Deep-coal-bed methane potential of the San Juan River coal region, southwestern Colorado
The deepest, highest ranking and probably gassiest coals in the San Juan River coal region of southwestern Colorado are found in the 100 mile (mi) wide San Juan Basin of Colorado and New Mexico. The thickest and most continuous coal beds in the basin are found in the Cretaceous Fruitland Formation. Logs from 231 petroleum exploration drill holes were used to produce the following: a Fruitland Formation isopach, a Pictured Cliffs structure map, Fruitland Formation net coal and net sand isopachs, and Fruitland coal percentage and sand percentage maps. Of the 231 holes, 8 produced natural gas from sandstones in coal bearing zones, 5 were production tested in mixed sandstone and coal intervals (one well had an initial production of 1.6 MMCFGPD), and 5 were drill stem tested in coal bearing zones (one flowed 1 MMCFG in 35 min). The authors calculate 19.7 billion tons of coal are present in the study area. The coals are ranked high-volatile B (hvB) and high-volatile A (hvA) with local upgrading to medium-volatile (mv). Comparing gas contents of Cretaceous Raton Mesa coals to San Juan Basin coals, a gas potential ranging from 72 cubic feet/ton (cu ft/ton) to 514 cu ft/ton exists. The authors estimate a gas resource in the study area ranging from 1.4 to 10.0 trillion cubic feet. The data indicates that gas is present in the coals of the study area. This gas has been produced from sandstones adjacent to the coals and possibly from the coals themselves. Therefore, it might pay to test the Fruitland coals encountered while drilling for deeper targets. With the right economic factors and development of completion techniques for coal bed methane, this gas resource may prove to be important. Data gained from vitrinite reflectance of cuttings, desorption of cuttings, and desorption of conventional cores continue to support the existing evidence that coal bed gas is being generated and trapped in the deeper portion of the San Juan Basin.
- Research Organization:
- Colorado Geological Survey, Denver (USA)
- DOE Contract Number:
- FG21-80MC14256
- OSTI ID:
- 6333496
- Report Number(s):
- USGS-OFR-80-2; ON: DE83010377
- Resource Relation:
- Other Information: Portions are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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Geology and fuel resources of the Fruitland Formation and Kirtland shale of the San Juan Basin, New Mexico and Colorado
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