Improved procedures for collection and interpretation of coal-gas reservoir gas content and natural fracture geometry data
- Resource Enterprises, Inc., Salt Lake City, UT (United States)
The validity of quantitative coal-gas reserve analyses depends upon the accuracy of formation evaluation data used as input parameters for reservoir simulation of fluid productivity. Coal-gas reservoir deliverability is strongly influenced by gas-in-place resources, natural fracture (cleat) permeability, and gas desorption and diffusion characteristics. Estimates of these parameters are predicted upon knowledge of coal core-gas content and cleat geometry. Ironically many accepted procedures for collecting and interpreting these data are still incomplete, and therefore coal-gas reserve analyses commonly are erroneous. Improved procedures for collecting and interpreting gas content and cleat geometry data are highlighted using eight Gas Research Institute Fruitland Formation (Upper Cretaceous) wells in the San Juan basin (Colorado and New Mexico). Fruitland gas content values, in places, have been underestimated by 30-85% (786 SCF ton vs. 122 to 557 SCF/ton, dry, mineral-matter-free basis), and therefore the corresponding gas-in-place resource estimates are commensurably conservative. Gas desorption measurements must be performed at reservoir temperature: dry, mineral-matter-free normalizations and canister headspace corrections must be performed correctly; and gas composition must be periodically quantified to correctly estimate the actual methane reserves and sorption time. Collection of cleat geometry data on whole cores is routinely biased because only the most apparent cleat systems are analyzed. Detailed macroscopic and X-ray radiograph data on cleat geometry for slabbed polished blocks should be collected as a function of bed thickness, lithology, and interconnectivity to further define core-scale cleat permeability and diffusion coefficient distributions.
- OSTI ID:
- 6701231
- Report Number(s):
- CONF-930947-; CODEN: AABUD2
- Journal Information:
- AAPG Bulletin (American Association of Petroleum Geologists); (United States), Vol. 77:8; Conference: Rocky Mountain section meeting of the American Association of Petroleum Geologists (AAPG), Salt Lake City, UT (United States), 12-15 Sep 1993; ISSN 0149-1423
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
01 COAL, LIGNITE, AND PEAT
COAL DEPOSITS
GEOLOGIC SURVEYS
NATURAL GAS DEPOSITS
GEOLOGIC FRACTURES
GEOLOGIC MODELS
LITHOLOGY
PERMEABILITY
GEOLOGIC DEPOSITS
GEOLOGIC STRUCTURES
GEOLOGY
MINERAL RESOURCES
PETROLOGY
RESOURCES
SURVEYS
030200* - Natural Gas- Reserves
Geology
& Exploration
011000 - Coal
Lignite
& Peat- Reserves
Geology
& Exploration