Reservoir Characterizationof the Mancos and the Lewis Shale Gas Plays : Review and Comparison GLGY 703 – Readings in Geology Supervisor : Dr. Per Kent Pederson By : Yulini Arediningsih April 28, 2011 University of Calgary
Outline Background ObjectivesGeology and Reservoir Characteristics Comparison Conclusion
Objectives To review reservoir characterizationparticularly the Mancos shale and the LewisShale within the Rocky Mountain Region. To provide a summary of key reservoirfeatures of the Mancos Shale gas reservoirs
Background The Lewis and Mancos Shales are significantcontributor in gas production of most Rocky Mountainbasins. The Lewis Shale gas play is among the main shalegas producers in the lower 48 states. The Mancos Shale is the second largest shale gasproducers in the Rocky Mountain Region Well defined characteristics on the Lewis Shale. In contrast, geological, geochemical and otherreservoir parameters of the Mancos Shale are still notwell defined.
Major structural features within the Uinta Basin (Osmond et al, 1968)
Stratigraphic section showing the four members of the Mancos Shale in Utah (Ryer, 1984).
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 / Prairie Canyon Juana Lopez Lower Blue Gate Tropic - Tununk Properties Dense, non-fissile, dark Consists of dark gray calcareous Both are made up by detached mudstone and gray claystone with mudstone with interbeds of silt to siltstone succession that are both embeddedLithology scattered, light gray silt very fine sand laminae containing within the Mancos Shale in northeast Utah. laminae and bivalve silt–filled burrows and marker High in quartz content. fragments. bentonite beds.Thickness 1200 ft < 100ft 2000ft 500-825ftPorosity % 2.8 – 11.6 2-5 No data No dataPermeability 0.001 – 0.427 md No data No data No data 0.65 (Estimated fromRo % 0.65 – 1.5 No data No data overlying rock unit) More than 2.0 that might prove to be sweet spots for shaleTOC wt% 1-2 3 gas Potential for natural fracturing due to highNatural quartz content in their siltstone – sandstone Potential for natural and induced fracturingfracturing units
Comparison Similarities : Depositional environments Compared to other Paleozoic prolific shale gas deposits,both contain much lower organic matter and much siltierlithology Both Lewis and Mancos have four members Commingled gas production from other sandstone units. Differences : Lithology Thickness Bentonite Huerfanito Bed in the Lewis Porosity
Parameters Lewis Mancos Various lithology as interbeddedRock lithology Sandy siltstone mudstone, siltstone, and very fine-grained sandstone Four members : The Prairie Four members : the Ute, the Canyon, the Juana Lopez, theMembers Navajo City and the First and Lower Blue Gate and the Tropic- Second of the Otero TununkThickness (feet) 1000-1500 Reaching 4000 2-8Porosity % 2-5Permeability effective gas = 0.1 - 0.00001 Na(md) Average = 0.0001 0.45 to 1.59 with an average of 1 – 2, type II to mixed type II-IIITOC wt% 1.0 kerogen.Maturity (Ro) 1.66 – 1.88 0.65 - 1.5 Always commingle with Always commingle with DakotaProduction Mesaverde and or Dakota and or Castle Gate sandstones sandstones
Conclusion The Mancos Shale is a thick series of fine grained rocks, consistingof interbedded claystone, siltstone, and very fine-grained sandstone,deposited in clastic shoreline to offshore marine environments duringthe Late Cretaceous. The most potential interval for development of the Mancos Shalegas reservoir is the upper part of 3000-3500 ft thick, which largelyrepresents the Prairie Canyon Member. Distribution of Ro values suggests mature areas for oil and gasthroughout the Mancos interval. The Upper Mancos Shale is typicallymature for oil and thermogenic gas whereas the lower part is matureto over mature for oil in most of the basin. Amount of humic (terrigenous) fraction of organic matter containedin the Mancos Shale is controlled by location of deposition of thelithologic sequences with respect to the vegetated shorelines of theSevier belt. Natural fractures are present and identified in the Mancos Shale
Some of the ReferencesCole, 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. 1921–1938Dube, 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 2000EIA, 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, Utahs 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.