TWENTY YEARS OF CBM PRODUCTION AND MONITORING OF THE PINE RIVER SUBCROP: NO STREAM DEPLETION

Starting in 1994 a ground water, surface water and gas seepage monitoring network was set up in response to observed gas seepage near the subcrop of a producing Coal Bed Methane (CBM) formation and the Pine River in the San Juan Basin, southwestern Colorado. The initial null hypothesis was that CBM production was releasing gas at the subcrop due to downbasin CBM water pumping. The null hypothesis was tested using down hole video, packer testing, reservoir/seepage production analysis, temperature tracing, cation water quality, water age and potentiometric head trends. Based on the 20 years of observations, measurements and analysis the CBM null hypothesis was rejected. Since there was no hydraulic connection between the subcrop and CBM production, there was no depletion from the Pine River. A new null hypothesis that gas seepage was due to long term precipitation trends was formulated in 2000 by the author and continues to be accepted after 20 years of testing.