Pseudovitrinite: Possible Implications for Gas Saturation in Coals and Surrounding Rocks
Coal Petrography is for many a black science using terms that are for some not only incomprehensible but also in flux. For utilization purposes, the organic component of coal is generally broken down into reactive and non-reactive macerals, often with little further differentiation of the macerals. The main incentive to differentiate further is the recognition that the degree of reactivity in vitrinite macerals and the degree of non-reactivity in inert macerals, both vary.
Controls on Methane Adsorption Capacity of Lower Cretaceous Coals from Northeastern British Columbia, Canada: Part 2—Effect of Temperature, Pressure, Maceral Composition, and Mineral Matter on Adsorption
The effect of temperature, pressure, maceral composition, and mineral matter on the methane adsorption of coals from the Gething Formation was examined. Data was compared with coals from the Gates Formation in the same area and with coals from Australia. Adsorption capacity in the Gething coals appears to be moderately to strongly affected by the vitrinite (and pseudovitrinite) content and mineral matter, which does not only have a diluting effect, but also acts negatively on gas adsorptive capacity. Another explanation for the high gas adsorption capacity in the Gething coals may be related to the presence of free gas, which is more common when coals are below equilibrium moisture in a gas-saturated stratigraphy. Both Gething and Gates coals show an increase in gas-holding capacity, with increasing pressure as a function of vitrinite/inertinite ratio. Such an increase is absent in coals from the Bulli Seam, Sydney Basin, Australia.
Chemical variation as a function of lithotype and depth in Victorian brown coal
Victorian brown coal occurs in randomly sequenced stratified layers, known as lithotypes, which are distinguishable by their air-dried colour, maceral composition and many physical and chemical properties. The five major lithotypes can be related to generalized paleoenvironments of deposition and are known to influence many coal utilization parameters. Across the thick coal intervals which occur (up to 300 m) there is a small increase in coal rank observable via parameters such as % carbon and % volatiles. The purpose of this paper is to contrast the variation in the organic chemical nature of the coal occurring as a function of depth for a series of (nearly) identical lithotypes with that occurring as a function of lithotype. The authors have employed techniques giving both precise molecular level information (e.g., the distribution of extractable lipid classes) and average structural characterization of the whole coal (e.g., parameters derived from IR, solid state /sup 13/C-NMR, etc.). All of these techniques have been able to provide much deeper insights into the varying nature of the coal than the conventional elemental and functional group type analyses which have been carried out extensively in the past. american lignites: CA and MG.