Environmental Engineering Reference
In-Depth Information
Figure 2.2 US Coal Reserves, Locations
Western
Appalachian
Interior
Source: USEIA 2010.
exploration consists of gathering available information about an area from library sources,
state and local government agencies, previous mining activities, and oil, gas, and water well
records. This information will be used to prepare databases and preliminary maps of the area
showing seam depth, thickness, and structure. Reports and maps available on the Internet or
digital analysis of satellite imagery may be used (Upadhyay 2000). The second stage of coal
exploration is a site visit by field geologists. They verify data gathered during the first stage
and supplement it with measurements of any outcrops, samples from exposed coal seams, and
other physical evidence. The field team checks access to possible drill sites, local laws and
regulations concerning drilling, and ability of local infrastructure to support a drilling effort
(e.g., roads, accommodations, fuel).
After completion of the second stage and reevaluation of a location's potential, core drilling
and logging of boreholes provide detailed measurements of coal reserves and information on the
depth, structure, thickness, and quality of coal, the most important and costly stage of exploration.
Spacing of drill holes depends on the complexity of local geology, but for measured reserves is
typically 0.5 miles (Christman et al. 1980, 73). Drill hole cores provide detailed information on
mine roof and floor materials, as well as coal samples for quality analysis. A small percentage of
drill holes are cored top to bottom to provide detailed geochemical information on overburden
material. Core drilling is significantly more expensive than normal drilling, so methods have
been developed to provide the same information without coring, through use of various well log
tools, and digital down-hole data logging is increasingly common. Geophysical logs can provide
measurements of material density, clay content, and coal quality. After the drilling and logging
program is completed, detailed maps of coal structure, thickness, quality, and depth of burial are
produced (Upadhyay 2000). This data is easily converted to maps and reports (Hamilton 2005,
222-23). With this information, it is possible to decide whether the prospect area provides suf-
 
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