Analysis of the Influence of Coal Petrography on the Proper Application of the Unipore and Bidisperse Models of Methane Diffusion

The analysis of phenomena related to gas transport in hard coal is important with regard to the energetic use of coal bed methane (CBM), the reduction of greenhouse gas emissions to the atmosphere (CO2) and the prevention of natural hazards such as methane hazards and gas and rock outbursts. This article presents issues concerning the feasibility and scope of applying the unipore and bidisperse diffusion models to obtain knowledge concerning the kinetics of methane sorption and its diffusion in the carbon structure, depending on its petrography. Laboratory tests were carried out on coal samples which varied in terms of petrography. Quantitative point analyses were carried out, based on which content of groups of macerals was determined. The degree of coalification of coal samples was also determined based on measurements of vitrinite reflectivity R0 and the volatile matter content Vdaf. Sorption kinetics were also investigated, and attempts were made to adjust the unipore and bidisperse models to the real sorption kinetic courses. This allowed the identification of appropriate coefficients controlling the course of sorption in mathematical models. An attempt was also made to assess the possibility of applying a given model to properly describe the phenomenon of methane sorption on hard coal.

Maceral Association in Coal-bearing Formation of Mae Than Coal Mine in Lampang, Thailand - Implication for Depositional Environment

The Mae Than Basin in Lampang Province contains low-ranked coal reserves of northern Thailand. Coal seams and ball clays were mined in the southern part of the basin. This study focuses on the coal petrography of coal samples collected from the upper coal seam in the Mae Than Coal Mine. Both the organic and inorganic constituents provide information on the nature and characteristics of the coal, reflecting the physical and chemical behaviors of coal. Petrological analysis reveals that the Mae Than coals contain more huminite than liptinite macerals, while inertinite is negligible. Huminite occurs mainly in the form of texto-ulminite, textinite, densinite, and gelinite. Liptinite consists of sporinite, cutinite, resinite, suberinite, liptodetrinite, and terpenite. The morphology of cutinite, sporinite, and the presence of terpenite indicate that the peat-forming vegetation may consist of conifers. In addition to the macerals, the coal samples contain a small to moderate amount of mineral matter. Silica and clay minerals are the main minerals found in the cavities and between the cracks of the coals. The assemblage of macerals and mineral matter indicates that the Mae Than coals were formed mainly from common peat-forming vegetation, possibly conifers, in a freshwater forest swamp or mire in a warm temperate climate. In addition, the high degree of preservation of the macerals indicates a high water table and suggests rheotrophic, anoxic, limnotelmatic to telmatic conditions during deposition.

Construct a Paleo-Limnological Environment Based on Coal Petrography; Case Study, Two Selected Coal Seams, North Crowsnest Open-Pit Mine, Canada

The Crowsnest coalfield is a separated structural coalfield at the East Kootenay basin within southeast British Columbia. Selected Jurassic-Cretaceous two coals seam S-10 and S-C of the Mist-Mountain formation were investigated from the points of coal petrography to construct a Paleo-limnological setting. Twenty-two channel coal samples were assembled and measured from S-10 and S-C coal seams. Vitrinite reflectance measuring of the S-10 coal concern to low-volatile bituminous (1.61, on average). While the vitrinite reflectance measurements of S-C coal seam show an average value of 0.98 related to high-volatile bituminous. Petrographic analysis demonstrates that the S-10 coal seam appears to be rich in inertinite than the S-C coal seam that appears rich in vitrinite. Applying coal facies indices of Tissue Preservation Index, Gelification Index, Ground Water Index Vegetation Index and coal facies diagrams for the studied coal seams aid to suggest a condition of the depositional Paleo-environments. The results promote Paleo-depositional sites of telmatic to limno-telmatic setting of rheotropic systems swamp. The obtained results show a trend of increase in both herbaceous flora and anoxic waterlogged limo-telmatic setting toward the younger coal seam S-C than the older S-10 coal seam.

Direct signs of oil-generation in the rocks of Bazhenov Suite

Nowadays, the term “organic petrology” is widely used for the microscopic study of the organic matter (OM) of rocks. In the world, there are a large number of articles describing organic macerals in regions where shale oil and gas are produced. It is no coincidence that the new term “organic petrology” appeared instead of “coal petrography” since new macerals were found and described in the dispersed organic matter. So, along with alginites (previously the only term describing the oil-source sapropel-type OM), bituminite and bitumen appeared. Bituminite is heterogeneous, so it has varieties as “post-mature bituminite” and “atypical bituminite”. One of the typical components of the Bazhenov formation, along with described above, are the remains of soft radiolarians bodies. All of these organic macerals have a similar reflectance index with small differences. Long-term studies of the OM rocks of the West Siberian basin have revealed indications of oil generation, which are easily established by standard microscopic studies. These indications include a change in the colour of macerals, a different glow of oil-source components (all from the liptinite group), the appearance of bitumen films, the appearance of post-mature bituminite, the appearance of secondary porosity.