AUDAX EXPLORATION, INC
P.O.
BOX 1825
903-882-8813
BUSINESS/FAX
EAST
FORK PROSPECT
Kaufman County, TX
One
of the three remaining major exploration plays to be made is the Lower
Paleozoics structures under younger Permo-Penn thrusting. The formations associated
with these structures in large measure are restricted to the Simpson and
Arbuckle Groups. Both are excellent reservoirs and producers in Oklahoma,
Texas, Michigan and Ohio. Of late the Middle Ordovician has been extended into
New York, West Virginia, Tennessee and Kentucky.
The
Simpson has been under-explored in Texas, particularly in Central Texas. Even
the lower portions of the Arbuckle below the West Spring Creek and Kindblade
Formations, for all practical purposes, is virgin to exploration even in
Oklahoma.
Reduced
to the simplest terms, the various formations within the Arbuckle Group exhibit
reservoir properties when their geologic history is comprised of certain
discrete tectonic events. When these events are combined, reservoir rocks
result. The Arbuckle produces from essentially two types; one is the eroded
remnant typified by Osage County, OK. The second, and most prolific, comes from
the type reservoir known as hydrothermal dolomite (HTD), or tectonic dolomite
in the common vernacular.
HTD
results from a series of tectonic and hydrocarbon source processes. The first
is that the original fabric of the rock was fine-grained limestone; it in turn
was fractured predominantly by the
Permo-Penn orogeny. The limestone was then subjected to hot thermal,
magnesium-rich brines invading the fractured formation from below during the
Permian heat flow. This in turn converted the limestone into dolomite, causing
a volume reduction, or porosity increase. Once the hot brines had done their
work, the hydrocarbons followed, essentially trapping into both anticlinal and
linear configurations.
The
porous sections often reach extraordinary thicknesses; KY (570Õ), Arkansas
(620Õ), OK (400Õ at Healdon, most of a 2500Õ section at Wilburton, over 300Õ at
Cottonwood Creek), Michigan (170Õ Albion-Scipio), TX (400Õ), and TN (320Õ). NY
and others exhibit similar numbers. These thicknesses are from microlog and
density-neutron logs. Bit drops of 25Õ-50Õ are not uncommon.
Reserves
range from 500 BCF to 50 MMBO; reservoir sizes are usually in the 1000s of
acres from the anticlinal traps to 18 miles x ¾ miles for the linear.
Notable fields in OK are SE Hoover, Healdon, Cottonwood Creek, Wilburton; in
TX, KMA, Bramlett; NY, Steuben County, MuckÕs Farms, et al; in TN, Swan Creek;
KY, numerous fields in Knox and
Adair Counties.
The
East Fork Prospect falls into the modified anticlinal category. It is underlain
by an extremely strong and large Bouguer anomaly. Regionally, East Fork lies on
the Lower Paleozoic shelf edge trending from the McCurtain County, OK to south
of San Antonio. It is turn is overlain by the Lower Penn, thin-skinned, buried
Ouachita mountain chain. There are very few exploration tests within this
60-mile wide belt; of those, there is a mixed bag of lithology associated with
the Arbuckle Formation. As summary of those tests are as follows:
Sohio #1 Weyerhouser, McCurtain County, OK; in excess
of 300Õ of reservoir
quality Arbuckle section. Tested gas with heavies, excellent pressures.
Large anticline with no root;
looks to be thrust from original shelfal
position NWÕward. High heat flow exhibited in section, but porosity
very well preserved.
Hunt #1 Nealy ,
Lamar County, TX. Large anticlinal structure originally deposited
within the low-energy
SE OK trough. High heat flow exhibited,
rocks
very tight, non-reservoir.
IMC #1 Wassom, Hunt County, TX; monoclinal pop-up
structure resulting from
thrusting, no heat flow at all, completely non-metamorphosed, reservoir
quality rocks within Arbuckle section, with gas shows and water. Seal
integrity well-preserved, bottom-hole pressures .51 gradient. TD in
Kindblade Formation of Arbuckle Group. Shelfal
deposition.
Amoco #1 Price, Ellis County, TX; no data available.
Presumed to have
penetrated into sub-thrust Arbuckle.
Shell #1 Barrett, Hill County, TX; anticlinal structure, large rollover
known
as the Waco Uplift. TD in pre-Cambrian quartz diorite. Total section
Arbuckle was 6000Õ, making the original
deposition off-shelf. Well is
along strike with well penetrating the entire section, with only 3000Õ.
Structure has no roots, has been thrust
over 50 miles NWÕward. Very
heat flow, marbleized, no reservoir quality at all.
The
East Fork Prospect occurs along a series of high-amplitude Bouguer anomalies,
which in my mind, represent the Lower Paleozoic shelf as it is today. Not
one exploration test of the
above has been drilled on any one of those anomalies that I consider at or near
the original shelfal position. It is the shelfal areas that fostered the higher
energy, fine-grained rocks necessary for optimum fracturing in the first place.
Moreover, the shelfal position as opposed to off-shelf, is what allowed
aerial-sub-aerial leaching and erosion. The latter elements are what indicate paleo-highs.
This tectonically undisturbed shelfal area is where I consider the area which
has been preserved, and less likely to have undergone high heat flow.
As
we write, there is a well drilling an 18,500Õ well to test a large structure in
the northern part of the trend which has over 60,000 acres (yes, 60,000
acres!!) and over a second of structural reversal. It, like East Fork, is
interpreted to have been moved very little from its original position on the
shelf, and is expected to have reservoir rocks.
The
East Fork Prospect indicates closure approaching 40,000 acres, perhaps as much
as 50,000 acres. The reservoir size indicated by Reeves Exploration is at least
12,000 acres, and may be as much as 15,000-16,000 acres. The relation of trap
to structure is in the 40%-50% range, which is within accepted boundaries of
fill-up.
If
the 12,000 acres is productive from the Arbuckle Group, and there is an average
of 200Õ of reservoir, then reserves as follows can be accommodated:
12,000
A x 200Õ x .5 MMCFGPAF = 1.2 TCF
12,000
A x 100Õ x 200 BOPAF = 240 MMBO
It
is somewhat uncertain as to the depth of the objective Middle Arbuckle Group in
the test well. To that end, I recommend either buying or shooting a long
West-East seismic line across the proposed drillsite and establish proper
depth/time relationships. In the alternative, one can run magnetotellurics.
As
regards to drilling procedures, it had been my experience with HTD reservoirs
that drilling conventionally with mud is counterproductive, and will, in most
cases, destroy the reservoir. I can prove this with numerous examples in wells
with which I am intimately familiar. I have also proved the following method of
drilling in HTD reservoirs in TN.
1.
Set pipe to the base of
the Mesozoic at approximately 2000Õ
2.
Drill with the most
effective mode of drilling to the base of the thrust Ouachitas and set pipe.
Air is recommended.
3.
Drill the sub-Ouachita
section with either air or mist, with steel tanks, essentially completed to the
tanks or pipeline.
Respectfully
submitted,
L.F.
Berry, CPG
LFB/lfb