Musings: New Concern Over Hydraulic Fracturing May Impact Its Use
Last spring two small earthquakes struck an area near Blackpool, England, where Cuadrilla Resources, Ltd. drilled and hydraulically fractured two shale gas wells. The earthquakes – the April one was 2.3 on the Richter scale and the May one was 1.5 – have now been determined to have been caused by the fracturing activity. Shortly after the earthquakes, Cuadrilla voluntarily ceased fracturing until a study was conducted on the possible linkage between fracturing and the seismic activity. Last week the study, Geomechanical Study of Bowland Shale Seismicity, funded by Cuadrilla, was released and it pointed to "strong evidence" that the two minor earthquakes and 48 weaker seismic events resulted from the company’s fracturing efforts. At the same time, the report stated that the events were the result of a "rare combination of geological factors." This suggests that the linkage between hydraulic fracturing and earthquakes may not be as direct as suggested by the conclusions of the study.
This report comes at the same time a previously unreported study conducted by the Oklahoma Geologic Survey showed a linkage between fracturing and earthquakes came to light. The study, Examination of Possibly Induced Seismicity from Hydraulic Fracturing in the Eola Field, Garvin County, Oklahoma, is currently being prepared for peer review. The study shows that a series of small earthquakes last January near Elmore City can be attributed to hydraulic fracturing activity in the nearby field.
The UK study will be considered by regulators before they take any action. After the earthquakes, Cuadrilla engaged an independent team of seismic experts and the study was prepared in consultation with the Department of Energy and Climate Change who regulates fracturing. The report said that the combination of seismic factors and local geology conditions was rare and unlikely to occur together in the future. As the report concluded, "If these factors were to combine again in the future, local geology limits seismic events to around magnitude 3 on the Richter scale as a worst-case scenario." The conclusion is important because recently Cuadrilla announced a major shale gas discovery in the UK, but development has been delayed until this study was completed. Now it may have to await a decision by the regulators.
These two studies come at a difficult time for the shale gas industry as they add fuel to the environmental objections to this extraction practice. Recently the Environmental Protection Agency announced the outline for its detailed study of hydraulic fracturing and possible ground water pollution. That study has already drawn significant attention and anticipation. And even though the earthquakes were very small and caused little or no structural damage or any injuries, they are scary for people in the area when they happen. Additionally, they raise concerns about the impact of the fracturing pressures being exerted on the substrata of the earth and the possibility that those stresses can create other unknown problems such as aquifer contamination. All of this may cause regulators and politicians to want to slowdown the shale gas revolution.
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