The Fruitland Formation Coal-Bed Methane Field of the San Juan Basin,

New Mexico and Colorado -- Multiple Discrete Reservoirs

By

Bradford C. Boyce

CDX Rockies, LLC, Durango, CO

Brent Hale

Williams, Tulsa, OK

James E. Fassett

U.S. Geological Survey, Scientist Emeritus/Independent Geologist, Santa Fe, NM

The Fruitland coal-bed methane (CBM) field of the San Juan Basin is the largest US onshore gas discovery since the late 1970s, and today is the world’s largest CBM field with a cumulative production of 9 TCFG to date and more than 55 TCFG in place. Careful, detailed analysis of Fruitland CBM production has demonstrated that even though Fruitland coals underlie the entire San Juan Basin, the Fruitland CBM field comprises at least six reservoirs, each with distinct geologic and reservoir characteristics. The northwest-trending Fruitland Fairway is the most productive of these reservoirs because coals there are highly fractured with high permeability; wells within this reservoir produce more than 1 MMCFGD and ultimate recoveries may reach or exceed 75% of the original gas in place (OGIP) on 320 acre well spacing. The second reservoir is north of the Fairway, mostly in Colorado, and there coals are less permeable and wells there will probably produce less than 50% of OGIP on 160 acre spacing. The other four reservoirs are south or southeast of the Fairway and Fruitland coals in those areas are also far less permeable than those in the Fairway. These four areas are partially defined on the basis of the presence or absence of water, heavy hydrocarbons and waxes, and permeability differences. Ultimate CBM gas recovery in these four areas will probably be less than 25% OGIP on 160 acre spacing.

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