Arbuckle Oil and Gas Play
by Mitchell E. Henry and Timothy C. Hester
This play consists of approximately the upper 250 ft of the Cambrian to
Ordovician Arbuckle Group and extends over the entire province except in
the area where uppermost Arbuckle rocks are included in Deep Structural
Gas Play (i.e., except where the uppermost Arbuckle is below
13,000 feet in depth). Depths for the top of the Arbuckle Group in this
play range from about 1,000 ft to 13,000 ft (the upper limit of the Deep
Structural Gas Play). The "upper 250 feet" thickness limit for this play is a
conceptual boundary that divides the Arbuckle Group based on a perceived
level of exploration intensity rather than any type of geologic marker.
That is, the level of exploration of this upper part is much greater
throughout the province than is that of the lower part. Many wells that
report Arbuckle penetrations, however, were actually testing the deep
Simpson Group above, and only penetrate the upper part of the Arbuckle
by a few feet. Even though these particular wells probably do not
represent an adequate Arbuckle test (R.A. Northcutt, Oklahoma Geological
Survey, oral commun., 1993), the upper part of the Arbuckle still
remains significantly more well explored than the lower, main body of
the Arbuckle. Known accumulations are probably the result of the
combined effects of diagenetic reservoir enhancement and proximity to
major structural features. The higher level of exploration (relative to
lower Arbuckle Group strata) and a limestone and dolomite lithology are
the principal defining features of this play.
Reservoirs
Reservoir rocks for this play are Cambrian and Ordovician Arbuckle Group
limestones and dolomites; dolomite is expected to form the better
reservoirs. Solution enhanced porosity zones are important components
of this play. Reservoir quality is difficult to predict and is probably
quite variable (Gao and others, 1992). The Arbuckle Group in this play
is limited to about the upper 250 ft of the formation. Overall, the
Arbuckle Group ranges in thickness from about 300 ft in the northwestern
to more than 4,000 ft at the southern boundary of the play. The top of
the Arbuckle Group may be regionally unconformable.
Source rocks
Because most of the play is thought to have a strong stratigraphic
component and because only the upper 250 ft of strata is included in
this play, organic-rich rocks directly above or in the remainder of the
Arbuckle Group are considered the most likely hydrocarbon sources. In
areas where the Arbuckle Group is directly overlain by potential source
rocks, self-sourcing is not as important. Ordovician Simpson Group
shales directly overlie the Arbuckle Group in most of the province and
are considered possible hydrocarbon source rocks. Simpson Group rocks
are in the zone of oil generation (0.50 percent and 1.30 percent Ro)
throughout the play but are thought to be generally low in organic
content, with admixed types I and III organic matter (Burruss and Hatch,
1988). Regarding the internal source potential of the Arbuckle,
published reports contain conflicting conclusions (Trask and Patnode,
1942; Cardwell, 1977).
Timing
Potential Simpson and Arbuckle Group source rocks probably reached the
thermal zone of oil generation about 320 Ma (Schmoker, 1989). Porosity
enhancing unconformities at the top of and in the Arbuckle Group
developed prior to 320 Ma, significantly predating any petroleum
generation. Diagenetic porosity development by deep burial
dolomitization probably occurred after the Early Pennsylvanian (Gao and
others, 1992) but still within a time frame favorable for charging of
reservoirs.
Traps
Known major accumulations are found in combination traps and are near
major structural features. It is expected that most undiscovered
accumulations would also exist in combination traps. Arbuckle Group
production is generally restricted to the upper 250 ft of section and
located in the eastern and northeastern parts of the play along the
western flanks of the Nemaha Uplift, southern flank of the Pratt
Anticline, and southwestern flank of the Central Kansas Uplift. Seals
for this play may result from low-porosity zones of Arbuckle carbonates
in the Group or from overlying low-porosity rocks.
Exploration status and resource potential
The earliest major discovery assigned to this play was at the Garber
field in 1925. The largest accumulation is in the Bradbridge field with
an estimated ultimate recovery of 27 BCFG. More than 1,800 wells
contain reports of Arbuckle-Ellenberger Group rocks and about 110 of
these are producing wells. Four major reservoirs were assigned to the
play, two of these are gas and two are oil accumulations. Reported API
gravity for the two oil accumulations is 38°. Depth of known major
reservoirs ranges from about 4,200 to 6,300 ft.
This play is not well explored. Drilling intensity and hydrocarbon
production generally increases toward the major structural features in
the northern and eastern parts of the play. Because of the apparent
relationship between reservoir quality and the presence of major
structural features, the less explored portions of the play are also
considered less prospective for production. However, because the
Arbuckle Group is not well explored, there is considerable uncertainty
as to the potential for this play to contain significantly large
petroleum accumulations. This uncertainty is shared with other plays
that include Arbuckle Group rocks. Overall, the future potential of
this play is not considered high.
Play Map
References
Burruss, R.C., and Hatch, J.R., 1989, Geochemistry of oils and
hydrocarbon source rocks, greater Anadarko basin--evidence for multiple
sources of oils and long-distance oil migration, in Johnson,
K.S., ed., Anadarko Basin Symposium, 1988: Oklahoma Geological Survey
Circular 90, p. 53-64.
Cardwell, A.L., 1977, Petroleum source-rock potential of Arbuckle and
Ellenburger Groups, southern mid-continent, United States: Colorado
School of Mines Quarterly, v. 72, no. 3, 133 p.
Gao, Guoqiu, Land, L.S., and Folk, R.L., 1992, Meteoric modification of
early dolomite and late dolomitization by basinal fluids, upper Arbuckle
Group, Slick Hills, southwestern Oklahoma: American Association of
Petroleum Geologists Bulletin, v. 76, no. 11, p. 1649-1664.
Schmoker, J.W., 1989, Thermal maturity of the Anadarko basin, in
Johnson, K.S., ed., Anadarko Basin Symposium, 1988: Oklahoma Geological
Survey Circular 90, p. 25-31.
Trask, P.D., and Patnode, H.W., 1942, Source beds of petroleum: American
Association of Petroleum Geologists, 566 p.
Kansas Geological Survey, Digital Petroleum Atlas
Comments to webadmin@kgs.ku.edu
Updated May 28, 1998
URL=http://www.kgs.ku.edu/DPA/frontEnd/Anadarko/Arbuckle/provSum.html
