Draft Genome Sequence of Desulfovibrio sp. Strain CSMB_222, Isolated from Coal Seam Formation Water

Subsurface coal seams contain microbial consortia with various taxa, each with a different role in the degradation of coal organic matter. This study presents the sequenced and annotated genome of Desulfovibrio sp. strain CSMB_222, a bacterium isolated from eastern Australian coal seams.

Paleogeothermal and paleotectonic reconstructions based on vitrinite thermometry data (on the example of the upper paleozoic deposits of the Dnieper-Donets depression and adjacent areas of Donbass)

The article is devoted to paleogeothermal and paleotectonic reconstructions based on the results of processing the vitrinite reflectance data array of coal organic matter of the Upper Paleozoic sediments from the Don-Dnieper Downwarp (within the Dnieper-Donets Depression and adjacent areas of Donbass). It was found that paleogeothermal parameters changed under the influence of geotectonic, magmatic and lithofacies formation conditions of the Upper Paleozoic deposits. Analysis of changes and regularities distribution of paleogeothermal characteristics made it possible to assess the evolution of the thermal field, changes in the tectonic movements character, to identify the role of volcanism, deep faults geodynamics, lithosphere thickness in the thermal history of the region under study. It is shown that with the help of paleostructural analysis, based on data on the thermal maturity degree of coal organic matter, it is possible to judge the activity changes of tectonic structures in time, the formation sequence, to establish the amplitudes of their mutual displacement and rank according to oil and gas potential. Based on the results of the work, maps of the paleogeothermal gradients distribution and the amplitudes of rock masses vertical displacements were constructed. The presented maps should be considered as a universal information material that can be used to determine the features of the regional distribution of the above parameters, as well as become an important tool in the study of tectonic and thermal history, identification changes trends and distribution patterns of paleo­geothermal characteristics.

Hydrogeochemical Characteristics and Water–Rock Interactions of Coalbed-Produced Water Derived from the Dafosi Biogenic Gas Field in the Southern Margin of Ordos Basin, China

The hydrogeochemical characteristics of coalbed-produced water can provide insights into the sources of ions and water, the groundwater environments, hydrodynamic conditions, and water-rock interactions of depositional basins. To study the water-rock reaction process and reveal whether there is a microbial activity in the groundwater, a case of the Dafosi biogenic gas field was chosen by testing the ionic concentrations and hydrogen and oxygen isotopic compositions of coalbed-produced water and employing R-type cluster and principal component analyses. The results showed that Na+, Cl − , and HCO3- are the principal ions in the coalbed-produced water, while the water type is mainly a Na–Cl. Due to the hydrolysis of HCO3-, the pH in this region was controlled primarily by HCO3-. As the main cation in water, Na+ contributed substantially to the total dissolved solids. Na+ is also related to the exchange between rock-bound Na+ and Ca2+ and Mg2+ in water or surrounding rocks. The coalbed-produced water’s oxygen isotopes displayed a characteristic 18O drift and enrichment, indicating that the 16O isotope in the water was preferentially exchanged with the coal organic matter. Early evaporation is also contributed to the enrichment of TDS (total dissolved solids) and 18O in the water. The central part of the study area, including the Qijia anticline, was affected by the Yanshanian uplift and denudation and subsequently developed a water-conducting fissure zone and was recharged atmospheric precipitation; these conditions were conducive to the formation of secondary biogenic gas.

Visean palaeoincisions as centers of fluid-generation in the Kama coal basin

The paper considers palaeoincisions in the Turnean limestones of the Volga-Ural basin, made by alluvial-deluvial sediments of the Visean age and containing interlayers of coals. Processes occurring in these sediments (catagenic reduction of thickness of coal beds and coal-bearing mudstones, aggressive influence of products of defluidization of coal organic matter on the host rocks, etc.) strengthen the fluid dynamic heterogeneity of intracrustal deposits and contribute to emigration of hydrocarbons (HC). The main oil-and-gas-generating strata in the Carboniferous section include rocks of the Tournaisian stage and the Bobrikovsky horizon of the Viseian stage. Palaeoincisions, along with the area distribution of Viseian coals, can be considered as centers of fluid generation, including liquid and gas HC.

THERMAL DECOMPOSITION OF BARZAS COALS

Thermal decomposition processes of two types of Barzas sapromixites - a tile-like modification (“tile”) and a product of its weathering (“exfoliated tile”) - have been investigated in various media (air and helium). It has been shown that in the course of temperature-programmed decomposition (10 °C/min) of these forms of tile-like Barzas sapromixite, in both oxidizing (air) and inert (helium) atmospheres, four main temperature ranges can be distinguished: 1) < 150 °C - removal of adsorbed water (this temperature region is more pronounced for the weathered form of tile-like Barzas sapromixite); 2) 150-350 °C - removal of low molecular weight volatile components of coal in helium environment (with their simultaneous ignition in case of the decomposition in air); 3) 350-550 °C - the temperature region of primary or fast coal pyrolysis in an inert medium; in an oxidative medium, this stage of pyrolysis is accompanied by the burning of released tarry substances; 4) > 550 °C - the temperature region of secondary or high-temperature coal pyrolysis to form semi-coke in helium atmosphere, or the region of burning this semi-coke in air medium. Thermal breakdown processes of “exfoliated tiles” in the temperature range of the most intensive decomposition (350-550 °C) have been found to require less energy consumptions than the similar processes for tile-like Barzas coals (by 72-73 kJ/mol for both gas media of thermal treatment). It is supposed that the differences observed in thermal behavior of Barzas sapromixite forms under investigation may be related to the different contents of mineral components and their effects on the thermal decomposition of coal organic matter.

Deashing and desulfurization of subbituminous coal from the East field (Bogovina Basin, Serbia) - insights from chemical leaching

The study is focused to determine the most effective chemical leaching process for simultaneous demineralization/deashing and desulfurization of subbituminous coal from the Bogovina Basin. Coal was treated for 30 minutes, at different temperatures, using variable concentrations of hydro-chloric, nitric, acetic and citric acids; hydrogen peroxide, mixture of hydrogen peroxide and nitric acid (pH 2), as well as by the stepwise leaching process (nitric acid + mixture of hydrogen peroxide and nitric acid, pH 2). The changes in mineral composition, caused by chemical leaching, are followed using X-ray diffraction, whereas alterations of coal organic matter are tracked by Fourier-transform infrared spectroscopy and content of fixed carbon. Inorganic acid leaching, regardless of temperature and acid concentration, enabled successful deashing of coal, whereas percent of desulfurization was insufficient. Organic acid leaching was not satisfactory for both, deashing and desulfurization. Leaching by H2O2 and H2O2/HNO3 mixture (pH 2) resulted in moderate desulfurization, but ash reduction was low. The most suitable method for simultaneous effective ash (78 wt.%) and sulfur (66 wt.%) removal from Bogovina coal is the two-step leaching, combining 10 vol.% HNO3 and mixture of 35 vol.% H2O2/10 vol.% HNO3 of pH 2 at 60?C.

Who eats what? Unravelling microbial conversion of coal to methane

ABSTRACTMicrobial communities in subsurface coal seams are responsible for the conversion of coal organic matter to methane. This process has important implications for both energy production and our understanding of global carbon cycling. Despite the environmental and economic importance of this process, little is known about which components of the heterogeneous coal organic matter are biodegradable under methanogenic conditions. Similarly, little is known about which taxa in coal seams carry out the initial stages of coal organics degradation. To identify the biodegradable components of coal and the microorganisms responsible for their breakdown, a subbituminous coal was fractionated into a number of chemical compound classes which were used as the sole carbon source for growth by a coal seam microbial community. This study identifies 65 microbial taxa able to proliferate on specific coal fractions and demonstrates a surprising level of substrate specificity among members of this coal-degrading microbial consortia. Additionally, coal kerogen, the solvent-insoluble organic component of coal often considered recalcitrant to microbial degradation, appeared to be readily converted to methane by microbial degradation. These findings challenge our understanding of coal organic matter catabolism and provide insights into the catabolic roles of individual coal seam bacteria.

Destabilization of the hard coal microstructure by a weak electric field

This study aims to analyse physical and chemical changes in hard coal samples under the influence of low-intensity electric fields in comparison to the fragments of ejected coal, as well as the coal samples selected from the zones of high and low outburst hazard. We used physical methods including X-raying, electron paramagnetic resonance, thermogravimetric analysis, differential scanning calorimetry, laser diffraction analysis of particle sizes, IR-spectrometry, nuclear magnetic resonance, and Raman spectroscopy. It has been shown that destruction of coal organic matter (COM) can be caused not only by mechanical impacts or thermal influences but also weak electric fields. Scientific novelty consists in the fact that for the first time we established the identity of the COM destruction mechanism of mechanical-chemical activation and weak electric fields influencing on the previously destabilized coal microstructure. The destruction mechanism is based on thermal field regularities in both cases. The results obtained are of practical significance for the technologies of coal conversion to other products. The research results can be useful in the development of methods for reducing outburst hazard in coal mines.