subsurface geology and coal resources of the pennsylvanian system ...

Township
T. R.
1 N. 10 E.
IN. 11E.
1 N. 14 W.
2 N. 10 E.
2N. 14W.
1 S 10 E.
1 S. 11 E.
1 S. 14 W.
2 S. 10 E.
2 S. 11 E.
2 S. 14 W.
3 S. 10 E.
.3 S. 11 E.
3 S. 14 W.
Min.
545
570
545
541
542
559
525
526
528
556
548
558
555
5 27
EDWARDS
Intervals
Max. Av.
600 573
The average interval for the county is between
560 and 570 feet and is about the
same both north and south of the base line,
but with a slight tendency toward an increase
in interval toward the southwest.
Variations from the average are in the
order of about 40 feet, except for T. 3 S.,
R. 10 E., in which it is about 50 feet. In
spite of some difficulty in identifying the
exact position of the top of the Palzo
sandstone from electric logs, and of the
possibility of important variations in interval
between beds more than 600 feet apart,
the beds must be considered essentially
parallel.
WORKABLE COAL BEDS
In Edwards County the No. 5 and No.
6 coal beds should be protected from danger
of invasion by oil, gas, and water by properly
placed plugs when dry holes or oil wells
are abandoned. The No. 6 coal bed in the
317 drill holes tabulated lies at depths ranging
between 766 and 1029 feet. In only
16 holes was this coal bed found at depths
of 1000 feet or more. The No. 5 coal bed
lies at depths ranging between 886 and
1110 feet, with slightly more than half the
holes showing a depth more than 1000 feet.
Because in only one township, T. 2 S., R.
14 W., the interval between the No. 5 and
No. 6 coal beds exceeds 122 feet (table 6),
both beds can be protected by a plug extending
from 50 feet above to 175 feet below
No. 6 coal bed. This length of plug
is probably sufficient for most drill holes,
even in T. 2 S., R. 14 W. Indeed, a plug
extending from 50 feet above to 150 feet
COUNTY 6 3
below No. 6 coal bed will probably be adequate
to protect both coal beds in the majority
of drill holes.
The structure map of No. 6 coal bed
gives the altitude of the bed in feet below
sea level. If the hole to be plugged is on
or very near a structure contour, the depth
to the coal bed is obtained by adding to the
surface altitude the altitude shown on the
contour line. The altitude of the coal bed
at holes lying between structure contour
lines can be estimated by assuming an even
slope between the two nearest contour lines
through the position of the drill hole.
There is some indication of the presence
of coal beds 3$4 feet or more thick 300 to
400 feet below No. 6 bed. Evidence, however,
does not warrant recommendation of
their protection.
COAL RESOU RCES
In the first report of this series" it was
estimated, on the basis of information provided
by seven control drill holes, that the
coal resources of Edwards County represented
by No. 5 and No. 6 coal beds
a~nounted to about 1.2 billion tons. Since
that estimate was made six additional control
wells have been logged by Survey field
parties. The data now available in regard
to coal beds 3 feet or more thick are summarized
in table 7.
'No. 7" coal bed.-In six of the 13 control
drill holes the coal bed regarded as "No.
7" was reported as 3 feet thick. The bed
ranges from 26 to 83 feet above No. 6 coal
bed. It has a black shale cover 1 to 2 feet
thick, above which is a considerable thickness
of gray shale. The succession is quite
similar to that characteristic of the Danville
(No. 7) coal bed of Vermilion County,
Illinois, and to that of Indiana VII bed in
western Indiana. Although the bed is absent,
or at least not reported, in about half
the control drill holes, and the extent of
distribution must therefore be regarded as
uncertain, the presence of a coal bed or
some stratum that produces a similar pattern
at the appropriate position in the elec-
IG Cadv Gilbert H., Coal resources based upon inforrna-
,inn obtained from rotarv drilling Feb. 1 1942 to May
3 1. 1913 : Illinois Geol. Lrvey Rept. Inv. $3, p. 41, 1944.