Once a potential source of natural gas has been identified, extensive studies are undertaken to assess the viability of the gas reserves, seismic surveys are undertaken, and test wells are drilled in the area of interest to test the quality of the gas resource.
Coal Seam Gas
Coal Seam Gas (CSG) reserves are generally shallower than other natural gas reserves, meaning they are easier to access, while shale and tight gas reserves are deeper underground.
If a gasfield is found to be scientifically and commercially viable, then production can commence.
Production usually involves drilling multiple wells to access the gas reserves. These wells are either vertically or horizontally drilled, depending on where the gas reserves lie within the coal seam, shale or tight sandstone.
Coal seams store both water and gas. When a well is drilled, the water and gas are pumped out. The NSW Government’s Office of Coal Seam Gas – an independent regulatory authority – has produced a useful explanatory video.
Shale and Tight Gas
Shale and tight gas wells are drilled to depths below the surface of between 2 and 5 kilometres and may require hydraulic fracturing to extract the resource. Shale and tight gas wells are drilled vertically during an exploration and appraisal program.
They are then potentially drilled horizontally depending on the structure of the target formation.