Shale gas in Canada : Gaz de schist au Canada : Risques environnementaux et réglementation

When drilling the well, multiple lengths (“strings”) of steel casing are lowered into the wellbore to different depths and cemented into place, creating several layers of steel 10 and cement between the inside of the well and the surrounding environment. [...] The challenge of well integrity is amplified by the potentially high number of wells associated with large-scale development of shale gas and the chemical additives used in fracturing fluids. [...] According to the CCA, the oil and gas industry has substantially improved the 60 practices used for the cement sealing of wells over the past decade. [...] The particularities of certain shale gas plays can also influence the amount of emissions during development of the resource. [...] A very small fraction of injection and extraction activities at the hundreds of thousands of oil and gas wells in the U. S. have induced seismicity 145 noticeable to the public.