WHERE ARE CBM RESOURCES LOCATED?

The majority of CBM development has been conducted in the West, South, and, to a smaller degree,

In addition to those basins another 1,000 Tcf of methane may also be located in Alaska (Lang moo). It's important to recognize that estimates differ greatly, based on conflicting hypothesis's and differences between proven reserves and those that are economically or technically recoverable.

HOW DO THE WESTERN CBM BASINS COMPARE?

The major producing CBM basins in the Rocky Mountain region include the San Juan, Raton, Uinta, and the Powder River Basin. Potential or initial development is being considered for the Piceance, Green River, and Denver basins.

Each coal basin is different and poses its own unique set of development criteria and exploration challenges. Due to these differences, developments in various basins cause distinct changes to the surrounding communities and ecosystems. Some basins have been produced for many years and are nearing their peak while others are in the initial stages of development and some have still yet to be considered. Some basins produce good quality water that can be used for a variety of beneficial uses including irrigation, dust control, livestock watering, wetlands construction, wildlife source ponds, and even human consumption (ALL 2003), while other basins have poor quality water that must be managed for proper disposal. The common factor among CBM basins in the Rocky Mountains is that they each have unique characteristics. Operators take a long hard look at the various basins regional geology, coal types and characteristics, existing infrastructure, surrounding ecosystems and production potential before any investments are contemplated. New technologies are being advanced each year, which make some seemingly non-profitable basins more economic as differences are evaluated time and again. Table 2 summarizes the key characteristics of producing CBM basins in the Rocky Mountain Region of the United States.

Text Box: Table 2 Comparison of Producing CBM Basins in the Rocky Mountain Region Basin San Juan Raton Uinta Powder River State Location NM, CO NM, CO UT WY, MT Drilling Method Air Percussion Air Percussion Air Percussion Air-Water Completion Methods Cased Hole Perforate/Multistage Cased Hole Perforate/Multistage N2 Foam/Sand Cased Hole Perforate/Multistage X-LinklSand Open-hole Under-ream Producing Wells 2,550 694 558 10,358 Primary Water Disposal Methods Injection Deep Injection Deep Injection Surface Discharge, Beneficial Use Water Lift Method Rod Pump and Cavity Progressive Prog Rod Pump Rod Pump Electric Pump Average water Production per well 25 Bbl/day 266 Bbl/day 215 Bbl/Day 400 Bbl/day Coal Rank Sub-bituminous high-volatile bituminous high-volatile bituminous Sub-bituminous Well Depth (feet) 550-4000 bsl 400-4000 bsl 2000-7000 bsl 200-2500 bsl Net Coal Thickness 20-80 feet 10-40 feet 10-40 feet 75 feet Gas Content 350-450 scf/ton 50-400 scf/ton 250-400 scf/ton 30 scf/ton Well Spacing 320-160 acres 160 acres 160 acres 80 acres Average Well Cost $275,000 $330,000 $375,000 $75,000 Average Well Reserves 10 Bcf 1.8 Bcf 1.5 Bcf 0.4 Bcf Average Well Gas Production Rate 800 Mscf/day 300 Mscf/day 625 Mscf/day 180 Mscf/day Bbl, Barrel (42 gallons), bsl – below surface level

The San Juan Basin

The San Juan Basin covers an area of about 7,500 square miles located near the Four Corners region of Colorado, New Mexico, Arizona and Utah (Figure 16). The basin measures roughly 100 miles in length in the north-south direction and 90 miles in width.

The foremost coal-bearing unit in the basin is known as the Fruitland formation. CBM production occurs predominantly in coals of the Fruitland Formation, however, some CBM is held in the underlying and adjacent Pictured Cliffs sandstone, and numerous wells are completed in both zones. Individual coalbeds of the Fruitland Formation average from 20 to over 40 feet thick. The total net thickness of the coal beds ranges from 20 to over 80 feet across the basin.

The waters in parts of the Fruitland Formation usually contains less than 10,000 mg/L TDS. In the northern half of the formation, most water contains less than 3,000 mg/L, and wells near the outcrop produce water that contains less than 500 mg/L.

Typical CBM wells in the San Juan Basin range from 550 to 4,000 feet in depth, and about 2,550 such wells are currently operating (coccc and NM OCD, 2001). The San Juan Basin is the most productive CBM basin in North America. CBM production in the basin averages about 800 Mscf per day per well (Stevens et al., 1996).


Production began in the late 1980s and rapidly expanded through the 1990s but is no longer increasing. Companies are attempting to maintain production by focusing on enlarging gathering facilities, upgrading production equipment, installing pumping units and wellhead compression, recavitating producing wells, experimenting with secondary recovery efforts, and downspacing from 320-acre units to 160 acre spacing.

In 2000, the San Juan Basin produced 0.78 Tcf of gas, representing 4% of total U.S. natural gas production and 80% of the nation's CBM production. The BLM's recently completed EIS predicts that 12,500 new oil, gas, and CBM wells will be drilled in the San Juan Basin over the next 20 years. Infill drilling—drilling wells on reduced spacing requirements, at every 160 acres rather than 320 acres—has already begun.

 
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