OHIO ROSE RUN, BEEKMANTOWN EXPLORATION HEATS APPALACHIANS

Ronald A. Riley
Ohio Geological Survey
Columbus

Oil and gas exploration along the western margin of the Appalachian basin is experiencing renewed optimism as a result of recent significant discoveries in the Rose Run sandstone and Beekmantown dolomite of the Knox dolomite. In spite of the maturity of this basin and the density of shallow wells, numerous oil and gas pools and fields are thought to exist and continue to be found in these deeper Knox horizons.

Oil and gas pools and fields in the Rose Run and Beekmantown currently exist from south-central Ohio to central and eastern Ohio, and extend into extreme Northeast Ohio (Fig. 1) (12524 bytes). In recent years, exploration for these Knox hydrocarbons has been taking place at an accelerated rate across the eastern half of the state. Paleotopographic highs (erosional remnants) beneath the Knox unconformity are the dominant trapping mechanisms for Knox hydrocarbons in Ohio.

PRODUCTION HISTORY

Natural gas was first produced from the Rose Run sandstone in 1965 from the Kin-Ark 1 Erb (Permit No. 1328) in Holmes County, Ohio. This discovery well was drilled to a depth of 6,570 ft and had an initial production rate of 2.1 MMcfd of gas and 10 b/d of oil. Subsequent Rose Run drilling occurred primarily in the late 1980s to the present and led to the extensive development of Baltic field in eastern Coshocton and Holmes counties (Fig. 1) (12524 bytes). Average depth to pay in this field is approximately 6,500 ft.

As a result of Rose Run exploration in eastern Coshocton County, oil and gas discoveries were made in the overlying Beekmantown dolomite in Bakersville field. The discovery well drilled in 1980 was the Stone Resources 1 Mizer (Permit No. 3893) and had an initial production rate of 1 MMcfd of gas and 2 b /d of oil. Additional drilling in the vicinity of the 1 Mizer well led to the development of Bakersville field in eastern Coshocton and western Tuscarawas counties (Fig. 1) (12543 bytes). Average depth to pay is approximately 6,900 ft.

The Rose Run discovery had a profound impact on the mindset and exploration strategy of Ohio operators, who for many decades had concentrated drilling only shallow objectives such as the "Clinton" sandstone. Now their efforts also were focused on the Rose Run and other deep Knox targets such as the Beekmantown dolomite and Copper Ridge dolomite. This exploration strategy continues unabated today and will probably extend through the turn of the century.

Today, Ohio oil and gas operators are drilling record numbers of deep Knox tests. From 1983-93, Knox drilling increased dramatically (Fig. 2) (10321 bytes) and is accelerating. Rose Run and Beekmantown drilling more than doubled to approximately 260 wells in 1993 from about 120 in 1992. Approximately 300 Rose Run and Beekmantown wells are expected to be drilled in 1994. Better understanding of the geology and increased use of reflection seismic data have led to an increase in the success rate of locating commercial quantities of oil and gas in these deep Knox units. The success rate from 1989 to 1993 showed a steady increase from 24-61% for productive Rose Run and Beekmantown wells (Fig. 2) (10321 bytes).

TRAPPING MECHANISMS

The Knox in Ohio consists of the rocks overlying the Eau Claire, Kerbel, or Conasauga formations and underlying the Knox unconformity. In eastern Ohio where the Rose Run sub-crops, the Knox has been subdivided into the following units in ascending stratigraphic order: Copper Ridge dolomite, Rose Run sandstone, and Beekmantown dolomite (Fig. 3) (11554 bytes). The Rose Run sandstone was first named by L.B. Freeman in 1949 from the Judy and Young 1 Rose Run Iron Co. well in Bath County, Ky. Although there was no commercial oil or gas production, a show of gas was reported in the Rose Run, along with much water. By the mid-1960s, several deep tests in eastern Ohio had penetrated equivalent rocks. The name Rose Run was applied by drillers and petroleum geologists to subdivide the Knox dolomite.

The Rose Run sandstone is the only laterally persistent sandstone unit within the Knox. The sandstone unit can be correlated in the subsurface from eastern Ohio, where it subcrops beneath the Knox unconformity, to northeast Kentucky, into western West Virginia, Pennsylvania (upper sandy member of the Gatesburg formation equivalent), and extends into New York as part of the Theresa formation. In Ohio, average thickness for the entire Rose Run interval is approximately 110 ft and consists of a sequence of up to five porous sandstone lenses interbedded with nonpermeable dolomite. Petrographically, these sandstone lenses are white to gray, fine- to medium-grained quartz arenites to subarkoses, that are locally glauconitic. These sandstone lenses commonly can be correlated reliably for a distance of 20 miles or greater. Porosities range from 4-15% and average 9%.

The Beekmantown consists of a gray to brown, fine-to medium-crystalline, mottled, nonpermeable dolomite that locally contains algal stromatolites. The reservoir for the Beekmantown dolomite occurs in zones of well-developed vuggy porosity near the Knox unconformity, and in fracture zones along fault trends. These vuggy zones have porosities that vary from 5-20% and average 15%.

In terms of migration, hydrocarbon entrapment, and reservoir performance (porosity and permeability), the paleotopography, its exposure, and resulting karst processes on the Knox unconformity are the single most important geologic factors influencing gas production in the Knox. Primary trapping mechanisms for the Rose Run and Beekmantown include paleotopographic highs (erosional remnants), vuggy porosity zones, faults and associated fractures, stratigraphic updip truncation against the Knox unconformity, and basement-related structures (Fig. 4) (15271 bytes). Channel sandstone traps, structural closures, and small anticlinal noses are less common.

Seismic reflection data are extremely useful in locating erosional remnants. These are subtle features averaging 40 ft in relief, although some exceed 90 ft, and typically are 80 acres or less in areal extent. Knox erosional remnants may be capped with Beekmantown dolomite and often contain a thin section of Wells Creek formation. The Wells Creek formation may be absent in some of the larger remnants. In some instances detailed subsurface mapping and seismic reflection data show these paleotopographic highs to be positioned beneath structurally high features in the Ordovician Trenton limestone and occasionally as high as the Silurian "Packer Shell." It is not known whether this effect is caused by draping of sediments, structural reactivation, or both. Seismic reflection data also reveal that many of these paleotopographic highs are related to reactivated basement structures.

PRODUCTION CHARACTERISTICS

Average decline curves (Fig. 5) (18061 bytes) indicate production for an average Rose Run well begins at approximately 72 MMcf of gas for the first year. Decline of the average well is fairly rapid during the first year and is followed by a gradual decline over the life of the well. Some Rose Run wells are plugged back to the Silurian "Clinton" sandstone within 5 years; however, the average well production life should extend past 15 years. Average cumulative gas production after 10 years in the Rose Run is approximately 400 MMcf. The more exceptional wells, such as the Kin-Ark 1 Erb, have produced steadily for 25 years with a cumulative gas production of 1.99 bcf of gas and 3,400 bbl of oil. Cumulative production for Baltic field from 1965 through 1992 is approximately 20 bcf of gas and 450,000 bbl of oil from approximately 130 wells, with the majority of these wells having been drilled since 1987.

The Beekmantown dolomite of Bakersville field exhibits the highest producing rates of any reported Knox producing unit in Ohio on a well by well basis. Average production for the first year is similar to the Rose Run at approximately 69 MMcf of gas .4 The Beekmantown decline rate is much lower, however, and declines less rapidly than the Rose Run reservoir (Fig. 5) (18061 bytes). The higher sustained rates may be the result of the higher porosities and permeabilities and a larger drainage area per well. Average cumulative gas production after 10 years is approximately 680 MMcf. The immaturity of Bakersville field precludes the determination of the production life expectancy; however, the 1 Mizer well has produced steadily for over 13 years. The average decline rate indicates production may extend up to 30 years. This is one of the best Knox gas wells in the Appalachian basin with over 2.7 bcf of gas produced during the first 13 years. Cumulative gas production for Bakersville field from 1980 through 1993 is approximately 9 bcf from 33 wells.

RECENT HIGHLIGHTS

Historically, Rose Run and Beekmantown drilling and production have been concentrated along the subcrop in north-central Ohio in Coshocton and Holmes counties. In the past several years, however, exploration and production have been extending further north and south along the subcrop (Fig. 1) (12524 bytes). In 1990, the exploration emphasis on Rose Run activity shifted to Muskingum County with the discovery of Rose Run production by the Oxford Oil Co. J-1 Miller Goodrich Unit (Permit No. 7629) in Muskingum Township. This well was drilled to a total depth of 5,834 ft and had an initial production rate of 500 Mcfd of gas and 10 b/d of oil. Cumulative production through 1993 was 282 MMcf of gas and 3,228 bbl of oil. Significant discoveries followed in this county such as the Clinton Oil Co. 3-1554 McBride Unit (Permit No. 7679) in Cass Township. This well had an initial production rate of 1 MMcfd of gas and 2 b/d of oil. Cumulative production from 1991 through 1993 was 450 MMcf of gas and 9,350 bbl of oil. Also in Cass Township is the Oxford J-1 Moore (Permit No. 7718) drilled in 1992. Initial production rates were 500 Mcfd of gas and 50 b/d of oil. Cumulative production through 1993 was 288 MMcf of gas and 26,460 bbl of oil. Drilling and permitting of Knox wells remains very active in this county.

In 1993, E.C. Redman/Redman Oil made a new field discovery in the Rose Run with the 1A Stevenson lease (Permit No. 34) in Wayne Township of Pickaway County. Total depth for this well was 2,480 ft with an initial production rate of 125 b/d of oil. This was followed by the E.C. Redman/Redman Oil 2 Stevenson (Permit No. 36), which had an initial production of 240 b/d of oil from the Rose Run sandstone.

This significant oil production at shallow depths stimulated leasing and seismic activity in south-central Ohio for Rose Run potential by numerous operators. In Pickaway Township of Pickaway County, NGO Development reported two successful Rose Run completions. The 1 BJM (Permit No. 53) and 2 BJM (Permit No. 59) had initial production rates of 120 b/d and 100 b/d of oil, respectively, at depths of approximately 2,500 ft. In terms of new permits and seismic activity, Pickaway County is currently one of the most active areas in the state.

In nearby Perry Township of Hocking County, Murphy Oil Co. drilled three Rose Run tests of which two were successful completions and one was dry (Fig. 1) (12524 bytes). The Mead (Permit No. 3403) reportedly produced 14,000 bbl of oil during its first 40 days, which averages to 350 b/d. To the north in Madison Township of Perry County, Columbia Natural Resources drilled a successful Rose Run test. The No. 1 Gorsky (Permit No. 7121) blew out and burned for 3 days with an estimated 20 MMcf gas show.5

Another area of active Rose Run exploration is Randolph field in Randolph Township of Portage County in northeastern Ohio (Fig. 1) (12524 bytes). Randolph field was discovered in 1990 with the Belden and Blake 1 Connor Community (Permit No. 3778), which had an initial production of 150 Mcfd of gas and 1 b/d of oil from the Rose Run sandstone. This field appears to be fault-controlled and is situated along the upthrown side of the northwest-southeast trending Akron-Suffield fault system. Average depth to pay is approximately 7,100 ft. Recent Rose Run exploration wells in this area include the Pursie Pipes 2 Danko (Permit No. 3979) and the 1 Hollendonner (Permit No. 3992), which had initial production rates of 200 b/d of oil and 200 Mcfd of gas and 100 b/d of oil and 200 Mcfd of gas, respectively, from the Rose Run. Also of note is the Belden and Blake 3562-001 D'Agostine (Permit No. 3983) which had an initial production rate of 200 b/d of oil and 500 Mcfd of gas.

FUTURE TRENDS

The Rose Run and Beekmantown reservoirs of the Knox play continue to have great potential in Ohio and the adjacent states of the Appalachian basin.

Large areas of the state remain untested for Beekmantown production, particularly within and east of the Rose Run subcrop trend in eastern Ohio and northwestern Pennsylvania.

Rose Run sandstone reservoirs are attractive targets along the entire subcrop trend from south-central Ohio to northeastern Ohio. This trend also extends into and has potential in Rose Run equivalent rocks in northwestern Pennsylvania in the upper sandy member of the Gatesburg formation and western New York in a sandy unit in the Theresa formation. Rose Run and Beekmantown potential also exists in fault-controlled traps along the Akron-Suffield and Highlandtown fault systems in northeastern Ohio. Recent exploration also indicates Rose Run potential exists in structurally-controlled traps east of the subcrop deeper in the basin. Additional exploratory drilling, seismic reconnaissance lines, and advanced geophysical processing and analyses will aid in identifying these subtle Rose Run and Beekmantown stratigraphic and structural traps.

ACKNOWLEDGMENT

I thank J.C. Morgan III for information from the "Ohio Scout Report" presented at the October 1994 Ohio Oil & Gas Association Meeting. I am grateful to Mike McCormac for some of the oil and gas statistics presented in this article. Thanks also go to coworker Mark Baranoski for ideas shared on the Knox, and to Dennis Hull, Ron Rea, and Tom Berg for reviewing this article.

REFERENCES

McCormac, M. P., 1993 Ohio Oil and Gas Developments-"The Debrosse Report," presented at the Ohio Oil & Gas Association winter meeting, Mar. 16, 1993, 1994, 41 p.
Mike McCormac, oral communication, 1994.
Riley, R.A., Harper, J.A., Baranoski, M.T., Laughrey, C.D., and Carlton, R.W., Measuring and predicting reservoir heterogeneity in complex deposystems: the late Cambrian Rose Run sandstone of eastern Ohio and western Pennsylvania, prepared for U.S. Department of Energy, Contract No. DE-AC22-90BC14657, 1993, 257 p.
Baranoski, M.T., Riley, R.A., and Wolfe, M.E., Cambrian-Ordovician Knox unconformity play, in The Atlas of Major Appalachian Gas Plays, prepared for U.S. Department of Energy, Contract No. FC21-91MC28176, in press.
J.C. Morgan 111, oral communication, 1994.