Charles C. Perry Jr.
Perexco Corp.
Tulsa
A new frontier area for Cambro-Ordovician Arbuckle oil and gas exploration now beginning to attract serious attention lies between the frontal fault system located along the southwestern edge of the Anadarko basin and the Wichita-Amarillo uplift.
Recent discovery of Arbuckle oil and gas at the 1-1 Susie Pi-Hoodle in 1-6n-13w, Caddo County, Oklahoma, forces many explorationists to take a new look at the area's prospectivity.
The Oklahoma Geological Survey and the USGS jointly studied the Anadarko basin since 1984 and have published Circular 90 which is the proceedings of a symposium held in April 1988. In this issue, 35 separate papers, abstracts, and short reports are presented. Beginning with Cement field in 1917, more than 50 significant fields have been discovered in the basin, with a cumulative production of more than 5 billion bbl of oil and 82 tcf of gas. The new area of exploration is contiguous with and forms the southwestern shelf and mountain front of the Anadarko basin.
In Circular 90, a paper titled Constraints on the Anadarko Basin-Wichita Uplift Boundary Interpreted from Aeromagnetic Data, by M. Jones-Cecil and A.J. Crone; on p. 232 regarding the possibility of sedimentary rock existing near the Meers fault and the Slick Hills, quote "thus, the material overlying the highly magnetic body in the vicinity of the Slick Hills could be either sedimentary rock, rhyolite, or--most likely--some of each."
This conclusion is critical information for the interpretation of new seismic data now being acquired in this same region. It is quite possible that sedimentary and igneous rock exist in close proximity and may be superimposed on each other by complex thrust faulting in an area that extends for a distance of 10 or more miles north of the Meers fault.
A second paper in Circular 90, p. 78, Structural Imprint on The Slick Hills, Southern Oklahoma, by Donovan et al. demonstrates that the deformations and rotations of the sediments were created by left-lateral transgressive (oblique compressional) forces with resulting slip faulting and left lateral frictional drage. In Fig. 1, the trace of the new Perexco seismic Line 1 has been drawn across the northwestern end of this geological map. Fig.2, a schematic cross section, shows many of the major features crossed by a new seismic line, however as would be expected, it presents an oversimplified description of the area. The Meers Valley, adjacent to the Meers fault, contains "megabreccias" with house-size boulders of carbonate interbedded with pebble conglomerates of similar composition and clasts derived from the Kindblade formation of the Arbuckle, clearly demonstrating that Arbuckle sediments were deposited in the area.
For several years, Arbuckle gas has been produced by six wells in Mayfield field, 10n-26w, Beckham County, Okla,. Discovered in 1971 by Helmerich & Payne 1 Cupp, the field also includes 17 Hunton wells. In 1967, Arbuckle production was found far to the northwest in Wheeler County, Texas, in Laketon pool. This pool was opened in the Ellenburger Cambro-Ordovician in 1954 and for many years was the only pre-Pennsylvanian pool in the basin. Today, this discovery takes on new and broader proportions and meaning. Several wells were drilled on faulted domal structures with production from fractured Arbuckle which had undergone leaching, resulting in high porosity development at the unconformity level.
Interpolating between these various producing areas indicates that Arbuckle production may be located along a fairway 10 to 30 miles wide which may extend for more than 250 miles across southwestern Oklahoma from Ardmore northwestward as far as Wheeler County, Texas.
Looking for Arbuckle production in this new area is made practical now that modern vintage high channel, high fold seismic data can be processed to resolve the structural complexities of these mountain front thrust zones. Such a seismic program is now in progress, operated by Perexco Corp. of Tulsa, and jointly underwritten by Helmerich & Payne, Inc., and Santa Fe Energy Resources. A new regional seismic line has just been completed across 22 miles of this frontier, tying to the Susie Pi-Hoodle Arbuckle discovery in 1-6n-13e in Northeast Alden field, and extending to the southwest for an additional 15 miles to terminate on top of igneous rock (Carlton rhyolite), one of the first such lines to do so.
The southwestern portion of this regional line crosses severely folded and overthrusted rocks of the original shelf or platform. This mountain front complex is certainly within a structural framework for hydrocarbon exploration more difficult to resolve than that found along the leading edge of the boundary fault zone of the Anadarko basin where most drilled has occurred to date. This area, however, has about the same complexity as the terranes of the Anschutz Ranch East field in the Rocky Mountain Overthrust Belt or the structures penetrated by the Zipperer discovery of Amoco (Spiro-Wapanuca production) located south of the leading edge of the Choctaw fault in the Arkoma basin.
The results of recent improvements made in seismic instrumentation, data acquisition and processing are shown by examples , shown in Fig. 3 as a "brute stack" and in Fig. 4 as a final stack, or structural section. Both DMO final stack in Fig. 5 and DMO migrated time sections in Fig. 6 using "dip move-out" software routines (by Seismograph Service Corp.) have succeeded in better imaging the seismic reflectors in their true relative positions. The final interpretive steps, including both forward and inverse geological-geophysical modeling procedures, have yet to be performed on these data. The improvement in data quality demonstrated between Figs. 3 to 6 derives from greater intensity of data acquisition effort, new techniques, better processing software, and state-of-the-science instrumentation. The additional detail and greater structural resolution of these new data now provide the base upon which a more accurate and plausible geological interpretation can be made for hydrocarbon exploration.
Additional regional seismic lines are being completed this year to continue the delineation of several major features of exploration interest in the Mountain View-Meers area of Oklahoma. This activity coincides with and will be followed by minerals leasing in an area where about 80% of the acreage is still open. A number of companies are poised to take these normal exploration risks in order to share in the rewards that may result form timely investments within a new frontier.
With natural gas now recognized as the cleanest, environmentally preferred energy source of the immediate future, this frontier area certainly fits into a special category likely to provide new reserves eagerly sought by the petroleum industry.
Wildcat drilling, as always the final proof of success in any frontier area, should follow soon and expand behind the geological-geophysical studies now commencing in earnest along this extensive trend.
Copyright 1990 Oil & Gas Journal. All Rights Reserved.