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PSGenesis and Expression of a Clinoforming Carbonate Ramp from a Geological and Geophysical Perspective*
Jean-Yves Chatellier1, Jeff Closson1 and Anne Hargreaves2
Search and Discovery Article #50148 (2009)
Posted January 26, 2009
*Adapted from oral presentation at AAPG Annual Convention, San Antonio, TX, April 20-23, 2008
1Talisman Energy Inc., Calgary, AB, Canada ([email protected])
2Canadian Stratigraphic Services 2000 Ltd, Calgary, AB, Canada
Progradation in a carbonate ramp is not always well
expressed in
seismic or in geological cross sections. Clinoforms in the Carboniferous Banff
Formation (Alberta,
Canada) have been studied in an integrated approach using
log
analysis
,
sedimentology and seismic data. The genesis and geometry of several clinoforms
have been examined against their structural settings. Cutting descriptions from
Canstrat have been used to better understand the sedimentology and lithologies
above and below the clinoforming surfaces.
In the
Western
Alberta Basin, the Carboniferous Banff Formation is a prograding carbonate ramp
with some very well
developed clinoforms. Three main types of clinoforming
surfaces have been recognized on wireline logs in association with transgressive
shales, slump related chert units or catastrophic grain supported carbonate
events. The seismic expression associated with the carbonate ramp has been
tested against lateral facies variations.
Synthetic seismograms have been generated on many wells from a
variety of clinoforms in order to determine if and when a progradation would be
seen on seismic. A comparison between two geographically distinct clinoforms
with apparently identical log
expressions has outlined extreme differences in
their potential to be seismically visible. The structural context favorable to
recognizable clinoforming pattern is variable and the direction of progradation
may vary dramatically especially when alternate fault activity is
syndepositional. One example shows two successive clinoforming patterns at 90
degrees from each other within the
Lower Banff.
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Banff Formation: A Prograding Carbonate Ramp (Figures 3, 4, 5, 6, 7, 8, 9 and 10)
Banff Clinoform Case Example 2
Alternate Fault Activity Controlled Two Successive Carbonate Ramp Progradations
· The expression of clinoforms is highly variable. · On logs:
o
o Major shaly transgressive events are outstanding markers. · Seismic expression versus lithology: o No clear-cut relationship has been found based on cuttings description.
o
Cherty units and bases of gradual coarsening up · On Seismic cross section: o Frequency is a very critical parameter (40 Hz being a limit). o Depth is a major controlling factor to the frequency of the signal. · On seismic horizon/time slices: o Repetition of parallel and long linear features is a common characteristic of clinoforming settings. Chatellier, J-Y., 1988, Carboniferous Carbonate Ramp, The Banff Formation, Alberta, Canada, Bull. Centre Rech. Explor. Prod. Elf-Aquitaine, Vol. 12-2, p. 569-599.
Chatellier, J-Y., 2004, Chert, a diagenetic and sedimentological indicator often underused, Mississippian examples from Alberta and world analogues, CSPG convention 2004, Calgary, 10 page extended abstract http://www.cspg.org/conventions/abstracts/2004abstracts/066S0129.pdf.
Chatellier,
J-Y. and Porras C., 2004, The Multiple Bischke Plot
Chatellier, J-Y., 2008, Fault locking and alternate activity in outcrops and subsurface, a transfer mechanism, AAPG Annual Convention, San Antonio, Abstract.
Grelaud, C., 2005, Enregistrement stratigraphique des phases d’emersion sur les plate-formes carbonatees, Unpublished PhD thesis, Bordeaux III University, 285 pages.
Handford, C.R. and Baria, L.R., 2007, Geometry and seismic geomorphology of carbonate shoreface clinoforms, Jurassic Smackover Formation, north Louisiana, Geological Society, London Special Publications, vol. 277, p.171-185.
The authors would like to thank Talisman Energy Inc. for permission to present this material and Canadian Stratigraphic Services (2000) Ltd for providing the needed cuttings description. They also want to thank Gary Labute for his support of this project
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