# Presentation: 836242

## U.S. Geological Survey Open-File Report 2005-1268Published 2005Online OnlyVersion 1.0Assessment of Undiscovered Natural Gas Resources in Devonian Black Shales, Appalachian Basin, Eastern U.S.A.by Robert C. Milici

**Notes:**
An abbreviated version of this paper was presented at the Annual Meeting of the American Association of Petroleum Geologists at Calgary, Canada, June 20, 2005.

## What do we Assess?

- Technically recoverable undiscovered hydrocarbon resources –
- oil, natural gas, natural gas liquids

**Notes:**
References: Schmoker, J.W., (1995, 1999, 2002).

## The Devonian Shale - Middle and Upper Paleozoic TPS 

- Conventional Oil and Gas Resources
- Accumulations in structural, stratigraphic, combination traps.
- Segregation of fluids within reservoirs (Water, oil, gas cap)

**Notes:**
TPS is “Total Petroleum System.”

## The Devonian Shale - Middle and Upper Paleozoic TPS

- Continuous (unconventional) resources
- Blanket-like accumulations, commonly with multi-storied reservoirs.
- Coalbed methane, Radioactive black shales, tight sandstones -

## How do we do it?

- Conventional: Estimate numbers and sizes of undiscovered fields – maximum, median, minimum, most likely.
- Continuous (unconventional): Estimate numbers of untested cells (40 acres, 80 acres, etc.) and the range of the cumulative production from each cell (max, min, median, mean).

## The Devonian Shale-Middle and Upper Paleozoic TPS (Cont.)

- Continuous Oil and Gas Resources
**Northwestern Ohio Shale (NWOS) AU**
**Greater Big Sandy (GBS) AU**
**Devonian Siltstone And Shale (DSS) AU**
**Marcellus Shale AU**
- Catskill Sandstones and Siltstones AU
- Berea Sandstone AU

**Notes:**
Reference: Milici, and others (2003).  AU is “Assessment unit.”

## The Drake Well: Where it all began

**Notes:**
Reference: U. S. Department of the Interior, undated, Success at Oil Creek: U.S. Department of Interior Historical Vignettes, 1776-1976, 16 p. 

## Slide 8

**Notes:**
This slide shows three of the major orogenic events of the Appalachian basin and their associated petroleum systems, the Iapetan event and the Conasauga-Rome/Conasauge TPS, the Taconic orogeny and the Utica-Lower Paleozoic TPS, and the Acadian orogeny and the Devonian Shale-Middle and Upper Paleozoic TPS (Milici and others, 2003).  The Iapetan event is associated with the Late Precambrian-Early Cambrian opening of the proto-Atlantic Ocean, Iapetus, and the formation of extensional crust in the Appalachian basement, including the Rome Trough. The foreland basin associated with the incipient Taconic orogeny was formed during the Ordovician (Faill, 1997a), and the foreland basin associated with the Acadian orogeny was formed during the Devonian (Faill, 1997b).

## The Devonian Shale-Middle and Upper Paleozoic TPS 

**Notes:**
This slide shows the extent of the Devonian shale in the Appalachian basin. The minimum petroleum system is that area active in the generation and preservation of hydrocarbons.

## Extent and thickness of Devonian rocks in the Appalachian basin (adapted from deWitt and others,1975)

- 12,000 ft

- 25 feet

## Catskill Magnafacies (adapted from Harper, 1999)

**Notes:**
Descriptions generalized from Harper, 1999.  Facies I – Dark colored basinal shales rich in organic matter. Facies II – Interbedded shales and very thin-bedded siltstones, with small amounts of thin bedded fine-grained sandstones; generally deposited as turbidites on the frontal slopes of the deltas.  Facies III – Thin-bedded, fossiliferous marine clastic rocks.  Facies IV – Interbedded varicolored mudrock, shale, siltstone, sandstone, and conglomerate with minor amounts of fossiliferous marine limestone.  Facies V – Generally varicolored non-marine siliciclastic rocks. 

## Extent of Devonian Shale in Eastern U.S. – Section A-A’ (Oliver and others, 1967)

**Notes:**
Location of Cross Section A-A’ from Cherry Valley, New York to Birmingham, Alabama.

## Cross Section A - A’ (de Witt and others, 1975)

- A’

- A

**Notes:**
This section, from de Witt and others, 1975, contains a generalized stratigraphic nomenclature not on the original illustration.  See previous slide for location of section.

## Oil in Devonian Shale and Oriskany Sandstone

**Notes:**
Note that the eastern limit of oil closely follows the 2.0 %Ro line (dispersed vitrinite), whereas the western limit of oil greatly exceeds the 0.6 %Ro isoline.  Work by Rowan and others (2004) has shown that the 0.6 %Ro isoline extends farther to the west in Ohio and may parallel the trend of Devonian isopachs more closely. The 0.6 Ro isolines are from Repetski and others (2002, 2005) and Weary and others (2000).

## Devonian shale assessment units, showing net thickness of radioactive shale

**Notes:**
These are the generalized boundaries of the Devonian shale Assessment Units used by the U.S. Geological Survey for the 2002 assessment of the Appalachian basin. (Milici and others, 2003).  The western boundary of the Northwest Ohio Shale AU is along the 0.6 Ro isoline, based on dispersed vitrinite in the Devonian Shale (Repetski and others, 2002, 2005, and in press; Weary and others, 2000). Basin modeling  by Rowan and others (2004) has shown that much of the area in western Ohio, to the west of the 0.6 % Ro (dispersed vitrinite) is thermally mature with respect to oil generation.  Isopachs are from de Witt and others (1993).

## Greater Big Sandy AU

**Notes:**
Greater Big Sandy Assessment Unit, showing the relationship of the AU to regional geologic structure.  Base map from Ryder and others (in press).  Note that the Greater Big Sandy Assessment Unit is in an area where the Devonian radioactive black shales are relatively thick, thermally mature, and fractured (porous fracture facies of Shumaker (1980). Production from the Devonian shale in the GBS AU is primarily natural gas.

## Cross-Section B - B’ (deWitt and others, 1993)

**Notes:**
See preceding slide for location of cross section. This slide represents part of the cross section B - B’ by deWitt and others (1993).  Generalized location of section is shown in previous slide.  Numbers along top of section correspond to well numbers of deWitt and others (1993).

## Devonian Shale Thickness (deWitt and others, 1993)

**Notes:**
General location of cross section G - G’ of deWitt and others (1993).

## Cross Section G - G’(deWitt and others, 1993)

**Notes:**
This slide represents part of the cross section G - G’ by deWitt and others (1993).  Generalized location of section is shown in previous slide.  Numbers along top of section correspond to well numbers of deWitt and others (1993).  See preceding slide for location of cross section.

## Relation of NWOS to Regional Structure

**Notes:**
Colored areas of closely spaced drilling indicate completions in Devonian shale. Green words indicate general location of stratigraphic decollement in Silurian evaporites and Devonian shale. References: Colton, (1970); Frey, (1973); Shumaker, (1980, 1993,1996); Ryder and others, (in press).  

## Devonian Siltstone and Shale AU

**Notes:**
This slide shows the general relationship of the Devonian Siltstone and Shale Assessment Unit to regional geologic structure. Colored areas of closely spaced drilling indicate completions in Devonian shale. Green words indicate general location of stratigraphic decollement in Silurian evaporites and Devonian shale. References: Colton, (1970); Frey, (1973); Shumaker, (1980, 1993,1996); Ryder and others, (in press).  

## Regional Decollement and Folds

**Notes:**
See previous slide for general levels of decollement in Silurian evaporites and Devonian shale.  Reference: Shumaker (1996).

## Marcellus Shale

**Notes:**
Data from deWitt and others (1993).  Distribution of the Marcellus Shale includes the Millboro Shale in Virginia and West Virginia.  The U.S. Geological Survey’s assessment was based upon the distribution of the relatively thick shale in Pennsylvania and West Virginia.

## EUR distribution: Greater Big Sandy AU by thirds 

**Notes:**
Note that the EUR (Estimated Ultimate Recovery) distribution for the latest third has declined a little from that of the middle third. This indicates that EUR distributions from future wells may be lower than that for existing wells.

## EUR distribution: NWOS AU by thirds

**Notes:**
The location of the Late Average third at or near the top of the sequence of curves suggests that, with improved completion technology, EURs for future wells may exceed those shown in this slide.

## EUR distribution: DSS by Thirds

**Notes:**
EUR distributions in this assessment unit show a general decline with time.

## Undiscovered Resources

**Notes:**
This slide combines resource estimates from Milici and others (2003) with the areas of the Assessment Units, Ro isotherms, and the distribution of oil and gas accumulations.

## Per Well Estimates of Technically Recoverable Gas (DOE EGSP)

**Notes:**
This slide is compiled from data published by Kuuskraa and Wicks, 1984; Kuuskraa and others, 1985; and Lewin and Associates, Inc., 1983.  Well  spacing assumptions range from 80 acres in the area of productive black shale in eastern Kentucky to 160 acres in the area of limited production.  In West Virginia, well spacing was assumed as 80 acres, and in Ohio, as 160 acres.  At present, wells are commonly drilled on 20 to 40 acre-spacing in the Greater big Sandy Assessment Unit.

## Selected References

- Boswell, Ray, 1996, Play UDs: Upper Devonian black shales, *in* Roen, J.B., and Walker, B.J., 1996, The Atlas of Major Appalachian Gas Plays: West Virginia Geological and Economic Survey Publication V-25, p. 93-99.
- Colton, G.W., 1970, The Valley and Ridge and Appalachian Plateau; stratigraphy and sedimentation; the Appalachian basin; its depositional sequences and their geologic relationships, *in* Fisher, George W., Pettijohn, F.J., and Reed, J. C., Jr., Studies of Appalachian Geology, Central and Southern: Interscience Publishers, New York, N.Y., p. 5-47.
- Charpentier, R.R., deWitt, Wallace, Claypool, G.E., Harris, L.D., Mast, R.F., Megeath, J.D., Roen, J.B., and Schmoker, J.W., 1993, Estimates of unconventional natural gas resources of the Devonian shales of the Appalachian basin, *in* Roen, J.B., and Kepferle, R.C., 1993, Petroleum geology of the Devonian and Mississippian black shale of eastern North America: U.S. Geological Survey Bulletin 1909B, p. N1-N 20.
- deWitt, Wallace, Jr., Perry, W.J., Jr., and Wallace, L.G., 1975, Oil and gas data from Devonian and Silurian rocks in the Appalachian basin: U.S. Geological Survey Miscellaneous Investigations Series Map I-917 B, scale: 1:2,500,000.
- deWitt, Wallace, Jr., Roen, J.B., and Wallace, L. G., 1993, Stratigraphy of Devonian black shales and associated rocks in the Appalachian basin, *in* Roen, J.B., and Kepferle, R.C., 1993, Petroleum geology of the Devonian and Mississippian black shale of eastern North America: U.S. Geological Survey Bulletin 1909B, p. B1-B57.
- Faill, R.T., 1997a, A geologic history of the north-central Appalachians, part 1.  Orogenesis from the mesoproterozoic through the Taconic orogeny: American Journal of Science, v. 297. p. 551-619.
- Faill, R.T., 1997b, A geologic history of the north-central Appalachians, part 2.  The Appalachian basin from the Silurian through the Carboniferous: American Journal of Science, v. 297. p. 729-761.
- Frey, M. G., 1973, Influence of Salina salt on structure in New York-Pennsylvania part of the Appalachian Plateau: American Association of Petroleum Geologists Bulletin, v. 57, no. 6, p. 1027-1037.
- Harper, J.A., 1999, Chapter 7, Devonian, *in* Schultz, C.H., ed., The Geology of Pennsylvania, p. 129-137.
- Kuuskraa, V.A., and Wicks, D. E., 1984, Technically recoverable Devonian Shale gas in West Virginia:  U.S. Department of Energy
- Morgantown Energy Technology Center DOE/MC/19239-1750 (DE85003367), 119 p.
- Kuuskraa, V.A., Sedwick, K.B., Thompson, K.B., and Wicks, D. E., 1985, Technically recoverable Devonian Shale gas in Kentucky:  U.S.
- Department of Energy Morgantown Energy Technology Center DOE/MC/19239-1834 (DE85008608), 120 p.
- Lewin and Associates, Inc., 1983, Technically recoverable Devonian Shale gas in Ohio:  U.S. Department of Energy Morgantown Energy
- Technology Center DOE/MC/19239-1525 (DE84003057), 101 p.
- Lundegard, P.D., Samuels, N.D., and Pryor, W. D., 1985, Upper Devonian turbidite sequence, central and southern Appalachian basin:
- contrasts with submarine fan deposits, *in* Woodrow and Sevon, eds., The Catskill delta: Geological Society of America Special Paper 201, p. 107-121.
- Milici, R.C., 1993, Autogenic gas (self-sourced) from shales- An example from the Appalachian basin, *in* Howell, D.G., ed., The future of
- energy gases: U.S. Geological Survey Professional Paper 1570, p. 253-278.

## References (Cont.)

- Milici, R.C., 1996, Play Dbg: Upper Devonian fractured black shales and siltstones,* in* Roen, J.B., and Walker, B.J., 1996, The Atlas of Major Appalachian Gas Plays: West Virginia Geological and Economic Survey Publication V-25, p. 86-92.
- Milici, R.C., 2005,  Assessment of undiscovered natural gas resources in Devonian black shales, Appalachian basin, eastern U.S.A.:  American
- Association of Petroleum Geologists Abstracts Volume for the 2005 Annual Convention, p. A93.
- Milici, R.C. and Statler, 1980, fractures related to major thrusts – possible analogues to tectonically fractured Chattanooga Shale in Tennessee: *in*
- Wheeler, R.L., and Dean, C.S., eds., Proceedings western limit of detachment and related structures in the Appalachian foreland: U.S.
- Department of Energy Morgantown Energy Technology Center DOE/METC/SP-80/23, p.157-166.
- Milici, R.C., Ryder, R.T., Swezey, C.S., Charpentier, R.R., Cook, T. A., Crovelli, R.A., Klett, T.R., Pollastro, R.M., and Schenk, C.J., 2003,
- Assessment of undiscovered oil and gas resources of the Appalachian Basin Province, 2003: U.S. Geological Survey Fact Sheet FS-009-03, 2 p.
- Oliver, W.A., Jr.; deWitt, Wallace, Jr.; Dennison, J.M.; Hoskins, D.M.; and Huddle, J. W., 1967, Devonian of the Appalachian Basin, United
- States, *in* Oswald, G.H., ed., International Symposium on the Devonian System: Alberta Society of Petroleum Geologists, Calgary, Alberta, p.
- 1001 - 1040.
- Oliver, W.A., Jr.; deWitt, Wallace, Jr.; Dennison, J.M.; Hoskins, D.M.; and Huddle, J. W., 1971, Isopach and lithofacies maps of the Devonian in
- the Appalachian Basin: Pennsylvania Bureau of Topographic and Geologic Survey Progress Report 182.
- Repetski, J.E.., Ryder, R.T., Harper, J.A., and Trippi, M.H., 2002, Thermal maturity patterns in the Ordovician and Devonian rocks of the
- Appalachian basin in Pennsylvania: U.S. Geological Survey Open-File Report 02-302, 57 p.
- Repetski, J.E.., Ryder, R.T., Avary, K.L., and Trippi, M.H., 2005, Thermal maturity patterns (CAI and %Ro) in the Ordovician and Devonian rocks
- of the Appalachian basin in West Virginia: U.S. Geological Survey Open-File Report 2005-1087, 69 p.
- Ryder, R.T., Swezey, C.S., Crangle, R.D., Jr., and Trippi, M.N., in press, Geologic cross section through the central Appalachian basin from the
- Findlay arch, Wood County, Ohio, to the Allegheny structural front, Pendleton County, West Virginia: U.S. Geological survey Scientific
- Investigations Map I-XX.
- Roen, J.B. and Kepferle, R.C., eds., 1993, Petroleum geology of the Devonian and Mississippian black shale of eastern North America: U.S.
- Geological Survey Bulletin 1909.
- Roen, J. B., and Walker, B.J., 1996, The atlas of major Appalachian gas plays: West Virginia Geological and Economic Survey Publication
- V-25, 201p.
- Rowan, E. L., Ryder, R.T., Repetski, J.E., Trippi, M.H., and Ruppert, L.F., (2004), Initial results of a 2d burial/thermal history model through the c
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## References (Cont.)

- Schmoker, J.W., 1995, Method for assessing continuous-type (unconventional) hydrocarbon accumulations, *in* Gautier, D.L., Dolton, G.L.,
- 	Takahashi, K.I., and Varnes, K.L., eds., 1995 national assessment of United States oil and gas resources-results, methodology, and
- 	supporting data: U.S. Geological Survey Digital Data Series DDS-30, 1 CD-ROM.
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- 	model: U.S. Geological Survey Bulletin 2168, <http:// greenwood.cr.usgs.gov> Accessed December 1999.
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- 	Bulletin, v. 86, no. 11, p. 1993-1999.
- Shumaker, R.C., 1980, Porous fracture facies in Devonian shales of eastern Kentucky and West Virginia: *in* Wheeler, R.L., and Dean, C.S., eds., Proceedings western limit of detachment and related structures in the Appalachian foreland: U.S. Department of Energy
- 	Morgantown Energy Technology Center DOE/METC/SP-80/23, p.124-132.
- Shumaker, R.C., 1993, Structural parameters that affect Devonian Shale gas production in West Virginia and eastern Kentucky, *in* Roen, J.B.,
- 	and Kepferle, R.C., 1993, Petroleum geology of the Devonian and Mississippian black shale of eastern North America: U.S. Geological
- 	Survey Bulletin 1909B, p. K1-K38.
- Shumaker, R.C., 1996, Structural history of the Appalachian basin, *in* Roen, J.B., and Walker, B.J., 1996, The Atlas of Major Appalachian Gas
- 	Plays: West Virginia Geological and Economic Survey Publication V-25, p. 8-21.
- U. S. Department of the Interior, undated, Success at Oil Creek: U.S. Department of Interior Historical Vignettes, 1776-1976, 16 p.
- Van Tyne, A. M., Play SBI: Upper Silurian Bass Islands Trend, *in* Roen, J.B., and Walker, B.J., 1996, The Atlas of Major Appalachian Gas
- 	Plays: West Virginia Geological and Economic Survey Publication V-25, p. 130-132.
- Weary, D.J., Ryder, R.T., and Nyahay, R.E., 2000, Thermal maturity patterns (CAI and %Ro) in the Ordovician and Devonian of the Appalachian basin in New
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