New Mexico Geological Society Annual Spring Meeting — Abstracts

Coalbed methane is a newly emerging resource for the Raton Basin in New Mexico. In recent years a stronger emphasis has been placed on understanding the hydrogeology related to coalbed methane production because of the inextricable relationship of water and gas in such reservoirs. The purpose of this study was to investigate how hydrogeology influences coalbed methane potential in the study area. Surface and subsurface water chemistry, potentiometric surface, and permeability data were analyzed. Water balances were performed for two watersheds in the study area given historical rainfall records, stream flow measurements, groundwater well levels, and evapotranspiration estimates. Well logs and production data were also examined. The results indicate that the subsurface aquifer system in which the coalbeds are located is under-pressured. It is confined by an amalgamation of low permeability lithologies overlying and intermixing with the coalbeds. Matrix permeability shows no apparent distinction between lithologies in the aquifer. However, hydraulic conductivity tests inclusive of fracture permeability show correlation to lithology, with mudstones having the highest conductivity, followed by coals, and then sandstones. Increased water production in wells proximal to igneous intrusives supports the notion of increased connectivity due to fracturing around such features. These findings, when compared to coalbed methane production data, suggest a possible connection between hydrogeology and coalbed methane potential.