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STATE OF ILLINOIS

ADLAI E. STEVENSON, Governor

DEPARTMENT OF REGISTRATION AND EDUCATION

NOBLE J. PUFFER, Director

DIVISION OF THE

S TAT E GEOLOGICAL SURVEY

M. M. LEIGHTON, Chief
URBANA

CIRCULAR No. 151

COAL RESOURCES OF FRANKLIN COUNTY, ILLINOIS

GILBERT H. CADY

OIL ACCUMULATION IN THE CYPRESS SANDSTONE IN THE
HERALD POOL, WHITE AND GALLATIN COUNTIES, ILLINOIS

NANCY McDURMITT

ILLINOIS GEOLOGIC^

SURVEY" ! lOR/V^Y

MAY 28 1986

PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS

URBANA, ILLINOIS
1949

3 305

00004

6148

Illinois Academy of Science Transactions, Vol. 41, 1948 65

GEOLOGY

COAL RESOURCES OF FRANKLIN COUNTY, ILLINOIS*

GILBERT H. CADY
State Geological Survey, Urbana

Franklin County, Illinois, is
unique as a coal producing area in
several ways : It is the only .coal
producing county in the State which
at the start of the century had pro-
duced no coal and contained no coal
mines. In 1946, however, this county
produced more coal than any other
county in the State — 14,470,904 tons
or 23 percent of the total State pro-
duction for that year. Its average
production per mine in 1946 of
1,113,146 tons was exceeded only by
Christian County where five mines
produced an average of 1,279,882
tons. One mine in Franklin County
attained the highest output in the
State of 2,469,470 tons, a relative
position which this mine has held
for 8 years and for 20 out of 22
years prior to 1947. This same mine
also holds the daily output record
of the State of about 15,000 tons, a
record, however, which was nearly
equalled by a rival mine in the
county. It had the fame, at one time
at least, of being the world's largest
underground coal mine. Production
in Franklin County is at present in
the hands of five operating compa-
nies, one mine being a captive mine
owned by a railroad which takes all
its production.

Franklin County originally con-
tained what appears to have been
the State's largest volume of coal
with a sulphur content of less than
1.25. A considerable part 'of this
coal contained less than 1 percent
sulphur. It also contains the State's

thickest known bed of coal, which is
9 to 14 feet thick over considerable
areas. Franklin County has prob-
ably been more thoroughly explored
by the diamond drill than any other
county in the State, but exploration
lias not often extended below No. 5
coal bed, only thirteen holes having
been drilled to the greater depth,
out of more than 300 that have been
drilled.

The coal mined in Franklin
County is produced by fewer men
per ton — 8.7 tons per man day in
1946 — than that produced by any
other county in the State except
Christian which had a rating of 11.5
tons per man day for the same year.
The 1946 record in neighboring
Saline County, in spite of the con-
siderable strip-mine tonnage, was 6.5
tons per man day, and for Macoupin
County 7.6 tons. Fulton County, on
the other hand, where most of the
coal comes from strip mines pro-
duced coal in 1946 at the rate of
21.22 tons per man day.

Many more persons are employed
in the coal industry in Franklin
County mines than in any other
county of the State, 7,402 employees
being reported for 1946. The county
with the next largest mine pay roll
is Macoupin with 2,693 employees.

Eailroads conveying coal out of
Franklin County derive an annual
revenue of about 20 million dollars
from this service, assuming an aver-
age freight payment of $2.00 per
ton. In 1946 about 10 million tons
of coal were shipped on four rail-
roads serving the county, requiring

Illinois Academy of Science Transactions

200,000 fifty-ton cars, or 4,000 fifty-
car trains, or an average of more
than 10 such train-loads daily dur-
ing 1946.

The fatality record of the mines
in Franklin County has fallen from
the high rate of 4.89 fatalities per
million tons of coal produced be-
tween 1911 and 1919 to an average
of 1.11 fatalities per million tons
between 1940 and 1946. This de-
cline, although still higher than the
State average of 0.4 in 1946, which
is unusually low, has been brought
about in spite of a highly hazardous,
natural gassy condition in these
mines, largely owing to the contribu-
tions to mine safety made by one
of the foremost mine safety engi-
neers in the country and a notable
citizen of the county, John E. Jones.
The present methods of mine rock
dusting in widespread use through-
out the country are largely due to
Mr. Jones' ingenuity and persist-
ence.

Over against the numerous facts
pointing to the great importance of
the coal mining industry and the
coal resources to this region are

other facts that call for the evalu-
ation of the permanence of this in-
dustry and the availability of the
coal resources. To what extent are
these resources actual' reserves of
wealth and prosperity?

The area of the county is rela-
tively small. This is the 66th county
in respect to size, having an area of
445 square miles (284,716 acres).
Furthermore, in about 14 percent of
the area or 60% square miles (38,-
685 acres) the No. 6 coal bed is re-
garded as unworkable because the
bed splits into unmineable thin
parts. This leaves 384% square
miles (246,031 acres) of the county
underlain by workable No. 6 coal
bed, assuming that a bed less than
6 feet in thickness at depths varying
from about 750 to 850 feet is work-
able.

There is the further consideration
that vigorous mining has been un-
derway in this county about 45
years with a total output to the end
of 1946 of 399,794,122 tons.

The original supply of coal in the
No. 6 coal bed has been estimated on

Table 1. — Original Coal Resources in No. 6 Coal Bed in Franklj

Area in
acres

Percent

of
county

Percent

of
produc-
tive

Estimate

1916

Coop. Bull

Estimate
1934

Estimate
1948

Percent

Millions of tons

Split coal area

Coal more than 8 ft.

thick (Av. 9 ft.

assumed)

Coal 6-8 ft. thick

(Av. 7 ft. as-

38,685
113,970
92,162
39,962

14
40
32
14

47
37
16

1,814

1,142

424

Coal under 6 ft.
(Av. 6 ft. as-

Total

284,716

3,718

3.282

3,381

Coal Resources of Franklin County

various bases from time to time
(table 1) and appears to be about
3 1/3 billion tons, of which 424 mil-
lion tons or 12 percent is probably
less than 6 feet thick, 1,142 million
tons or 34 percent is between 6 and
8 feet thick, and 1,814 million tons
or 54 percent was more than 8 feet
thick.

A total of 30 percent of the area
underlain by No. 6 coal bed in the
county, exclusive of the split-coal
area (table 2) (73,454 acres or 114.8
square miles) has been mined out or
rendered unmineable (fig. 1) and
this area contains essentially all the
coal with less than 1 percent sulphur
content and much of that with less
than 1.25 percent sulphur.

Most of the remaining supply of
No. 6 coal bed lies in the eastern
half of the county, and only two of
the existing mines are probably so
situated that they can mine the coal
in this area within reasonable limits
of cost. It is also significant that
several mining ventures in the
northeast part of the county north
of or along the Illinois Central Rail-
road from Benton southeastward,
found it impossible to maintain pro-

duction in competition with the
more favorable conditions in the
mines in the western part of the
county.

In spite of the evident realiza-
tion on the part of the coal mining
industry of the approaching deple-
tion of the better and thicker por-
tions of No. 6 coal bed in the western
side of the county, no new mining
ventures, as indicated by advanced
drilling, seem to be underway in the
northeastern part of the county.

In this connection attention may
well be called to what appears to be
an area of relatively thick coal north
of Logan and in the vicinity of Bes-
sie in an area traversed almost down
the center by a branch of the Illinois
Central Railroad running from the
vicinity of Akin to West Frankfort
(fig. 1). The position of the area
is also indicated on Fig. 2 as an area
where the thickness of the interval
between the No. 6 coal and the first
limestone is more than 10 feet. Addi-
tional drilling is necessary to prove
the area but it seems to hold promise
of being the only tract north of the
Illinois Central Railroad branch to
Eldorado in eastern Franklin Coun-

Table 2

-Data c

• Depletion of No. 6 Coal Bed in Franklin County

Acres Sq. Miles

Total mineable area 246,013 384.4

(Excluding split coal: 14% of county)
Mined out area:

A. Actual (25%) 61,649 98.3

B. Including barriers (30%) 73,454 114.8

Total production in tons (to date of mine maps) 385,401,214 tons

Production in tons per acre:

A. Actual mined-out area 6,252 tons

B. Including barriers 5,247 tons

Thickness of coal removed (in feet) :

A. Actual mined-out area 3.53 feet

B. Including barriers 2.96 feet

Percentage of coal removed:

A. Actual mined-out area

1. 9 ft. assumed average thickness 39 percent

2. 8% ft. assumed average thickness 42 percent

B. Including barriers

1. 9 ft. assumed average thickness 33 percent

2. 8% ft. assumed average thickness 35 percent

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Fig. 1. — Map of Franklin County showing mined-out areas, "cut-out" area,
areas in which sulphur content of No. 6 coal bed is less than 1.0 percent, between
1.0 and 1.25 percent, and greater than 1.25 percent; and areas in which No. 6
coal bed is less than 6 feet, between 6 and 8 feet, and more than 8 feet thick.

ty where there are attractive possi-
bilities from the viewpoint of pres-
ent mining requirements.

In connection with the depletion
of resources in No. 6 coal bed in
western Franklin County the char-
acter of recovery is of interest. The
prevailing idea concerning the re-
covery as expressed by most engi-
neers in the area is that this amounts
to about 7,000 tons per acre. Assum-
ing a weight for the coal of 1770
tons per acre foot (a figure long used
by the State Geological Survey in
coal resource studies) the recovery
is equivalent to a bed almost exactly
4 feet thick (7080 tons). This re-
covery has been in an area where the
thickness of the No. 6 bed exceeds
eight feet and not infrequently is
10 feet. It seems, therefore, even on
the basis of the commonly accepted

figure of 7,000 tons per acre that the
recovery is less than 50 percent.

Planimeter measurements of the
mined-out area indicated on a small
scale map (fig. 1) show that the
total production of 385,401,214 tons
(up to the date of the mine maps)
had been taken from a mined-out
area of 61,650 acres. This represents
an average recovery of about 6,250
tons per acre (table 2), rather than
7,000 tons.

Recovery is not uniform in differ-
ent parts of the county. Consider
the three separate, more or less in-
dividually continuous areas, one in
the south part of the county, one
in the north part (but not including
the detached mines near Sesser),
and one in the eastern part (but
not including the mine at Logan).
The recovery (table 3) in the mined-

Coal Resources of Franklin Comity

Fig. 2. — Map of Franklin County showing the distribution of variations in the
interval between No. '6 coal bed and the first limestone above this coal bed, (10, 25,
50, and 100 feet) and the location of diamond-drill holes extending below No. 5
coal bed.

Total

production in

thousands

Production

in tons per

acre

North Tract
Actual mined-out area. .
Including barriers

South Tract
Actual mined-out area . .
Including barriers

East Tract
Actual mined-out area. .
Including barriers

Illinois Academy of Science Transactions

out southern part is at the rate of
3.64 feet, in the northern tract es-
sentially the same, but in the east-
ern area is only 2.86. These figures
refer only to the actual mined-out
area as bounded by the extreme face.
If the total area is considered, bar-
rier pillars, town site reserves, rail-
road right-of-way pillars and un-
mined irregularities such as those
along the margin of the split coal
area, the figures are smaller, being
3.12 feet for the southern area, 2.98
for the northern area, and 1.77 feet
for the eastern area where abandon-
ment of the mines will undoubtedly
result in high barrier-pillar loss mar-
ginal to any new operations.

The character and thickness of
the No. 6 coal bed bears a definite
although not fully understood rela-
tionship to the black shale and lime-
stone caprock. Wherever the coal
bed is separated from the black
shale by less than about 10 feet of
strata (usually by gray shale) the
coal bed is rarely more than about
8 feet thick and commonly not more
than 6 feet thick. The thin coal bed
is characterized by a high sulphur
content, usually more than 2 per-
cent. The critical relationship, how-
ever, is not that of thickness of bed
but one apparently involving the
proximity of the black shale. Be-
cause of this very definite and well
substantiated relationship it seems
probable that the thin No. 6 coal
bed in the eastern and northeastern
part of the county, where the black
shale and limestone lie close above
the coal bed, will have a relatively
high sulphur content from which it
will probably be difficult but per-
haps not impossible to produce the
same high quality fuel as has been
shipped out of Franklin County for
many years.

There is at least one other matter
that affects the volume of coal re-
serves to some extent. It is regarded
as good practice to guard oil test

holes by at least a 100-foot pillar,
that is by a pillar not less than 200
feet in diameter. Where pools have
developed in a mining area the
mines and position of the drill holes
are usually so planned as to reduce
to a minimum the extra loss involved
in an oversize pillar for an oil well
or test hole. Where wells are drilled
in abandoned mines or abandoned
parts of mines no extra loss of coal
is involved unless the well or wells
get out of hand in the mine and
cause disruption of mining and loss
of coal or even of the mine. In the
case of wildcat wells or drill-holes
or where pools consist of only a few
wells some loss of coal may be ex-
pected, particularly if uncertainty
exists in regard to the character of
the plugging. In such a case it is
advisable to provide a 200-foot
rather than a 100-foot pillar around
the drill-hole. A 100-foot pillar con-
tains about 1277 tons per foot of coal
or about 10,000 tons for an 8-foot
bed. A 200-foot pillar would contain
about three times as much. There
are, up to date, in the order of 75 to
100 oil test holes in the largely un-
developed eastern half of the county
(fig. 3).

Brief consideration may now be
given to the resources present in
Franklin County in beds other than
No. 6. Of these coal No. 5 (fig. 4)
which lies from 30 to about 100 feet
below coal No. 6 is the most impor-
tant and most widespread. Its con-
tinuity is probably somewhat greater
than that of No. 6 since it appears
to be present under at least part of
the "split-coal" area although to
what extent is not well known. In
general No. 5 bed is 3 to 4 feet thick,
and fairly uniform in thickness. In
the north part of the county there
is one area where the bed is 5 feet
thick, being nearly as thick as the
No. 6 bed. The number of drill-holes
that have penetrated to No. 5 bed
is too small and the holes are too

Coal Resources of Franklin County

erratically distributed to justify
statements as definite in regard to
the quantity of coal present in this
bed as can be made in regard to No.
6 coal bed. There is particular need
for more information in the north-
east part of the county and in the
"split-coal" area.

As a coal reserve, in the sense of
a body of recoverable coal under
prevailing mining conditions, the
No. 5 bed has uncertain and rather
doubtful value. It is very doubtful
whether it can be recovered where
it lies below areas of mined out No.
6 bed, particularly where the inter-
val is less than about 50 feet. Un-
less mining conditions change con-
siderably, and this possibility of
course exists, the value of No. 5 coal

bed as a real reserve rates low. How-
ever, in those parts of the county
where the No. 6 and No. 5 bed lie
75 to 100 feet apart mining meth-
ods may be devised, as new machines
become available, so that both beds
can be recovered simultaneously. It
seems reasonable to regard as pos-
sible the recovery of as high a pro-
portion of the combined 10 feet of
coal in the two beds as has been
recovered from the single bed of the
same thickness in western Franklin
County. There are possibilities of
improved rec.overy in the retreating
method of mining that have not been
explored but deserve trial. In any
case, however, the No. 5 coal bed will
probably not supply the natural
premium quality of coal character-

Illinois Academy of Science Transactions

'interval to no.6 bed

'• -40'

|* 40'-50'

A 50'- 75'

» +75'

Fig. 4. — Map showing drill-holes that have penetra
of variation in the thickness of the No. 5 bed, and the
tween No. 5 and No. 6 beds.

istic of the No. 6 bed where it is now
being mined.

The amount of coal represented
by the No. 5 coal bed in Franklin
County, assuming that there are 309
square miles in which the bed aver-
ages 3% feet thick (3 to 4 feet), 125
square miles in which it averages
4^ feet (4 to 5 feet) and 11 square
miles in which it averages 5 feet (5
feet plus) is as follows:

Thickness Square

Feet Miles Tons

3% 309 1,225,123,200

4% 125 642,297,600

5 11 63,304,000

Total 1,929,724,800

or roughly 2 billion tons. Of this
704,601,600 tons represent the coal
bed where it is more than 4 feet
thick. Of this area 60 square miles,

in which there are 310,953,000 tons
of coal, is in the area where No. 6
bed has already been mined out and
the possibility of recovery of No. 5
coal is regarded by the writer as
doubtful. This leaves about 400 mil-
lion tons of coal thicker than 4 feet
in the area where No. 6 coal has not
yet been removed. Of this probably
no more than about 200 million tons
is recoverable, unless mining meth-
ods change considerably, which is
possible.

In view of the very little informa-
tion in regard to the thickness of
No. 5 coal bed in the northeastern
part of the county these estimates
are based on an assumed thickness
of 2>y<2, feet. This estimate involves
the resources in this bed for about
one-quarter of the area of the
county. It may be hoped that fur-

Coal Resources of Franklin County

REPRESENTATIVE LOGS SHOWING COAL BEDS BELOW HERRIN
NO. 6 COAL IN FRANKLIN COUNTY

ther drilling may find that this
estimate is too conservative.

The coal resources of the county
are not completely represented by
the No. 5 and No. 6 coal beds. There
are no beds exceeding about 18
inches in thickness above the No. 6
bed. The Cutler coal bed, commonly
present 30 to 40 feet above the Her-
rin (caprock) limestone may occa-
sionally reach 2 feet, but it is
lenticular and generally unmineable.
The accompanying chart (fig. 5)
shows the position and thicknesses of
coal beds below No. 6 bed in a group
of diamond-drill holes that have
been rather recently drilled here
and there in the county. The amount
of such deep drilling has been rela-
tively small (fig. 2) and not scat-
tered widely enough to provide a
very satisfactory picture of the

areal extent of the deep lying beds.
The general conclusion that can be
derived from the available informa-
tion is that although occasionally
coal beds 4 to 5 feet thick may be
present and be penetrated in drilling,
the beds are usually not thick and
are characteristically lenticular and
discontinuous. The two beds believed
to have the widest distribution are
known as the DeKoven and Davis
lying between 250 and 300 feet be-
low No. 6 bed. Even these are thin
and become difficult to recognize
toward the west, and even on the
east side of the county are not likely
to be more than 40 inches thick. The
DeKoven, the upper bed of the two,
is likely to be " cut out ' ' by the over-
lying Palzo sandstone. The well
known Murphysboro coal bed of
Jackson County has not been recog-

Illinois Academy of Science Transactions

nized with certainty among the coal
beds penetrated in Franklin County.
It may be either the Stonefort or
Bald Hill bed. It is not the DeKoven
and Davis bed as was once thought.

It is not probable that these lower
coal beds will ever provide a basis
for large coal mining industry such
as that with which we are now famil-
iar in Franklin County, although it
cannot be said that none of these
beds will ever be mined. Further
drilling may discover considerable
areas where one or more of these
beds maintains a thickness of 4 to 5
feet. Furthermore, "ever" is a long
time and man may get very des-
perate for fuel.

Underground gasification holds
some possibility for utilizing the
energy present in the thinner coal
beds and in portions of the thicker
beds where the quality is poor, such
as in the split portions of the No. 6
coal bed. Once the No. 6 bed is en-
tirely worked out adjacent to the
"split-coal" area the development
of gasification projects as a means
of recovering the energy available in
the split portions of the bed is a pos-
sibility that should not be over-
looked. The same procedure might
be applied to No. 5 and lower beds
where conditions might be suitable.
It is very desirable that under-
ground gasification be tried under
conditions existing in the coal fields
of the middle west in order to pro-
vide a satisfactory basis for deter-
mining its applicability to these coal
beds.

Conclusion

The coal resources of Franklin
County may be classified into four
categories : First, those resources
which represent coal which can be
and probably will be recovered un-
der present conditions of mining
practice and competition, the cer-

tain reserves ; second, those resources
represented by coal 6 to 8 feet thick
which probably will be recovered,
the probable reserves; third, those
resources represented by a coal bed
less than 6 feet thick concerning
which the possibilities are doubtful,
the doubtful reserves; and, finally,
those resources represented by beds
too thin or irregular, or both, that
probably never will be worked and
therefore cannot be regarded as re-
serves of energy or wealth.

The definite or certain reserves
are represented by ' the approxi-
mately 897 million tons of coal in
a bed 8 feet or more thick. The coal
in this reserve is held very largely
by two companies with a present
combined output of about 10 mil-
lion tons. By maintaining an un-
usually high rate of recovery of
about 55 percent at the same an-
nual rate of production this body
of coal should last another fifty
years. It is not to be expected,
however, that the man power re-
quired to mine this volume of coal
will continue at the present rate
but that it will decrease. According-
ly the mine pay-roll in the county
will undoubtedly fall from year to
year partly because of the complete
depletion of some of the mines and
as a result of more efficient recov-
ery in terms of tons per man day.
A stepping up of the production by
these two mining companies would
of course tend to maintain pay-roll
volume, but would shorten the life
of the field.

The second category of reserves
is represented by No. 6 bed where
it is between 6 and 8 feet thick and
by No. 5 bed where it is more than
4 feet thick. Consider No. 6 coal
bed first: The probability of min-
ing in this area containing approxi-
mately a billion and one-quarter
tons of coal is affected by the ab-
sence of operating mines and the

Coal Resources of Franklin County

more important unprofitable ex-
perience of companies that have un-
dertaken such mining in the past.
In general this intermediate area of
the No. 6 coal bed is intermediate
in other ways than in geographical
position. The coal is characterized
by considerable variability in qual-
ity and thickness, the sulphur con-
tent varying in short distances from
relatively low to relatively high.
The roof conditions provide a haz-
ard that mining companies will
hesitate to face. The interval be-
tween the coal bed and the caprock
varies irregularly with lenticular
bodies of gray shale commonly in-
tervening between the coal bed and
the black shale that usually lies im-
mediately below the caprock. Cost
of development will be increased by
the need for more than the usual
number of holes in order that ir-
regularities may be sufficiently ex-
plored. Successful operation, of this
6 to 8-foot coal bed also calls for
more technical study of the roof
material than has yet been applied
to such rock, but considerable and
possibly the best information about
conditions in the area will be ob-
tained as the mines operating in
the more favored reserve area ap-
proach the margin of that area and
encounter thinner coal and more
irregular roof conditions. For the
present at least it appears that the
area of 6 to 8-foot coal should be
written off as an immediate reserve,
but the general thickness of the coal
is such that a few improvements
in mining or cleaning practice, or
both, might very well throw it into
the category of the immediate re-
serve.

With respect to No. 5 coal bed :
The coal present in this bed lies in
either the probable or doubtful re-
serves. The portion of the bed con-
cerning which there is undoubtedly
the most interest is where the bed
underlies the already worked out

areas of No. 6 bed because it can be
reached so easily from shafts now
working in the upper bed. Some
of these shafts actually extend to
the No. 5 bed already. It would
seem as though the No. 5 bed could
be worked as cheaply while opera-
tions are still active in No. 6 as
after such operations cease, and
failure to start such operations up
to the present is not an encouraging
indication of the workability of the
bed.

The area of greatest promise with
respect to No. 5 bed appears to be
the approximately 11 square miles
in the northern part of the county
where the bed is more than 5 feet
thick. It would seem desirable if
the coal should be explored in this
tract to mine both No. 6 and No. 5
beds from the same shaft. The
two beds are sufficiently widely
spaced and the lower coal sufficient-
ly thick so that it might be possible
to work the lower and upper beds
contemporaneously in a large area
in the southeastern part of the
county where No. 6 coal is over 6
feet thick.

In the northeast part of the coun-
ty where No. 6 coal is less than 6
feet thick both beds are 800 feet
or more in depth and the coal re-
sources in both beds rate no bet-
ter than doubtful reserves al-
though there has not been enough
drilling for definite estimates.

The coal present in the beds be-
low No. 5 coal represents a doubtful
reserve. Drilling to date does not
provide information sufficient to
justify including such coal beds
that have been encountered in
either of the high categories. In
certain areas there seem to be lenti-
cular fairly thick bodies of one or
more of the coal beds below coal
No. 5 but no two holes seem to have
penetrated coal beds as much as
four feet thick at the same strati-
graphic position except possibly in

Illinois Academy of Science Transactions

the case of the Davis coal. This
bed seems to be that thick only in
the southeastern part of the coun-
ty. It is possible that some time
one or more of these beds might be
found suitable for underground
gasification, but it is not probable
that they will be mined by shafts,
except possibly in very local areas.
The present study of the status
of coal resources and coal reserves
in Franklin County points to the
complete exhaustion of the high
quality more easily mined No. 6
coal within the county in a matter
of about 50 years or less. This
depletion of No. 6 coal where it
is more than 8 feet thick will un-
doubtedly be accompanied by the
gradual decrease in the number of
individuals supported by the min-
ing industry in the county. It is
quite possible that this decrease

may take place slowly enough to
cause no particular hardship.
Furthermore, there is a possibility
that some of the slack, should any
exist, may be taken up by the start
of new operations in the coal lands
underlain by No. 6 bed where it is
between 6 and 8 feet thick. This
possibility depends a good deal
upon progress made in mining
methods, in improved efficiency of
mining machines, in the improved
understanding of the behavior of
roof materials, and on improve-
ments in mechanical devices for
converting the energy in the coal
into mechanical energy. Encour-
agement must be given to coal re-
search in fields, such as geology,
chemistry, and various branches of
engineering impinging upon the
coal mining industry and various
aspects of coal utilization, includ-
ing underground gasification.

Summary of Resource Data foe No. 6 Coal Bed in Franklin County

The area of the county

The "split-coal" area

Area exclusive of "split-coal" area

Area in which No. 6 coal bed has been mined or rendered un-

mineable

Total area No. 6 coal bed unavailable either mined out or in

"split-coal" area

The available balance

Of the available balance area (100%)

No. 6 coal is less than 6 feet thick in

No. 6 coal is 6-8 feet thick, excluding mined out area, in. .
The remaining area No. 6 more than 8 ft

Acres

284,716
38,685
246,031

73,454

Square

445

60.5
384.5

114.8

175.2

62.4
141.2
66.0

Converted into tonnages these data signify that

The area of No. 6 less than 6 feet thick contains 424,396,000 tons

The area of No. 6 between 6 and 8 feet thick contains 1,125,887,000 tons

The area of No. 6 in which No. 6 coal is more than 8 feet

thick, contains 896,917,000 tons

No. 5 Coal Bed

The coal in No. 5 coal bed in Franklin County is approximately 2,000,000,000
tons. It ranges from a possible to a doubtful reserve.

Illinois Academy of Science Transactions, Vol. 41, 1948

OIL ACCUMULATION IN THE CYPRESS SANDSTONE

IN THE HERALD POOL, WHITE AND GALLATIN

COUNTIES, ILLINOIS*

NANCY McDURMITT
State Geological Survey, Vrbana

Introduction

The Herald pool is located in
White and Gallatin counties in
southern Illinois (fig. 1). The pool
covers an area of approximately
1600 acres. Since its discovery in
1940, a total of 130 producing wells
have been completed, of which 651
have produced oil from the Cypress
sandstone. This sandstone has been
chosen for study, and the discus-
tion following is confined to it.

The Cypress is one of the lower
formations of the Chester series.
In the Herald pool area it consists
of three sandstones, commonly with
interbedded shales. The two lower
sandstones are thick and fairly con-
sistent, and sometimes separated
by thin shale. It is the upper sandy
zone which is productive in the
Herald pool. It is an extremely
variable zone of shale, sandy shale,
and sandstone. The sandstone
ranges from a tightly cemented
sandstone to a clean permeable
quartz sandstone, which is the pay
zone. Normally the sandstone is
overlain by shale or shaly sand-
stone. Occasionally the whole up-
per zone becomes a shale or shaly
sandstone. In places there is no
shale above the sandstone, so that
it is directly overlain by the Bar-
low limestone. However, in most
cases, it is the shaly layer over the
pay zone which forms the eaprock.

'Sees. 27, :«, 34, S,'.,— 6S-9E ; Sees. 2, 3, 4, 10,
11, 14, 15, 22, 23,— 7S-9E.
Includes three wells producing from other forma-

Structure

The Herald pool is in the south-
ern part of the Illinois basin. The
structure of the pool consists of
three "highs," with a general north-
south trend. Figure 1 shows struc-
ture contours on the base of the Bar-
low limestone, that is the top of the
Cypress formation. In general the
Cypress production is controlled by
these features. The northernmost
anticline is the largest of the three
and has on it the largest number of
wells.

Figure 2, (sec. 3, T. 7 S., R. 9 E.)
shows oil accumulation in a simple
structural trap. The wells high on
the structure produce oil and
water; those low on the structure
are dry holes, often producing
water with possible shows of oil.
The closure of the pay is about 6
feet.

The strata in the southern part
of the pool are cut by a fault or
fault zone, which strikes north and
northeast and dips eastward about
50° to 65°. The fault there cuts
a structural high on the Cypress.
On the upthrown side — the west
side — the pay dips westward from
the fault (fig. 3, sees. 22, 23, T. 7 S.,
R. 9 E.). Several wells produce oil
near the fault. It is probable that
the trap is sealed by an impervious
bed on the opposite face of the
fault which is in contact with the
pay.

Depositional Variations

Although the Cypress production
in the pool is generally controlled

Illinois Academy of Science Transactions

GEOLOGICAL SURVEY

—Structure map of the Herald pool. Locations of cross-sections are shown
by straight lines. Index map of Illinois shows location of the pool.

Oil Accumulation in Cypress Sandstone

I, ^ -t ■mrum ^r

3-T5-9E

— A-A', cross-section of a
structural trap.

cut by fault.

by structure, conspicuous devia-
tions of the production pattern
from the structure pattern indicate
the presence of another significant
factor — depositional variations.

The shaly zone above the pay is
of variable thickness. Changes in
its thickness accentuate or nullify
the effect of structure in forming
traps. If the shale interval is fairly
constant, the pay is high where the
structure is high — as in the struc-
tural trap shown in figure 2. If the
shale thins where structure is low,
the pay there may be high. In sec.
3, T. 7 S., R. 9 E. (figure 4) such
variation of shale thickness is suf-
ficient to form a trap where the
structure is low. Producers are
structurally low, dry holes that pro-
duce water are structurally high.

Another important depositional
variation is a change in the per-
meability of the pay. The sand-
stone may become shaly or inter-
bedded with numerous thin shale
streaks; commonly the interstitial

spaces of the sandstone are filled
with siliceous cement ; in sandstone
that is poorly sorted, the smaller
grains fill the spaces between the
larger ones ; the sandstone may
be lenticular. Such permeability
changes are typical of Illinois "oil
sands," where lateral variation of
beds occurs commonly within a few
acres, often within a few feet.

The distribution of producing
wells on the anticline in sec. 34,
T. 6 S., R. 9 E. is a striking illus-
tration of the effect of permeability
change, figure 5. There are many
producers on the northwest flank
of the anticline and several on the
crest. On the highest part of the
structure, however, are several dry
holes. Sample studies show the pay
in these wells to be shaly or cement-
ed. The tight zone, cutting across
the anticline, forms an effective seal
for the oil accumulated along the
flank of the structure.

3-C, cross-section showing ef-
fect of varying thickness of overlying
shale on the trap.

34-63-9E SE

D-D', cross-section of pay zone
sealed by tight zone.

Illinois Academy of Science Transactions

The small anticline in sees. 10
and 11, T. 7 S., R. 9 E. is a structure
almost completely dry because of
tightness of the sandstone. Only
one well produces on this structure.
The pay zone in the other holes on
the anticline, though high, is shaly.
The tested permeability of the sand-
stone in one of the highest wells
averages only twelve millidarcies.
Permeability of the pay in some
producers in the pool averages
eighty millidarcies.

These are primary features, re-
lated to conditions of deposition.
In contrast, the structural features
are the result of deformation.

Depositional variations on pro-
ducing structures account for a
number of dry holes throughout
the pool.

Summary

Production from the Cypress
sandstone in the Herald pool shows
the effect of both structural and
stratigraphic features on oil ac-
cumulation. There are examples
in the pool of oil in the Cypress
sandstone in the following types of
traps :

Simple structural trap.

Trap sealed by an impervious bed
at the fault contact.

Trap closed by thickening of over-
lying shale.

Trap sealed by a tight zone in the
pay across an anticline.

There are also examples of areas
high on structure which are dry
because of depositional variations:

Thickening of overlying shale.

Tightness of producing sandstone.

Oil Accumulation in Cypress Sandstone

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Full text of "Coal resources of Franklin County, Illinois"

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