GEOLOGIC CONTROLS ON COALBED METHANE PRODUCTION DOMAINS WITHIN THE SOUTHERN RATON BASIN OF NEW MEXICO

The southern portion of the Raton Basin, located in northern New Mexico, is being jointly developed by Vermejo Park Ranch and El Paso Production Company. Analyses of field data, core, geophysical data (well logs and seismic) and production profiles, suggest that regions with different production characteristics can be delineated based on geologic controls. These include, but are not limited to; large-scale structures, faulting, fractures, hydrodynamics, sedimentology, and present-day topography/depth of erosion.

Production patterns vary across the Vermejo Park Ranch relative to location with respect to the Vermejo Park anticline. Large-scale structures, such as this anticline, have generated local fracture patterns that are superimposed over the regional fracture set. Large structures can also create unique present-day topographic/depth of erosion patterns. For example the Vermejo Park and Tercio anticlines are breached anticlines with surface exposures of the Pierre Shale. Thus the entire vertical column of the coalbed methane play is exposed at the surface around these structures, altering the influx and outflow of meteoric waters into the local coal reservoirs. Such structures influence the hydrodynamic flow and production patterns across the basin.

Production around the Vermejo Park Anticline can be divided into quadrants. Coalbed methane production from the SW quadrant has fresher water, more N-S fractures, lower water cut, higher reservoir pressures, greater gas production and a conventional hyperbolic gas decline curve compared to the NE quadrant which has a higher water cut, lower reservoir pressures, lower production rates and typical reverse-decline coalbed methane production curves. The smaller scale geologic controls of fluid flow directionality relative to these production domains will also be discussed.