Montana oil and mining journal., 1942-06-06

The textbooks tell us how oil and gas
accumuIates:
The earth's surface is nexed or bent up
ward by mountain building forces forming
a trap shaped like an inverted bowl.
Oil, floating on top of water, migrates
through porous sandstone, seeking escape
travelling ever upward until it is stopped by
some barrier: either fault which brings
imperviOus beds against the sandstone else
a bOwl-like trap which haIts the migration,
as water surrounds it on all sides Then gas,
being lighter than the oil, forms at the top
of the dome.
Thus, If the textbook theory worked out,
Kelvin should have gas at the top, then down
the flanks should be the oil and below the
oil should be water.
However, some of the biggest water wells
in Kevin area are at the top Of this DOME
The oil is sometimes found at or near the
top; sometimes part way down the fIanks
where 1t belongs, and then again it is found
on the lowest closing contours, where the
water should be.
1t has been determined that Kelvin field
does not abide by the rules Of accumulation
of oil. A well near the top Of the dome may
get no gas and no oil but find water Again,
well on the lower contours may get oil and
no water and not infrequentIy such wells get
gas. The newly developed gas supply Of
Kelvin, IL miles west of town, is on one OF
the lowest closing contours of the Kelvin
DOME
Drilling into the lime the drilier always
finds water at one or another horizon, Il
he keeps on drilling. Thus far, a water hori-
zOn has meant "finis" to Kelvin drilling. In
Turner Valley field, where oil likewise comes
from the Madison lime, the driIIers case off
the water and continue on down, but not
in Montana 1t has been determined, how
ever, that there is always adequate water to
insure that any oil trapped in Kelvin area
will be kept there by the hydrOstatic head
Multi-thousand barrel wells have been
completed in Kelvin field in years past al
ways on an accidental" location. None ever
set out to bring i'm a thousand barrel well
and did So w. M. Fulton was drilling with
the av0wed intention Of getting himself a
flock OF 1O-barreI wells" when he decided 10
settle down" on the Byrne lease The third
well he drilled made not only 10 but many
thousand barrels per day. Within Is months
1t had made a million dollars worth Of oil
Operators who have rushed in TO offset
flowing wells found that it is as easy to get
a dry hole 44O feet from a gusher as In
any other location In the field. Frequently
a big well has been surrounded by small
producers or dry holes. 1t slowly deyeIoped
In the minds Of operators that the big wells
resulted from the drill tapping a crack in
the Madison lime-a vug filled with oil. The
next well drilled, few rods back, had only
a little seepage from that crack or vug A
well stiIl farther back, received no benefit
from that vug because the lime formation
Is not like sand: oil does not travel through
Il IateraIIy.
'Tf oil does not travel through this lime
literally, then how does it accumuIate?"
someone asked. After long study someone
vertically We know not one per-
'On in the industry today who does not be-
ieve that the oil In Kelvin comes up through
racks or fissures In the lime accommodating
n small pools when halted in UPWARD
by the imperviOus black shaIes
If the Ellis Occasionally some oil seeps on
upward through the Ellis and collects In the
Sunburst sand. The Sunburst sand, a fresh
water horizon, is not considered q source
Ock. 1t is a mere host rock for escaping
III. Neither is the top of the Madison lime a
Ource rock.