MICHIGAN ACADEMY OF SCIENCE. 
37 
THE OIL HORIZONS. 
From the data assembled before drilling began, it appeared that the 
Berea was the most promising horizon to test for oil and gas. At Bay 
City, there were strong signs just above the horizon and also, in the 
Blaekmar well, considerable gas was yielded from this formation. A 
favorable structure seemed to be the only thing lacking for an accumula- 
tion of commercial size. It was a keen disappointment when the Berea 
in most of the wells yielded only a small quantity of gas, which, however, 
increased considerably with time. In some wells, the gas was not noticed 
for some time after the Berea brine was cased off. The latter, though 
apparently very strong was also deficient in quantity, — there never being 
a flow of much more than about 30 barrels per day. For some time, 
it was a puzzle why this formation did not yield a greater abundance 
of brine, as it was so thick and well represented. An examination of 
the samples showed that the Berea is a very fine and close grained gray 
to white sandstone. In some phases, the sand grains are too fine to be 
readily distinguished by the naked eye. It is this fine to exceedingly 
fine grain of the rock which not only limits the flow of brine but also 
that of the gas. A heavy charge of nitro glycerine might possibly loosen 
up the rock enough so that a considerable flow of gas could be obtained 
from the Watson well or from some of the other wells. The head of 
brine might overpower it, however. 
The so-called “Saginaw Sand” appears to be a sandy or clierty lime- 
stone. There seems to be some doubt as to the exact nature of the oil 
horizon, but all of the samples examined by the writer have proved to be 
true limestones though often clierty or sandy, effervescing very vigorously 
and leaving a comparatively small residue of sand and chert. At any 
rate, the “sand” is thin and pinches out wholly to the southwest in the 
Jackson-Church well. In the Cresswell or No. 4 well, the sand was 
represented by two sands,- — that is, two clierty limestones separated by a 
shaly layer. In the Watson well, there was a cherty or sandy pyritous 
limestone filled with black micaceous particles from 2325 to 3469 feet. 
The Dundee oil horizon appears to be some 35 feet below the top of the 
formation and is a light gray to buff and brown granular limestone 
effervescing violently with dilute hydrochloric acid. A fragment of the 
limestone shot out of the Jackson-Church well was a gray granular 
porous limestone, the pores being readily seen by the naked eye. The 
oil horizon appears to be free from water, but, lower down at no great 
depth, there is an abundance as shown in the Jackson-Church. the Wat- 
son. and the Green Point wells. 
EXPLORATION. 
Of the eight wells now completed in the Saginaw field, including Mr. 
C. McClure’s Gera well, only three (Nos. 2, 3 and 4) appear to be on 
the anticline and these three, perhaps significantly, yield oil and gas in 
considerable even if not commercially important quantities at two differ- 
ent horizons. The Cresswell hole showed four oil producing horizons. 
The other wells were all located from about half to three or four miles 
distant from the apparent crest of the anticline and made little or 
no showing of either oil or gas. The Watson or No. 5 perhaps may be 
excepted as this well yielded considerable gas at the Berea horizon. This 
