New Test Could Help Track Shale Gas Hazard in Shallow Groundwater

A new technique to spot contamination of shallow groundwater has been devised by a team of researchers from the Universities of Edinburgh and Glasgow, and the Scottish Universities Environmental Research Centre. The new technique can be used to track the contamination caused by unconventional gas extraction methods like fracking.

This new development could help to regulate the safety of coal bed methane extraction as well as shale gas extraction, which have raised concerns regarding contamination of ground water.

One of the techniques adopted for shale gas extraction is hydraulic fracturing, which is also called fracking. In order to release gas that is used as fuel, high-pressure fluids are utilized to split shale rocks that are found under the ground. Likewise, the extraction of coal bed methane from deep coal seams is done by drilling inside the coal. This reduces the pressure and subsequently releases the gas.

It was observed that drinking water becomes contaminated when large amounts of methane gas are released from deep below the ground following fracking operations. Serious allegations about this were made in the US, which emphasized the need for such a test.

Small quantities of methane gas, released from shallow natural sources, are generally present in groundwater and these are deemed harmless. The latest technique, developed by the research team, provides new means to trace the presence of methane gas by spotting even small quantities of inactive natural gases, also called noble gases. The unique fingerprints of methane differ based on the origin and depth of methane. These details help scientists to identify the source of methane.

The researchers have successfully recorded these unique traces of methane in many exploratory shale gas and coal bed methane wells in and around the UK. The team has presented their latest results at the European Geosciences Union Conference held in Vienna.

The fingerprint test of methane can be effectively used to find the origin of methane at various exploration sites. If the methane levels have increased in the ground water level after the extraction/exploration activity, appropriate actions can then be taken to protect ground water quality.

This technique was inspired by a process that was used for tracking possible leakage of CO₂ gas from the underground storage sites.

Creating this fingerprint test will enable gas exploration and extraction to be carried out responsibly and should help address public concerns over this technology. It is important that careful monitoring of methane levels in nearby waters is carried out when commercial extraction begins.

Dr Stuart Gilfillan, University of Edinburgh's School of GeoSciences