thickness) Separation At least 1500 ft (460 m) Debateable, but there is None, depending on ~500 ft as of year 2000 None (but not if there from potable separation (water wells perhaps a minimum of location (water wells production, but potential are producing water wells aquifer range from 500-2000 ft) 1000 ft (300 m) 50400 ft) (15-120 m) for no separation as in the CSG zones) (150-610 m) separation from any region is developed producing aquifer since wells typically 50100 ft) water supplies in this (15-30 m) sparsely populated area are derived from surface sources or shallow alluvial aquifers Hydraulic 1500-3500 barrels Water, gel and foam Water, gel and foam Water, gel and foam Water and gel, often fracturing (180420 m3) of water or fractures have all been fractures have all been fractures have all been >100 000 barrels methods cross-linked gel hydraulic tested. Not clear what tested. Not clear what tested. Not clear what (12 000 m3), but not fractures used to produce comprises standard comprises standard comprises standard clear if sustained from deep, low practice practice practice because HF believed to permeability coals increase water production Water loss None reported None reported None reported None reported None reported incidents None reported None reported None reported None reported None reported Contamination incidents Source: US EPA (2004), unless otherwise noted
thickness) Separation from potable aquifer At least 1500 ft (460 m) separation (water wells range from 500-2000 ft) (150-610 m) Debateable, but there is perhaps a minimum of 1000 ft (300 m) separation from any producing aquifer since water supplies in this sparsely populated area are derived from surface sources or shallow alluvial aquifers None, depending on location (water wells 50400 ft) (15-120 m) ~500 ft as of year 2000 production, but potential for no separation as region is developed wells typically 50100 ft) (15-30 m) None (but not if there are producing water wells in the CSG zones) Hydraulic fracturing methods 1500-3500 barrels (180420 m3) of water or cross-linked gel hydraulic fractures used to produce from deep, low permeability coals Water, gel and foam fractures have all been tested. Not clear what comprises standard practice Water, gel and foam fractures have all been tested. Not clear what comprises standard practice Water, gel and foam fractures have all been tested. Not clear what comprises standard practice Water and gel, often >100 000 barrels (12 000 m3), but not clear if sustained because HF believed to increase water production Water loss incidents None reported None reported None reported None reported None reported Contamination incidents None reported None reported None reported None reported None reported Source: US EPA (2004), unless otherwise noted