SHOOT COULD AID DEEP EXPLORATION ALONG OHIO

Paul Edwin Potter
University of Cincinnati
Cincinnati

A seismic line could provide a continuous, coherent tie between the Illinois and Appalachian basins.

Riverine seismic of the Ohio River and its tributaries provides the cheapest cost per mile data acquisition to study the poorly understood deep structures of salient parts of the two basins and the Cincinnati arch from the Mississippi River eastward to the Allegheny front in Pennsylvania.

The Ohio River watershed spans parts of the Appalachian and Illinois basins and includes all of the Cincinnati arch and Nashville dome. This region has produced commercial quantities of oil and gas for more than a century and remains an important petroleum region for the U.S.

It is also a vital part of the heartland of America. The watershed includes parts of 14 states, covers 204,000 sq m (652,800 sq km), or nearly 7% of the conterminous U.S., and has a population of more than 26 million. Within the watershed is vast, diversified industry and a rich agricultural region plus substantial coal and chemical industries. Other authors provide more details of economic importance of the Ohio River basin to the U.S.1 2

RIVERINE SEISMIC LINE

A seismic line along the Ohio river would dramatically alter the geologic perspective of this vital region and rank high on any list of regional geologic studies of the watershed.

Such an internally coherent line would provide a "common denominator" to correlate existing short seismic lines that terminate at or near the river, permit correlation of deep seismic facies across the Cincinnati arch between the Illinois and Appalachian basins, supplement existing Cocorp lines in the Midwest, and open the way for later studies along the Mississippi River.

An important derivative would be improved skills for "shallow water" riverine seismic studies elsewhere.

SEISMIC TARGETS

Extending from Cairo, Ill., to beyond Pittsburgh, Pa., a riverine seismic line would provide a continuous seismic profile of 981 miles for the Ohio river and open the possibility of later profiles of 441 miles for its five major navigable tributaries.

Along the traverse, basement lies 3,000-40,000 ft or more below river level. Important structures and geologic sites crossed by the Ohio and its tributaries, or are near it, include:

1. the head of the Reelfoot rift in southern Illinois;

2. the Rough Creek graben of western Kentucky and its extension into southern Illinois, the Eagle Valley syncline;

3. the proposed site of the Illinois basin ultradeep drillhole in southern Illinois;

4. the south end of the southern Indiana arm or Wabash Valley rift;3

5. the west side of the Cincinnati arch from Louisville to its crest at Cincinnati, where a new Precambrian rift has been delineated;4 5

6. the east side of the arch, which has an abrupt increase in eastward dip at about Maysville, Ky.;

7. the Waverly arch that crosses the Ohio river between eastern Kentucky and southern Ohio;

8. parts of the deep Rome trough along much of the West Virginia-Ohio line.6

9. the famous Burning Springs anticline6 of West Virginia; and

10. the southern extension of the Cambridge arch in southeastern Ohio.7 8

The four navigable tributaries also provide shorter transects each with significant geologic interest:

1. the Green River (188 miles) crosses the Rough Creek graben of Kentucky;

2. the Kanawha River (92 miles) in West Virginia crosses much of the Rome trough at right angles;

3. both the Monongahela (167 miles) and Allegheny rivers (79 miles) provide extended access to the deeper part of the Appalachian basin near Pittsburgh.

OIL, GAS, MINERAL POTENTIAL

Interest is high in these deep structures because they offer promise of extending the region's oil, gas, and mineral potential. For example, the first deep Precambrian oil play occurred recently in equivalent rocks of the Midcontinent rift in Minnesota. The eastern Midwest has also benefited from the deep seismic studies of Cocorp,9 10 which show a deep layering below known Cambrian rocks.

An Ohio River traverse would also contribute significantly to understanding of thrusting in basement rocks and how it might relate to either Alleghenian or even Grenvillian events.11

Oil and gas exploration in the overlying Paleozoic section will also benefit in several ways. The proposed transect passes near and between many oil fields of the Appalachian and Illinois basins, and the proposed seismic line will help clarify relationships between deep structures and more well known shallow ones such as the Cambridge arch and the Burning Springs anticline.

And in broad perspective, such a line would provide new vistas on the fundamental relationships between the Illinois and Appalachian basins and the intervening Cincinnati arch.

Finally, successful completion of this project would open the other parts of the nation's inland waterways to riverine seismic exploration. A model for riverine seismic in North America is provided by Petroleo Brazileiro SA in Brazil, where riverine seismic on the Amazon and Solimes rivers and their tributaries is the only feasible way to explore seismically the giant Amazonas and Solimes basins.

An experimental line has also been run in the Hudson river,12 and some lines have been run in Florida canals.

ACQUIRING DATA

Acquisition crews probably would use a 2,727 m (60 fold) streamer with an air gun source and a pop every 25 m. This energy source is environmentally friendly and should minimize environmental permitting.

The project would take 3 years, starting in fall 1991. It is anticipated the line would be run in fall 1992, when pleasure boat traffic is minimal and the river is normally not in flood.

The proposed budget of $2,703,076 includes funds for field data, acquisition and processing of a line from Cairo to Pittsburgh, short term support for one member of each geologic survey, publication costs by appropriate state geological surveys, travel money for a supervising executive committee, and salary for the committee chairman/principal investigator.

The nonseismic budget includes publication costs, travel funds, and limited compensation for one representative from each of the five state surveys and the U.S. Geological Survey.

Each survey is to supply matching time for its personnel. No equipment or graduate student support is requested.

A small executive committee of selected industry, state, survey, and some university personnel representing each of the five states of Kentucky, Indiana, Ohio, Pennsylvania, and West Virginia, and the USGS would administer the project.

Such a committee would work with a contractor experienced in marine seismic studies to plan the project and coordinate resulting publications. It would routinely meet at Cincinnati at the center of the Ohio River basin.

DISSEMINATING RESULTS

Five atlases should be published by the five surveys: one for the Kentucky and Illinois portion of the Ohio River, another for Indiana-Kentucky portion of the river, one for Kentucky and Ohio, another for Ohio-West Virginia, and one for Pennsylvania.

Each atlas will contain paired annotated and unannotated seismic lines plus a strip map of geology proximal to the river, one that includes deep wells and locations of seismic lines available from brokers.

A geologic cross section emphasizing the deeper units would be included. The format should resemble that of the American Association of Petroleum Geologists' successful seismic atlases but will be much smaller, less expensive, and unlike their role model be directly relatable to exploration and research.

The scale of the seismic sections should be one half inch to 1 mile, with a larger scale for limited reaches of the river of special interest. The USGS, in cooperation with the five state surveys and university personnel, would publish a final regional study spanning the entire Ohio River.

The processed displays will be given to the respective state surveys and the USGS and made public after a waiting period of 120 days from completion of processing.

During this time the contracting company will have the right to sell lines to interested groups to help defray costs. It is notable that even at the maximum cost of $2,702,076, this low cost of $2,754/mile includes data acquisition, processing, and publication.

Regional offset lines could be run along navigable tributaries in conjunction with the project for very reasonable cost. For instance, it is estimated that a 92 mile downdip seismic line could be shot along the Kanawha River in West Virginia into the deep Appalachian basin for only $248,548.

REFERENCES

1. Hahn, R.A., Ed., Ohio River navigation system 1988 report: U.S. Corps of Engineers, Ohio River Div., Cincinnati, Ohio, 79 p.

2. The Economist, The Ohio River, a tale of three cities: The Economist, Mar. 31, 1990, pp. 28-29.

3. Sexton, John L., Braile, L.W., Hinze, W.J., and Campbell, M.J., Seismic reflection profiling studies of the buried Precambrian rift beneath the Wabash Valley fault zone: Geophysics, Vol. 51, 1985, pp. 640-660.

4. Shrake, D.L., and six others, Expect the unexpected-major Precambrian rift-like basin underlies Cincinnati Arch: Geology, 1990, in review.

5. Potter, Paul Edwin, New rift under Cincinnati arch helps explain preglacial drainage: Compass, Vol. 67, 1989, pp. 11-13.

6. Schumaker, Robert, Effects of basement on sedimentation and detached structure, Appalachian basin in McDowell, R.C., and Glover, Lynn III, Eds., The Lowry volume: Studies in Appalachian Geology, Department of Geological Sciences. Virginia Polytechnic Institute, Blacksburg, Memoir 3, 1986.

7. Lockett, John, Development of basin structures in north eastern U.S.: AAPG Bull., Vol. 31, 1947, pp. 429 446.

8. Rogers, John, Mechanics of Appalachian foreland folding in Pennsylvania and West Virginia: AAPG Bull., Vol. 47.

9. Hansen, M.C., "How the world was made"-the Cocorp traverse across Ohio: Ohio Geology Newsletter, Winter 1989.

10. Pratt, T., and seven others, Major Proterozoic basement features of the eastern Midcontinent of North America revealed by Cocorp profiling: Geology, Vol. 17, 1989, pp. 505-509.

11. Beardsley, R.W. and Cable, M.S., Overview of the evolution of the Appalachians: Northeastern Geology, Vol. 5, 1983, pp. 137-145.

12. Bond, G.C., Diebold, J., Menke, Bill, and Buhl, P., The last cruise of the R.V. Conrad, a multichannel seismic experiment in the Hudson River: Lamont-Doherty Geological Observatory of Columbia University (Palisades, N.Y.), 1989, pp. 33-38.

BIBLIOGRAPHY

Black, Douglas F.B., Basement faulting in Kentucky: Proceedings of the 6th International Conference on Basement Tectonics, Sept. 1620, 1985, Santa Fe, N.M. (Int. Basement Tectonics Assoc., Salt Lake City, Utah), 1986, pp. 125 139.

Leighton, M.W., and Eidel, J.J.. Preproposal Illinois basin ultradeep hole: Illinois Geological Survey, Urbana, Ill., 1987, 78 p.

Shirley, K., Ohio buried basin challenges theory: AAPG Explorer, March 1990, pp. 8-11.

Copyright 1990 Oil & Gas Journal. All Rights Reserved.