Estimation of the methane resources in the Richmond coal basin, Virginia
Methane, the natural by product of the coalification process, is held within coal beds under pressure. It is recognized that most of the methane present in coal occurs in the adsorbed state. The amount of methane present depends mainly on the pressure, temperature, adsorptive capacity and moisture content of the coal. Permeability, porosity, degree of fracturing of the coal and adjacent rocks and distance from the outcrop may also affect the methane content of a coal bed.
The methane content of coal seams can be estimated by the direct, indirect and the estimation methods. The first two methods require drinking of holes and taking samples, whereas, the third method estimates the methane content from a predetermined relationship involving the physical and chemical characteristics of coal. In this study, since no samples are to be taken and evaluation is to be based on existing data, to be estimation method has been chosen to determine the methane content in the basin. The coal resources have been estimated from the data and applied to the methane content determined, to arrive at the methane resources.
The results indicate that there may be 2 to 4 billion tons of coal in the basin and about 700 billion cubic feet of methane may be held within it.