About Coal Seam Gas

How Coal Seam Gas is Formed

The States of New South Wales and Queensland did not always have huge dry interiors with a verdant green strip close to the coast.  Millions of years ago, during the Cretaceous Period, a huge inland lake existed where rivers and rainwater deposited rich organic sediments into a series of enormous sedimentary basins.  These basins extend from the north in Queensland - the Gallilee, Bowen, and Surat basins - into New South Wales - the Clarence Moreton and Gunnedah basins.  Over millions of years these basins filled with remnants of vegetation and water life to form settled layers of organic material.

As these layers settled and more layers of organic material were deposited over millions of years, a heavy pressure of overburden was established. This, combined with geothermal heat from the earth, created coal, gas and oil as well as other hydrocarbons.

Coals contain both gas and water and gas produced from coals is called coal seam gas ("CSG") or coal seam methane ("CSM").  This form of natural gas is trapped in coal seams by the pressure of being buried underground. 

How Coal Seam Gas is Extracted

Metgasco applies advanced drilling and production techniques to extract coal seam gas.  We produce gas from certain seams by drilling a vertical well to between 300 to 700 metres from the surface.  The well is then cased to prevent any water from upper acquifers leaking into the well.  We then drill horizontally along the coal seam to a distance of up to 1,000 metres.  The well is then lined with perforated steel casing.  Water and gas are then pumped from the well and separated at the well head.  This process of taking water out of the coal seams lowers the pressure in the well and allows gas to flow to the wellhead.

What is Coal Seam Gas Used For?

Coal seam gas is a very pure source of natural gas, usually with very high (90%+) methane content.  It is used by households for heating and cooking; in industrial energy applications; and for low greenhouse gas emission power generation.  It has become a very important source of energy in Australia and now supplies over 60% of the total gas market in Queensland.