What is the ideal coal resource for UCG?
Coal thickness A thick coal seam, preferably 5m or greater. Thinner seams can be used but gas quality and hence the value of the gas is decreased. Mineral matter content Ash up to 55-60% can be tolerated but gas quality declines with higher values – optimally 45% or less. Groundwater Hydrostatic pressures must be maintained as they control the operating pressure in the gasifier – this favours depths greater than 200m to maintain a high hydrostatic pressure.Geological conditions Limited geological structural disturbance of the coal seams, as extraction blocks need to be laid out in a way similar to longwall mines. Geomechanical properties Surrounding strata must allow controlled cavity formation and ground response – again this favours depths greater than 200m but is specific to a site and gasification design.
