Reservoir Characterization of the Mancos and the Lewis Shale Gas Plays :

Review and Comparison

GLGY 703 – Readings in GeologySupervisor : Dr. Per Kent Pederson

By : Yulini Arediningsih

April 28, 2011University of Calgary

Background

Objectives

Geology and Reservoir Characteristics

Comparison

Conclusion

Outline

To review reservoir characterization particularly the Mancos shale and the Lewis Shale within the Rocky Mountain Region.

To provide a summary of key reservoir features of the Mancos Shale gas reservoirs

Objectives

The Lewis and Mancos Shales are significant contributor in gas production of most Rocky Mountain basins.

The Lewis Shale gas play is among the main shale gas producers in the lower 48 states.

The Mancos Shale is the second largest shale gas producers in the Rocky Mountain Region

Well defined characteristics on the Lewis Shale.

In contrast, geological, geochemical and other reservoir parameters of the Mancos Shale are still not well defined.

Background

(EIA, 2010 http://www.eia.gov/oil_gas/rpd/shale_gas.pdf Retrieved 8/3/2011)

Stratigraphic section showing Upper Cretaceous rocks including the Lewis Shale in the San Juan Basin (New Mexico and Colorado)

(Fassett, 2009)

From Curtis, 2002

Major structural features within the Uinta Basin

(Osmond et al, 1968)

(Ryer, 1984).

Stratigraphic section showing the four members of the Mancos Shale in Utah

Stratigraphic from GR log of the Mancos Shale members over the Douglas Creek Arch

(Cole et al, 1997).

The Members of the Mancos

Shale

Members / Properties

Prairie Canyon Juana Lopez Lower Blue Gate Tropic - Tununk

Lithology

Both are made up by detached mudstone and siltstone succession that are both embedded within the Mancos Shale in northeast Utah. High in quartz content.

Dense, non-fissile, dark gray claystone with scattered, light gray silt laminae and bivalve fragments.

Consists of dark gray calcareous mudstone with interbeds of silt to very fine sand laminae containing silt–filled burrows and marker bentonite beds.

Thickness 1200 ft < 100ft 2000ft 500-825ft

Porosity % 2.8 – 11.6 2 - 5 No data No data

Permeability 0.001 – 0.427 md No data No data No data

Ro % 0.65 – 1.5 No data0.65 (Estimated from overlying rock unit)

No data

TOC wt% 1-2 3More than 2.0 that might prove to be 'sweet spots' for shale gas

Natural fracturing

Potential for natural fracturing due to high quartz content in their siltstone – sandstone units

Potential for natural and induced fracturing

Similarities : Depositional environments Compared to other Paleozoic prolific shale gas deposits, both contain much lower organic matter and much siltier lithology Both Lewis and Mancos have four members Commingled gas production from other sandstone units.

Differences : Lithology Thickness Bentonite Huerfanito Bed in the Lewis Porosity

Comparison

Parameters Lewis Mancos

Rock lithology Sandy siltstoneVarious lithology as interbedded mudstone, siltstone, and very fine-grained sandstone

MembersFour members : the Ute, the Navajo City and the First and Second of the Otero

Four members : The Prairie Canyon, the Juana Lopez, the Lower Blue Gate and the Tropic-Tununk

Thickness (feet) 1000-1500 Reaching 4000

Porosity %

2 - 8

2 - 5

Permeability (md)

effective gas = 0.1 - 0.00001Average = 0.0001

Na

TOC wt%0.45 to 1.59 with an average of 1.0

1 – 2, type II to mixed type II-III kerogen.

Maturity (Ro) 1.66 – 1.88 0.65 - 1.5

ProductionAlways commingle with Mesaverde and or Dakota sandstones

Always commingle with Dakota and or Castle Gate sandstones

The Mancos Shale is a thick series of fine grained rocks, consisting of interbedded claystone, siltstone, and very fine-grained sandstone, deposited in clastic shoreline to offshore marine environments during the Late Cretaceous.

The most potential interval for development of the Mancos Shale gas reservoir is the upper part of 3000-3500 ft thick, which largely represents the Prairie Canyon Member.

Distribution of Ro values suggests mature areas for oil and gas throughout the Mancos interval. The Upper Mancos Shale is typically mature for oil and thermogenic gas whereas the lower part is mature to over mature for oil in most of the basin.

Amount of humic (terrigenous) fraction of organic matter contained in the Mancos Shale is controlled by location of deposition of the lithologic sequences with respect to the vegetated shorelines of the Sevier belt.

Natural fractures are present and identified in the Mancos Shale

Conclusion

Some of the References

Cole, R.D., R.G. Young, and G.C. Willis, 1997, The Prairie Canyon Member, a new unit of the Upper Cretaceous Mancos Shale, west-central Colorado and east-central Utah: Utah Geological Survey Miscellaneous Publication 97-4, 23 p.

Curtis, J.B., 2002, Fractured shale-gas systems, AAPG Bulletin, v. 86, no. 11 (November 2002), pp. 1921–1938

Dube, H.G. , Christiansen, G.E., Frantz, J.H., Fairchild, N.R., Olszewski, A.J., Sawyer, W.K., and Williamson, J.R., 2000, The Lewis Shale, San Juan Basin: What We Know Now : SPE 63091, prepared for presentation at the 2000 SPE Annual Technical Conference and Exhibition held in Dallas, Texas, 1–4 October 2000

EIA, 2010, Map of shale gas plays, Lower 48 States, updated June 2010. Online: http://www.eia.doe.gov/oil_gas/rpd/shale_gas.pdf (Retrieved on 2011-04-12)

Fassett, J.E., 2000, Chapter Q: Geology and Coal Resources of the Upper Cretaceous Fruitland Formation, San Juan Basin, New Mexico and Colorado in Geologic Assessment of Coal in the Colorado Plateau: Arizona, Colorado, New Mexico, and Utah, M.A. Kirschbaum, L.N.R. Roberts, and L.R.H. Biewick (editors), Professional Paper 1625–B* U.S. Geological Survey.

Fisher, D.J., Erdmann, C.E., and Reeside, J.B., Jr., 1960, Cretaceous and Tertiary Formations of the Book Cliffs, Carbon, Emery, and Grand Counties, Utah, and Garfield and Mesa Counties, Colorado: U.S. Geological Survey Professional Paper 332, 80 p.

Osmond, J.C.,1968, Natural gas in Uinta Basin, Utah, in Natural gases of North America - pt. 1, Natural gases in rocks of Cenozoic age: Am. Assoc. Petrol. Geol. Mem. 9, v. 1, p. 174-198.

Ryer, T. A., 1984, Transgressive-regressive cycles and the occurrence of coal in some Upper Cretaceous strata of Utah, U.S.A., in R. A. Rahmani, and R. M. Flores, ds., Sedimentology of Coal and Coal-bearing Sequences. International ssociation of Sedimentologists Special Publication 77, Oxford, UK, Blackwell cientific, p. 217-227.

Schamel, S., 2005, Shale Gas Reservoirs of Utah: Survey of an Unexploited Potential Energy Resource, an Open file, A report for the Utah Geological Survey State. Online http://ugspub.nr.utah.gov/publications/open_file_reports/OFR-461.pdf (Retrieved on 2011-04-21)

Schamel, S., 2006, Shale gas reservoirs of Utah: assessment of previously underdeveloped gas discoveries: Utah Geological Survey OFR 499.

Willis, G.C., 2000, Utah's Sevier Thrust System, Survey Notes article, v. 32 no. 1 January 2000, Online http://geology.utah.gov/utahgeo/geo/thrustfault.htm#system , retrieved April 26, 2011.

Thank you

Modified from Willis (2000) http://geology.utah.gov/utahgeo/geo/thrustfault.htm#system