fraction to 0.47 ppm Hg and an ash yield of 60.9% for the discard (stone) fraction (dry basis). Results show pronounced differences expected between coal used for domestic power generation and coal which is exported.

International Journal of Coal Geology↗

USGS2016

Notes on the origin of copromacrinite based on nitrogen functionalities and δ13C and δ15N determined on samples from the Peach Orchard coal bed, southern Magoffin County, Kentucky

This paper represents the first attempt to show, by means other than just petrographic ones, that one type of macrinite, herein designated copromacrinite, may result from macrofauna feces. For that purpose a combination of coal petrography, X-ray photoelectron spectroscopy, and elemental-analysis continuous-flow isotope ratio mass spectrometry methods were used to determine nitrogen functionalities and δ 13 C and δ 15 N compositions in 1) vitrinite-rich, 2) fusinite + semifusinite-rich, and 3) macrinite-rich (with a possible coprolitic origin) samples of the high volatile A bituminous Peach Orchard coal (Bolsovian; Middle Pennsylvanian) from Magoffin County, Kentucky. There were no significant differences between pyridinic-N and quaternary-N abundance in the three samples, however, pyrrolic-N was higher (~ 54%) in the macrinite-rich sample than in the other two samples (~ 38%). The data suggest that pyridinic-N and quaternary-N are independent of maceral group composition and that pyrrolic-N is dependent on maceral composition (fusinite + semifusinite versus macrinite). δ 13 C values obtained for bulk and demineralized coal of the vitrinite- and fusinite + semifusinite-rich samples are similar with δ 13 C values of − 24.80 ± 0.01&permil; VPDB and − 24.61 ± 0.09&permil; VPDB for bulk samples and − 24.81 ± 0.07&permil; VPDB and − 24.52 ± 0.04&permil; VPDB for demineralized samples. These values are within the expected range for vitrinite-rich samples and the slightly higher δ 13 C value of the fusinite + semifusinite-rich sample is expected as δ 13 C values for inertinite are higher than for vitrinite. However, there was a significant shift to a lower δ 13 C value (− 26.80 ± 0.01&permil; VPDB for the bulk sample value) for the macrinite-rich sample. Because the samples are basically isorank, and δ 13 C (and δ 15 N) shifts do not occur during maturation until anthracite rank, the difference may be related to the presence or composition of the macrinite within the sample which lacks heat-effect indicators, such as devolatilization vacuoles and distorted pores. δ 15 N values are also similar for bulk and demineralized coal of the vitrinite- and fusinite + semifusinite-rich samples, and the bulk values were heavier in this samples (3.07 ± 0.03&permil; Air and 2.92 ± 0.10&permil; Air, respectively), and much lighter (− 2.83 ± 0.09&permil; Air) for the macrinite-rich sample. The study of Peach Orchard coal samples using reflected-light microscopy, isotopic composition, and nitrogen-forms analyses revealed that the macrinite-rich sample contains macrinite with coprolitic features (e.g. oxidation rind, mix of undigested palynomorphs, frequent and randomly located funginite, agglutination pulp of semifusinite reflectance, internal lack of bedding fabric, and suggestion of structures resulting from intestines and stomach walls), more pyrrolic-N (~ 16%), and lower δ 13 C (~ 2&permil; VPDB) and δ 15 N (~ 4&permil; Air) values than the vitrinite and semifusinite + fusinite rich samples. These findings suggest that the maceral macrinite has multiple origins based on petrography and measurable chemical differences between the macrinite, vitrinite, and semifusinite + fusinite fractions within the coal. Assuming that copromacrinite observed is an excretion then the anomalies observed may result from the symbiotic relations between the macrofauna (e.g. cockroaches) and microbiota during the digestive processes, and the nitrogen balance mechanisms inside macrofauna body.

Kentucky↗

USGS2016

Calorific value and compositional ultimate analysis with a case study of a Texas lignite

Measurements to determine coal quality as fuel include proximate analysis, ultimate analysis and calorific value. The latter is an attribute taking non-negative real values, so a simple transformation is sufficient for its spatial modeling applying geostatistics. The analyses, however, involve proportions that follow the properties of compositional data, thus requiring special preprocessing for an adequate modeling already described in a previous publication for the case of proximate analysis data. 1 Here we model the results of calorific value and ultimate analysis. We propose to use two different binary partitions, one per analysis, map the corresponding isometric logratio transformations, and backtransform the results. The methodology is illustrated using the same coal bed in the previous paper modeling proximate analysis data. Results are summarized using probability maps that, in the case of this deposit, show a prominent channel crossing the deposit and separating the best quality coal from that of lower quality.

International Journal of Coal Geology↗

USGS2016

Organic petrology and geochemistry of mudrocks from the lacustrine Lucaogou Formation, Santanghu Basin, northwest China: Application to lake basin evolution

Exploration for tight oil in the frontier Santanghu Basin of northwest China has resulted in recent commercial discoveries sourced from the lacustrine Upper Permian Lucaogou Formation, already considered a “world class source rock” in the Junggar Basin to the west. Here we apply an integrated analytical program to carbonate-dominated mudrocks from the Lucaogou Formation in Santanghu Basin to document the nature of organic matter (OM) in the context of an evolving lake system. The organic-rich samples (TOC 2.8–11.4 wt%; n = 10) were widely spaced from an ~ 200 m cored section, interpreted from textural and mineralogical evidence to document transition from a lower under-filled to an overlying balanced-filled lake. Organic matter is dominated by moderate to strongly fluorescent amorphous material with Type I geochemical signature (HI values 510–755; n = 10) occurring in a continuum from lamellar stringers, 10–20 μm thick, some ≥ 1 mm in length (possible microbial mat; preserved only in lower under-filled section) to finely-disseminated amorphous groundmass intimately intermixed with mineral matrix. Biomarkers for methanotrophs and photosynthetic cyanobacteria indicate a complex microbial consortium. A unicellular prasinophyte green alga(?), similar to Tasmanites in marine rocks, is present as discrete flattened discs 50–100 μm in diameter. Type III OM including vitrinite (some fluorescent) and inertinite also is abundant. Solid bitumen, indicating local kerogen conversion, fills voids and occurs throughout the cored section. Vitrinite reflectance values are 0.47–0.58%, consistent with strong OM fluorescence but may be “suppressed”. Other proxies, e.g., biomarker parameters, indicate the Lucaogou Formation is in the early oil window at this location. On average, slightly more amorphous OM and telalginite are present in the lower section, consistent with a shallow, stratified, saline environment with low sediment dilution. More inertinite is present in the upper section, indicating greater terrestrial influx and consistent with higher quartz and plagioclase content (dominantly authigenic chalcedony and albite). Laminated mudstones in the upper section indicate anoxia prevented bioturbation from benthic grazing, also indicating stratified water column conditions. A decrease upsection in authigenic dolomite with reciprocal increase of ankerite/siderite is consistent with decreasing salinity, as is an overall decrease in gammacerane index values. These observations suggest evolution from a shallow, stratified evaporative (saline) setting to a deeper, stratified freshwater basin with higher water input during Lucaogou deposition. The evolution from an under-filled to balance-filled lake in Santanghu Basin is similar to Lucaogou deposition in Junggar Basin, suggesting similar tectonic and climatic controls. Paleoclimate interpretations from other researchers in this area suggested an evolution from semi-arid to humid conditions during the Roadian; we interpret that the evolution from an under-filled to balanced-filled lake seen in our data is in response to climate change, and may represent increased groundwater delivery to the Santanghu Basin.

International Journal of Coal Geology↗

USGS2016

Comparison of geochemical data obtained using four brine sampling methods at the SECARB Phase III Anthropogenic Test CO2 injection site, Citronelle Oil Field, Alabama

The chemical composition of formation water and associated gases from the lower Cretaceous Paluxy Formation was determined using four different sampling methods at a characterization well in the Citronelle Oil Field, Alabama, as part of the Southeast Regional Carbon Sequestration Partnership (SECARB) Phase III Anthropogenic Test, which is an integrated carbon capture and storage project. In this study, formation water and gas samples were obtained from well D-9-8 #2 at Citronelle using gas lift, electric submersible pump, U-tube, and a downhole vacuum sampler (VS) and subjected to both field and laboratory analyses. Field chemical analyses included electrical conductivity, dissolved sulfide concentration, alkalinity, and pH; laboratory analyses included major, minor and trace elements, dissolved carbon, volatile fatty acids, free and dissolved gas species. The formation water obtained from this well is a Na–Ca–Cl-type brine with a salinity of about 200,000 mg/L total dissolved solids. Differences were evident between sampling methodologies, particularly in pH, Fe and alkalinity. There was little gas in samples, and gas composition results were strongly influenced by sampling methods. The results of the comparison demonstrate the difficulty and importance of preserving volatile analytes in samples, with the VS and U-tube system performing most favorably in this aspect.

International Journal of Coal Geology↗

USGS2016

Application of organic petrography in North American shale petroleum systems: A review

Organic petrography via incident light microscopy has broad application to shale petroleum systems, including delineation of thermal maturity windows and determination of organo-facies. Incident light microscopy allows practitioners the ability to identify various types of organic components and demonstrates that solid bitumen is the dominant organic matter occurring in shale plays of peak oil and gas window thermal maturity, whereas oil-prone Type I/II kerogens have converted to hydrocarbons and are not present. High magnification SEM observation of an interconnected organic porosity occurring in the solid bitumen of thermally mature shale reservoirs has enabled major advances in our understanding of hydrocarbon migration and storage in shale, but suffers from inability to confirm the type of organic matter present. Herein we review organic petrography applications in the North American shale plays through discussion of incident light photographic examples. In the first part of the manuscript we provide basic practical information on the measurement of organic reflectance and outline fluorescence microscopy and other petrographic approaches to the determination of thermal maturity. In the second half of the paper we discuss applications of organic petrography and SEM in all of the major shale petroleum systems in North America including tight oil plays such as the Bakken, Eagle Ford and Niobrara, and shale gas and condensate plays including the Barnett, Duvernay, Haynesville-Bossier, Marcellus, Utica, and Woodford, among others. Our review suggests systematic research employing correlative high resolution imaging techniques and in situ geochemical probing is needed to better document hydrocarbon storage, migration and wettability properties of solid bitumen at the pressure and temperature conditions of shale reservoirs.

International Journal of Coal Geology↗

USGS2017

Enhanced coal-dependent methanogenesis coupled with algal biofuels: Potential water recycle and carbon capture

Many coal beds contain microbial communities that can convert coal to natural gas (coalbed methane). Native microorganisms were obtained from Powder River Basin (PRB) coal seams with a diffusive microbial sampler placed downhole and used as an inoculum for enrichments with different nutrients to investigate microbially-enhanced coalbed methane production (MECoM). Coal-dependent methanogenesis more than doubled when yeast extract (YE) and several less complex components (proteins and amino acids) were added to the laboratory microcosms. Stimulated coal-dependent methanogenesis with peptone was 86% of that with YE while glutamate-stimulated activity was 65% of that with YE, and a vitamin mix had only 33% of the YE stimulated activity. For field application of MECoM, there is interest in identifying cost-effective alternatives to YE and other expensive nutrients. In laboratory studies, adding algal extract (AE) with lipids removed stimulated coal-dependent methanogenesis and the activity was 60% of that with YE at 27 d and almost 90% of YE activity at 1406 d. Analysis of British Thermal Unit (BTU) content of coal (a measure of potential energy yield) from long-term incubations indicated > 99.5% of BTU content remained after coalbed methane (CBM) stimulation with either AE or YE. Thus, the coal resource remains largely unchanged following stimulated microbial methane production. Algal CBM stimulation could lead to technologies that utilize coupled biological systems (photosynthesis and methane production) that sustainably enhance CBM production and generate algal biofuels while also sequestering carbon dioxide (CO 2 ).

International Journal of Coal Geology↗

USGS2017

Leaching of trace elements from Pittsburgh coal mill rejects compared with coal combustion products from a coal-fired power plant in Ohio, USA

We investigated the leachability of elements from mill rejects from the high-sulfur, bituminous Upper Pennsylvanian Pittsburgh coal, using the synthetic groundwater leaching procedure (SGLP), long-term leaching (LTL), and the U.S. Environmental Protection Agency's (EPA's) toxicity characteristic leaching procedure (TCLP), and compared their leaching behavior with that of three coal combustion products (CCPs)—bottom ash, economizer fly ash , and fly ash—from the same coal. None of the environmentally hazardous Resource Conservation and Recovery Act of 1976 (RCRA) metals analyzed in the leachates from the mill rejects or the CCPs exceeded U.S. EPA toxicity characteristics (As, Ba, Cd, Cr, Hg, Pb, and Se). Most trace elements leached the least from mill rejects and bottom ash and leached the most from fly ash. The elements Ca, Co, Mg, Mn, and Sr, however, were more concentrated in mill reject leachates than CCP leachates. Most trace elements increased in concentration with increasing SGLP and LTL leaching duration, but As and V decreased in concentration with time in mill reject leachates, suggesting sorption or precipitation of these elements was occurring.

Ohio↗

USGS2017

Identification of alginite and bituminite in rocks other than coal. 2006, 2009, and 2011 round robin exercises of the ICCP Identification of Dispersed Organic Matter Working Group

The paper presents results of round robin exercises on photomicrograph-based identification of dispersed organic matter in source rocks that represent a range of marine and lacustrine deposits from worldwide localities and cover a range of thermal maturities. The round robin exercises were conducted by the Identification of Dispersed Organic Matter Working Group (IDOM WG) of the International Committee for Coal and Organic Petrology (ICCP). The round robin exercises aimed to (1) assess the applicability of the established ICCP definitions of bituminite, (2) identify deficiencies and improve the existing nomenclatures, and (3) provide a basis for the revision of the bituminite and alginite definitions in the ICCP Handbook (Taylor et al., 1998). Three round robin exercises performed in 2006, 2009 and 2011 involved 18 participants from research laboratories at universities and within government and industry. Participants were asked to identify macerals on the basis of existing definitions in 129 photomicrographs taken in incident white light and fluorescent mode and also in fluorescence light mode at prolonged (15 min) blue light irradiation. The results indicate that the definition of telalginite permits its positive and satisfactory agreement among the participants. In contrast, the descriptive characteristics of lamalginite referring to film-like appearance (filamentous) and lack of inner or outer structure are insufficient and inadequate to enable an unequivocal discrimination between it and telalginite. Furthermore, based on the amorphous nature of bituminite and lack of adherence to its established description and character (Taylor et al., 1998), the highest discrepancies were observed in its identification. Differentiation of bituminite from a fluorescent groundmass and in some cases from lamalginite proved to be particularly challenging. The findings of these round robin exercises are useful for improving the identification of sedimentary organic matter in source rocks and may be an important foundation for the modification of the ICCP definitions of alginite and bituminite.

International Journal of Coal Geology↗

USGS2018

Pore-types and pore-network evolution in Upper Devonian-Lower Mississippian Woodford and Mississippian Barnett mudstones: Insights from laboratory thermal maturation and organic petrology

Pore-evolution models from immature organic-matter (OM) -rich Barnett (0.42%R o ) and Woodford (0.49%R o ) mudstones were compared with models previously developed from low-maturity OM-lean Boquillas (Eagle Ford-equivalent) mudstones to investigate whether (1) different mineralogy (siliceous vs. calcareous) exerts different catalytic and sorption effects and influences OM-pore origin and evolution; and (2) different types of macerals show different OM pore evolution history. Laboratory gold-tube pyrolysis, scanning electron microscopy (SEM) and thin-section petrography, organic petrography, and geochemical characterization were used to investigate the role of bulk mineralogy, maceral type, and thermal maturation on OM-pore evolution. Results suggest that mineralogy has little impact on OM-pore development and evolution. Macerals, identified using both SEM (platy OM, particulate OM, organic–mineral admixtures, Tasmanites ) and organic petrology (vitrinite, inertinite, amorphous organic matter [AOM]/bituminite, telalginite [ Leiosphaeridia , Tasmanites ]), do affect the origin and evolution of OM pores owing to differences in chemical compositions, generation kinetics, and activation-energy distributions between Tasmanites , matrix bituminite, and other types of macerals. Leiosphaeridia and Tasmanites in Woodford mudstone samples exhibit a delay in onset and a shorter period of petroleum generation and pore development compared to the matrix bituminite in the Barnett and Woodford mudstone samples. Pre-oil solid bitumen was observed to have migrated into initial primary mineral pore networks at the bitumen generation stage in both Barnett and Woodford samples. At higher levels of thermal maturation, the volume of primary mineral pores decreases and the pore volume composed of modified mineral pores and OM pores becomes greater. Pore evolution and pore-type heterogeneity in these mudstones is a function of the initial mineral pore network, types of kerogen and macerals, and generation kinetics of individual macerals upon thermal maturation.

Oklahoma↗