MODERN DEVONIAN SHALE GAS SEARCH STARTING IN SOUTHWESTERN INDIANA

Feb. 27, 1995
Edward D. Minihan , Ray D. Buzzard Consulting petroleum geologists Fort Worth The New Albany shale of southwestern Indiana is a worthwhile exploration and exploitation objective. The technical ability to enhance natural fractures is available, the drilling depths are shallow, long term gas reserves are attractive, markets are available, drilling costs are reasonable, risks are very low, multiple drilling objectives are available, and the return on investment is good. Indiana Geological Survey
Edward D. Minihan, Ray D. Buzzard
Consulting petroleum geologists
Fort Worth

The New Albany shale of southwestern Indiana is a worthwhile exploration and exploitation objective. The technical ability to enhance natural fractures is available, the drilling depths are shallow, long term gas reserves are attractive, markets are available, drilling costs are reasonable, risks are very low, multiple drilling objectives are available, and the return on investment is good.

Indiana Geological Survey records are well organized, accessible, and easy to use.

NEW ALBANY SHALE PLAY

During a span of time, composed of the Mississippian (Kinderhookian) and the Devonian (Chautauquan, Senecan, and Erian) shale was being deposited in a vast sea that covered a large portion of the eastern and central U.S., including the area of interest in southwestern Indiana (Fig. 1).

This shale has many names. Aside from local names, drillers referred to it as the "Black shale," and "Brown shale," or the "Devonian shale." Regionally the shale sequence is called the Ohio shale in Ohio and Kentucky, Milborn shale in Virginia, the Chattanooga shale in Alabama, Mississippi, Tennessee, Kentucky, and West Virginia, Woodford shale in Oklahoma and Texas, Percha shale in New Mexico, Antrim shale in Michigan, and New Albany in Illinois, Missouri, western Kentucky, and Indiana.

While no accurate recent count of the number of acres leased in the play is available, the authors believe the figure exceeds 100,000 acres.

Seminole Land & Cattle Co., Seminole, Okla., and Citizens Gas & Coke Utilities, Indianapolis, have scheduled a five well program in Green County. William Leidtke, Oklahoma City, has a three well drilling program in Green County.

Deka Exploration Inc., Oklahoma City, has drilled four wells in Jackson, Daviess, and Martin counties, Ind., and Dart Oil & Gas Corp., Mason, Mich., has drilled two wells in Warrick County, Ind.

Independent operators are conducting most of the current exploration. The active counties as known to the authors are Lawrence, Harrison, Orange, Jackson, Washington, Crawford,

Daviess, Martin, Green, and Warrick (Fig. 2).

PLAY SIZE, EARLY EXPLORATION

Several thousand wells have been drilled in the Devonian Antrim shale gas play in Michigan.1 This activity, coupled with an increase in Antrim lease costs, has created an interest in the New Albany shale in Indiana where the shale has produced in the past.

The National Petroleum Council Committee on Unconventional Gas Sources Devonian Shale Task Group has estimated gas content of the New Albany shale in the Illinois basin at 86 tcf based on 0.62 cu ft of gas/cu ft of shale (Fig. 3).2 3

"Gas springs" were noted in the bed of the Ohio River in Indiana in 1870, and in 1885 drilling for New Albany shale gas began in Harrison County, Ind.4 By 1925 seven fields were producing gas from the New Albany shale in the county.

The early phase of New Albany shale gas exploration and production in Indiana ended because of significant regional competition from an abundant supply of gas being produced from Mississippian carbonate reservoirs in eastern Kentucky.

Depth to the top of the New Albany in Indiana in the producing gas fields varies from 300 ft in Rosewood field in Harrison County to 3,400 ft in Yankeetown field in Warrick County. The range of average reported initial potential values for the fields varies from 8 Mcfd in Duff field, Dubois County, to 4.4 MMcfd in Dickeyville field in Warrick County 2 (Fig. 2).

All of the Harrison County wells produced salt water along with the gas, sometimes in amounts sufficient to cause the flow of gas to cease.5 The average life of a commercial gas well in Harrison County was about 20 years. Some wells lasted for a much longer time, but the production was not of commercial quantity. The majority of the wells that were shut in were still capable of producing 10-30 Mcfd; however, because of salt water the wells could not be operated economically5 (Fig. 2).

Loogootee North field in Martin County yielded gas from as many as 12 of 19 wells, but as of 1981 it contained only one domestic gas well. Gas was first produced from a well in 1902; however, data are lacking for the producing formation, the completion interval, and the TD of this well.

The other 11 wells in the field were drilled between 1948 and 1953 and are known to have produced gas from the New Albany shale. Gas was found in the upper 50 ft of the shale at a depth of about 1,500 ft, and a maximum gas flow was from a zone about 30 ft from the top of the shale. At a depth greater than about 50 ft into the shale salt water generally was encountered5 (Fig. 2).

The field wells were cased to the Rockford limestone, drilled into the New Albany shale or underlying Devonian limestone, and completed open hole with gelatinated nitroglycerine shot stimulation. After the wells were shot the open hole flow rates reportedly increased threefold.

The last three wells drilled in the field were completed only in the upper 40 ft of the shale, thus avoiding most of the salt water. Initial potentials ranged from 200 Mcfd to 2 MMcfd, and the field average IP was 780 Mcfd (Fig. 2).

GEOLOGIC SETTING

A structure map of Loogootee North field on top of the New Albany shale shows a structural depression5 (Fig. 2).

A prominent feature in Indiana is the Mt. Carmel fault, which trends north-northwest for about 50 miles from northern Washington County to northern Monroe County in south-central Indiana (Fig. 4). The fault is a normal fault, downthrown to the west, with a maximum vertical displacement of 200 ft.6 Seismic data indicate the Mt. Carmel fault reaches basement.6 Rudman and others' noted a change in the gradient of the basement surface and suggest the fault marks the hinge line of the Indiana-Ohio platform and the Illinois basin (Fig. 4).

Numerous pinnacle reefs and pinnacle-reef complexes of Silurian age are present in the subsurface of southwestern Indiana and eastern Illinois and have been interpreted as non-tectonic structures. In southwestern Indiana numerous reefs are present along the Terre Haute bank in Clay, Daviess, Dubois, Green, Owen, Spencer, Sullivan, and Virgo counties.2 8

Throughout southwestern Indiana the New Albany unconformably overlies the North Vernon limestone (Middle Devonian) of the Muscatatuck group.2

The New Albany shale is overlain by the Rockford limestone (kinderhookian to Lower Valmeyeran) in much of Indiana9 but can be absent locally.

Individual stratigraphic units within the New Albany shale from the bottom are the Blocher member, Selmier member, Morgan Trail member, Camp Run member, Clegg Creek member, and Ellsworth member. The New Albany dips and thickens into the Illinois basin, interrupted only by faulting and/or closure, from the outcrop in a southwesterly direction (Figs. 2, 5).

Ault 8 concluded:

1. That the primary joints generally trend northeast to southwest.

2. The secondary joints generally trend northwest to southeast, are more variable, abut primary joints, usually confined to an area between primary joints, and are shorter than primary joints.

3. The vertical extent of jointing ranges from a few inches to the full extent of the New Albany, and

4. Although the amount of communication among the units is unknown, movements of considerable volumes of fluid and gases may be possible.

The New Albany shale, organic-rich, brown to black, highly fractured, and radioactive, was deposited in deep waters in a tropical climate near the equator where anoxic conditions existed. The lack of oxygen precluded the existence of burrowing macrofauna and restricted the microbial flora to anaerobes. Abundant organic matter was preserved in the sediments, resulting in the thick accumulation of black shale.10

Bond et al.11 cited the New Albany shale, the thickest, most widespread continuous organic rich unit in the Illinois basin, as a potential source rock on the basis of organic carbon content alone.

Lineback 12 reported organic contents as high as 20% by weight in some members of the New Albany shale. Because of its high organic content, the black shale facies tends to have high concentrations of radioactive elements such as uranium and thorium. These concentrations cause "hot" zones on natural gamma ray logs, in some cases 200-400 AP1 units above normal shale background (Fig. 6).

Aside from the current ongoing commercial development of the fractured Antrim shale in Michigan, commercial production from the fractured Ohio shale and the Chattanooga shale are found in Kentucky and West Virginia. In a giant field called Big Sandy, recovery greater than 4 tcf is anticipated from more than 6,000 wells.

Total organic carbon (TOC) in the Antrim shale in Michigan is approximately 6-7% by weight. In southwestern Indiana the New Albany shale has an approximate TOC of 8-10% by weight (Fig. 6).

COMPLETION TECHNIQUES

Successful completion techniques have evolved in the development of the Antrim shale in Michigan and they should be studied and employed in the development of the New Albany shale in Indiana. It is certain that modified and newer techniques will evolve in Indiana that work best for the area.

The New Albany shale, as the Antrim shale does, will produce salt water, and any drilling and development program should have a disposal well as an integral part of development cost.

Structure is not necessary for gas accumulation in the New Albany shale.2 Stimulation is necessary to acquire commercial rates and to capture all the gas available to the well bore. Stimulation will interconnect the well bore with the natural fracture system. Effective stimulation maintains permeability by introducing a proppant into the pressure sensitive fractures near the well bore.2

LOCATING PRIME AREAS

It is the job of a geologist to find the area of the most effective fractures in order to make the best completions for his company. In certain areas, the authors believe, any well can be completed as a gas well in the New Albany shale, but there will be area 11 sweet spots" and these require the geological search.

New Albany shale gas is predominantly methane with significant and variable amounts of heavier hydrocarbons. This gas is found as free gas in open pore space and as adsorbed gas in interior clay and kerogen surfaces.2

Several oil bearing Mississippian formations must be penetrated in any New Albany shale test that are stratigraphic in nature.

Development of a New Albany shale field will provide much control for locating these shallow stratigraphic producing formations.

Devonian carbonates below the New Albany shale are also productive, and normally evidence of closure is reflected in the shale.

ACKNOWLEDGMENTS

The Indiana, Illinois, and Kentucky Geological Surveys have published many excellent papers on the New Albany shale. This article is based mostly on the most recent publication, Gas Research Institute 92/0391.2

REFERENCES

1. Antrim gas play, production expanding in Michigan, OGJ, May 30,1994, p. 97.

2. Comer, I.B., Hasenmueller, N.R., Frankie, W.T., Hamilton-Smith, T., Lumm, D.K., Boberg, W. S., and Smidchens, Z., Gas potential of the New Albany shale (Devonian and Mississippian) in the Illinois basin, Gas Research Institute, Illinois Basin Studies 2, GRR 92/0391,1992.

3. Bookout, J.F., Unconventional gas sources-Vol. III, Devonian Shales, National Petroleum Council Committee on Unconventional Gas Sources, 1980.

4. Collett, J., Geological report on Harrison and Crawford counties, Ind, Indiana Geological Survey annual reports 8, 9, and 10, 1879, pp. 291-522.

5. Sorgenfrei, H. Jr., Gas production from the New Albany shale, Bloomington, Indiana University, master's thesis, 1952, 26 p.

6. Sullivan, D.M., Ault, C.H., and Tanner, G.F., Mt. Carmel fault in south-central Indiana, in Ault, C.H., and Sullivan, D.M., eds., Faulting in southwest Indiana, U.S. Nuclear Regulatory Commission, NUREG/CR-2908,1982, pp. 34-41.

7. Rudman, A.J., Summerson, C.H., and Hinze, W.J., Geology of basement in Midwestern U.S., AAPG Bull., Vol. 49,1965, pp. 894-904.

8. Ault, Curtis H., Directions and characteristics of jointing in the New Albany shale (Devonian-Mississippian) of southeastern Indiana, in proceedings, 1989 Eastern Oil Shale Symposium, University of Kentucky, Lexington, Kentucky Center for Applied Energy Research, IMMR89/201, 1990, pp. 239-252.

9. Rexroad, C.B., and Scott, A.J., Conodont zones in the Rockford limestone and the lower part of the New Providence shale (Mississippian) in Indiana, Indiana Geological Survey Bull. 30,1964, 54 p.

10. Barrows, Mary H., and Cuff, Robert M., New Albany shale group (Devonian-Mississippian) source rock and hydrocarbon generation in the Illinois basin, in Demaison, G., and Murris, R.J., eds., Petroleum geochemistry and basin evaluation, AAPG Memoir 35, pp. 1984, pp. 111-138..

11. Bond, D.C., et al., Possible future petroleum potential of Region 9-Illinois basin, Cincinnati arch, and northern Mississippian embayment, in Cram, I.H., ed., Future petroleum provinces of the U.S.-their geology and potential, AAPG Memoir 15, Vol. 2, 1971, pp. 1,165-1,218.

12. Lineback, J.A., Stratigraphy of the New Albany shale in Indiana, Indiana Geological Survey Bull. 44, 1970, 73 p.

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