In a Safety Advisory from May, 2010, the Oil and Gas Commission of British Columbia announced that it is aware of 18 incidents in Canada where hydraulic fracturing of shale gas wells led to unintended communication with other gas wells, fractures created during fracturing of adjacent gas wells, or another leg of a multi-lateral well. Communication occurred when wells were separated as much as 715 meters, which (for those of us south of the border) is almost half a mile. If not controlled safely, these incidents can lead to a blow-out.As I've blogged about in the past, onshore blow-outs can have serious health and safety consequences.
According to the British Columbia Oil and Gas Commission, "Fracture propagation via large scale hydraulic fracturing operations has proven difficult to predict."