The popularity of utilising Coal Seam Gas (CSG) is increasing throughout the world. Coal seam gas is primarily made up of methane gas and is found in coal seams at depths of 200m to 1000m below ground surface (BGS). The groundwater (hydrostatic pressure) holds the gas into the formation pore spaces. In order to release the gas, dewatering is used to allow the desorption of CSG from the formation, additionally hydraulic fracking can be used to stimulate and accelerate the flow of gas. However, there are some concerns associated with the extraction of CSG including the potential to introduce desorbed methane in the groundwater resources. In order to address these concerns it is necessary to monitor the aquifers to determine if the concentration of methane increases with the time.
An issue with testing the concentration of methane in groundwater from deep aquifers is that methane solubility in water is affected by the change in pressure. When the groundwater is brought up from the aquifer to the surface the change in pressure causes the methane to escape from the groundwater sample. Therefore, the current dissolved methane analysis performed in the water sample does not correctly quantify the total amount of methane present in the deep aquifer as the gas is released to the atmosphere once the sample is transported to the surface.