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Background information on various unconventional oil and gas (UOG) techniques, including hydraulic fracturing ("fracking") and underground coal gasification.
Techniques such as horizontal drilling, dewatering, and hydraulic fracturing can be used to access and retrieve the natural gas contained within the ground.
Hydraulic fracturing, also known as “fracking”, is used for shale gas but not typically coal bed methane. Globally, the use of fracturing techniques to stimulate the recovery of oil and gas has expanded greatly in the last decade. Hydraulic fracturing methods have a wide range of applications, including enhancing water flow in aquifers used for drinking water.
The process of hydraulic fracturing involves pumping water into the source rock, which is typically located 1-3 km below ground, at high pressure so that the rock fractures and releases the trapped gas. This water also contains a small percentage of sand (~5%) and chemicals (<1%) to improve efficiency of the operation.
Extracting coal bed methane typically requires water to be drained from the coal seam to release pressure (known as dewatering), without hydraulic fracturing.
Underground Coal Gasification (UCG) is an industrial process which utilises high pressure combustion to convert coal in non-mined coal seams into gas. The technology used for UCG differs considerably from technology utilised for shale oil and gas and coal bed methane. UCG is not a fracking technique.