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.
· The expression of clinoforms is highly variable.
· On logs:
o Log facies map are incredibly powerful at displaying progradation patterns.
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 sequence seem best.
· 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.
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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
Chatellier, J-Y. and Porras C., 2004, The Multiple Bischke Plot Analysis, a Simple and Powerful Graphic Tool for Integrated Stratigraphic Studies, AAPG Search and Discovery Article #40110 (2004), http://www.searchanddiscovery.com/documents/2004/chatellier/index.htm.
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