Five Years of Domestic Well Monitoring for a Coal Bed Methane Project Area

in the San Juan Basin

By

Paul Oldaker

Hydrologist/Hydrogeologist, Steamboat Springs, CO

A San Juan Basin coal bed methane project area has completed five years of domestic well monitoring. The relatively shallow domestic wells, completed in alluvial and Tertiary Formations, had much less total dissolved solids concentrations compared to the CBM wells completed in the Fruitland Formation. The majority of domestic wells classified as mixed cation water type compared to sodium water type for the Fruitland Formation. Calcium, potassium, sodium and sulfate were key parameters to check for differences between the two data sets. The carbon 13 concentrations from carbon dioxide show the Fruitland Formation values to be much more enriched than domestic well values. Shallow depths are depleted in carbon 13 from carbon dioxide while deeper depths are enriched. The stable methane isotopes plot fairly closely together, but in two distinct areas for the two data sets. The carbon 13 values overlap while the Fruitland Formation deuterium values are more depleted than the domestic wells.

AAPG Search and Discovery Article #90004©2002 AAPG Rocky Mountain Section, Laramie, Wyoming