2012-09-06_REVISION - M2008070 (29)

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circulation may be sufficient to create more favorable trapping conditions (Figure A3 -5), may be a better target area for coalbed methane production exploration. These exploration target zones could possibly have sufficient meteoric groundwater circulation to meet the water quality criterion of USDWs. However, Figure A3 -3 shows that the depths to coals in the targeted methane producing zones (Figure A3 -5) are greater than 4,000 feet below ground surface and therefore, are not likely to contain water that would meet the USDW quality criterion of less than 10,000 mg/L TDS. Currently, test - drilling information is insufficient to determine if this is the case. Nevertheless, due to the very low permeability, great depth, and expected poor water quality of the targeted coalbed methane producing zones, conflicts with USDWs are considered to be of very low probability. 3.3 Coalbed Methane Production Activity Measurements of coal permeabilities in the Piceance Basin have shown that the deep coals typical of the basin are much less permeable than coals in top - producing coalbed methane basins such as the San Juan Basin in Colorado (Quarterly Review, 1993). Consequently, operators rely on large hydraulic fractures to produce coalbed methane from the deep, low permeability coals (Quarterly Review, 1993). Exploration for coalbed methane began in the basin during the early 1980s, but viable commercial production did not begin until 1989 (Quarterly Review, 1993). The first well to commercially produce coalbed methane from the Piceance Basin, Exxon's Vega No. 2 well in Mesa County, went off -line in 1983 (Quarterly Review, 1993). Amoco Production Company attempted multi -well coalbed methane development in the late 1980s, and finally ceased activity in 1989. Commercial production was finally achieved in 1989 in the Parachute fields operated by Barrett Resources. Barrett Resources drilled 68 wells in 1990 and had planned for 22 more in 1991 (Western Oil World, 1991). The wells targeted both coals and sandstone within the Cameo Coal Zone and the Mesaverde sandstones, just above the Cameo coals. Other operators soon followed suit, including Fuelco at White River Dome field in the northern part of the basin (Figure A3 -1), Conquest Oil Company near Barretts Resource's production in the central part of the basin, Chevron USA Inc., and many others. However, not all operators were successful in locating or producing coalbed gas. Ultimately, Barrett found the sandstones to be far more productive than the coalbeds, and attempts to complete wells in the coalbeds were largely abandoned. According to the Colorado Geological Survey (2002), some operators are having success in their pilot coalbed methane production program in White River Dome Field northwest of Meeker. Their success is attributed to the extensive natural fracturing found in the coal seams at White River Dome. Fracturing may be particularly extensive as a result of the formation of the White River anticline and the proximity to the large Danforth Hills Mesaverde outcrop. As a result, operators are taking another look at coalbed methane Evaluation of Impacts to Underground Sources of Drinking Water by Hydraulic Fracturing of Coalbed Methane Reservoirs June 2004 A3 -5