New-York tribune., 1918-08-04

~ AN geologist always tell, after
careful geologic examination,
~ whether territory will produce
oil if drilled? He cannot, says
Donald F. Macdonald, in "Sinclair's
Magazine" While he can often be GER
tain Of negative results in a region of
unfavorable rock conditions, he can sell
dom be equally sure of positive results
even where the geologic factors are
favorable. In the examination of new
oil territory, according to Mr.. MacDon-
aid, himself geologist, field procedure
is about as follows:
'All the areas of volcanic, crystalline and
other rocks that cannot contain oil are
eliminated.
"The areas Of sedimentary rocks, partcu-
iarly If they are equivalent in geologic age
and general aspect to the rocks which pro-
duce oil in other regions, are examined in
detail. Other things being equal, beds rich
IN plant or animal remains are regarded as
more favorable than those containing no
trace Of fossils. 1t is considered good
indication also when the rock series con-
sists of relatively porous sandy beds (possi-
ole oil containers} overlaid by or inter-
bedded with less pervious shaley or clayey
beds seals covers for the oil contaners),
all Of favorable geologic character.
"seepages OF oil or gas where the porous
beds outcrop or in the general vicinity are
favorable evidence, but the absence of
seepages is not proof that commercial guam
titles OF oil do not exist in the rocks
"lf water is largely absent from the oil
bearing series Of beds oil may accumulate
in the synclines. Furthermore, too much
faith should not be put in the matter of
having ideal structure at the surface if the
geological conditions are otherwise favor
able, for lenses or even nat arches Of oil
bearing rocks may occur beneath surface
where the outcropping beds show no IA
vorable structure.
"All areas where the rocks of favorable
geologic age. and character dip away from
a common centre-a dome-and all areas
where they dip away from central axis
an anticline or arch-where they dip away
from an area Of horizontal beds-a terrace,
are regarded as promising.
TX the dome, Rntlcline or terrace, located
IN rocks geologically favorable for oil, as
outlined above, is in entirely new region
where there is production, the geologist
can do little more than locate it and hope
Tor the best. The drill must ultimately de-
eide whether or not the favorable structure
contains oil in commercial quantities. How
ever, the geological can supplement the work
Of the drill by studying the materials which
come from the drill hole to see what type
u rock IT. is passing through If it cuts into
large body Of the rocks known to contain
no Oil the geologist knows that further
drilling in that hole is useless.
I'm areas such Az certain parts of the
Gulf and nid-continent fields, where the
rocks have been relatively little disturbed
and where the oil sands are fairly we'll de-
hhed and persistent, the geologist can tell
with considerable accuracy just where the
drill will find the oil sand. He cannot be
certain. but If the rock beds are we'll cx-
posed for study he can have n good idea as
70 whether the 'sand' will contain com
nsreisl quantities % oil
Where the underlying rocks are totally
obscnrsd by soil or by superficial deposits
'hs gsologist can do but little, because he
cannot sso the rock conditions.
To sum UP. the gsologist can eliminate