Overburden characterization and post-burn study of the North Knobs steeply dipping bed underground coal gasification (SDB-UCG) site, Rawlins, Wyoming

Technical Report · Sat Oct 01 04:00:00 EDT 1983

OSTI ID:6083332

Ethridge, F G; Saracino, A M; Burns, L K; Marks, T R; Youngberg, A D

The encompassing sandstones, siltstones, shales and thin conglomerates of the gasified G Coal seam at the North Knobs SDB-UCG site were deposited mainly in fluvial and poorly-drained swamp environments. These beds dip at 65/sup 0/ at the North Knobs site. Thin section and SEM analyses of the sandstones and coarse siltstones show that they are sublithic to subarkosic arenites cemented with clay minerals, calcite hematite, siderite and silica. The sandstones of Unit D directly above the coal seam have the highest concentration of calcite cement, the lowest mean grain size, and are best sorted in terms of quartz grain size variations; however, they are the worst sorted in terms of sieve size variations. Clay minerals in the sandstones are dominantly kaolinite and smectite with lesser amounts of illite and chlorite. These clays are of secondary origin. Heat alteration is present only in coals and overburden rock from cores that penetrated the cavity. Thermally altered rocks including hornfels, buchite, paralava rock and paralava breccia were found in the bottom of the dipping cavity near the injection well. The high temperature minerals of tridymite, cristobalite, mullite, cordierite, monoclinic pyroxene and high temperature plagioclase indicate that temperatures of at least 1200/sup 0/C to 1400/sup 0/C were attained in the lower part of the burn cavity. The mechanical test on the unaltered and altered overburden rock show that the most important lithologic property controlling rock strength and seismic wave velocity is the amount and type of cement in the rock. Other parameters measured were grain size, amount of clay cement, and porosity; sorting had a secondary effect on the rock strength and seismic wave velocity. There is a non-linear and direct relationship between mechanical strength and ultrasonic wave velocities for the rock tests. 30 references.

• Research Organization: Colorado State Univ., Fort Collins (USA); University of Wyoming Research Corp., Laramie (USA)
• DOE Contract Number: AS20-82LC10863
• OSTI ID: 6083332
• Report Number(s): DOE/LC/10863-T1; ON: DE84003756
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
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58 GEOSCIENCES
580300 -- Mineralogy
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& Rock Mechanics-- (-1989)
CAVITIES
COAL DEPOSITS
COAL GASIFICATION
COAL SEAMS
CONGLOMERATES
DATA
ELECTRON MICROSCOPY
EXPERIMENTAL DATA
FEDERAL REGION VIII
FIELD TESTS
GASIFICATION
GEOLOGIC DEPOSITS
HIGH TEMPERATURE
IN-SITU GASIFICATION
IN-SITU PROCESSING
INFORMATION
LITHOLOGY
MECHANICAL PROPERTIES
MICROSCOPY
MINERAL RESOURCES
MINERALOGY
NORTH AMERICA
NUMERICAL DATA
OVERBURDEN
POROSITY
PROCESSING
RESOURCES
ROCKS
SANDSTONES
SCANNING ELECTRON MICROSCOPY
SEDIMENTARY ROCKS
SHALES
SILTSTONES
TEMPERATURE EFFECTS
TESTING
THERMOCHEMICAL PROCESSES
USA
WYOMING