What is the difference between sandstone reservoirs and coal seam reservoirs?
A reservoir is a rock that is capable of containing hydrocarbons (natural gas or oil). Sandstone is one of the world’s most common reservoir rocks. Oil or gas is contained in the small spaces between the sandstone grains. Gas in sandstone is under enough pressure to naturally flow up a well to the surface. Gas reservoirs in coal are different, because the gas is attached to the coal at low pressure. To allow the gas to flow to the surface, the water pressure needs to be reduced. This allows the gas to flow up the well and to the surface.
