Montana oil and mining journal. [volume] (Great Falls, Mont.) 1931-1953, 1936-09-05
THE REVOLUTION AT kelvin

was then a signal TO the drilling con-
tractor to quit drilling. This is In spite
OF the fact that the largest wells i'm the
field are producing from strata BELOW
the top of the lime. The modern prac-
tice is to drill to the ssfirst break
soft, spOngy hOrizOn-in the lime The
day is at hand when every well win be
drilled THROUGH the lime before it is
ready for abandonment.
six inch hole is not q very large
space in area of a hundred thousand
acres, yet the oId-time operators were
lucky enough TO get this six-inch hole
into OiI-containing cracks and assures
in the lime, in about LEGO out Of 1900
wells drilled. They used to increase the
gathering space by shooting il with nitro
gIycerine. This worked In many i'm
stances. Again, it merely served TO seal
the walls by COMPRISING the formations
so that no oil could seep in.
In 1888 came the use Of acid. When
hydrOchloric acid is poured onto pure
lime, the lime disappears and I'm it's stead
is a chemical combination of the two
that is H20-water. One thousand gall
Ions of rs per cent acid is capable of dis
solving approximately 10 cubic feet OF
limestone.
Accordingly, when acid is forced into
one of these wells, It eats away a space
CRATE However, that Is the least im-
portant part of the action of acid It
Is not confined to the 8-fnch hole, to eat
evenly In a1I directions: it follows the
course of least resistance AS q result,
il there are any cracks I'm the lime, the
acid follows these cracks Acid is known
TO have travelled as far as 40 feet i'm
Kevin-Sunburst field. This was establish
ed by the fact that wen 44O feet away
from one that was acid treated, immed-
lately increased its production.
This acid may follow seam i'm the
limestone that is so small that only a
small seepage of oil can creep through.
The acid will enlarge that seam so that
i'm some instances large ''vugs" in the
lime have been tapped. This explains
why 12-year-oId 5-barrel wells have turn
ed into gushers: the acid has penetrated
a nearby cavity containing oil. Had acid
never been used, that cavity would per-
haps never have been tapped, since wells
are drilled on a scale OF one to five acres.
We recently saw a definition of acidi-
zatiOn. It follows:
1.-THE acidization of an oil or gas
well is a practice of placing within
the pcrmeable spaces i'm a producing
formation am acid that viii dissolve
the formation, thereby charging
drainage channels through which the
oil or gas may flow more freely into
the well, and opening new drainage
channels by dissolving barriers which
may be preventing the flow of oil or
gas into the well.
although the acid may enlarge
the diameter OF the bore hole at the
bottom Of a well, this enlargement
is secondary in Importance to the
enlarging or opening of drainage
channels within the formations which
lead into a well.
1.-THE basic idea behind the use OF
hydrochIoric acid for treating Iimy
formations is that IL not only dis
solves the lime but the resultant
products are gaseous and liquid
which provided the well has been
properly treated viii flow back out
of the formation into the well where
they can be brought to the surface
by flowing, pumping or swabbing.''
The operator who drills a well i'm
Kevin-Sunburst field today can get the
drainage from an area that would have
been provided by TEN wells I'm the OIden
days: even then it Is doubtful IL 10 wells
would have been as efficient as one well
with modern acidization.
The science of acidixatiOn is stiII I'm it's
infancy. This year they have brought