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3-D Modelling of Epeiric 
Carbonate
Reservoirs: A Workflow from Outcrop to Streamline Simulation*
Denis Palermo1, Thomas Aigner2, Sergio Nardon1, and Wolfgang Blendinger3
Search and Discovery Article #50092 (2008)
Posted October 3, 2008
*Adapted from oral presentation at AAPG Annual Convention, San Antonio, Texas, April 20-23, 2008.
1 Sedimentology, Petrography and Stratigraphy, ENI S.p.A. - Exploration& Production Division, San Donato Milanese, Italy ([email protected])
2 Sedimentary Geology, University of Tübingen, Tuebingen, Germany
3 Petroleum Geology, Technical University of Clausthal, Clausthal-Zellerfeld, Germany
Within the GECO-project, a joint ENI E&P - University research consortium on the “Geometry of Carbonate Objects,” Triassic epicontinental ramp carbonates in the South-German Basin were studied as an analog to “non reefal” carbonate sand reservoirs of the Middle East. The reservoir facies consists of skeletal and oolitic carbonate pack- and grainstones (Phi max. 23%, K max 700 mD), organised in a three-fold hierarchy of cycles. The purpose of this study is a detailed analysis of the evolution, anatomy, sedimentology, and petrophysical characteristics of the reservoir bodies. The database consists of 50 measured sections supplemented by 6 cores and wireline logs as well as 568 poroperm plugs and covers an area at the scale of a giant gas-field (25x36 km). To link the study directly with the subsurface, all data have been compiled in a high-resolution 3D geological reservoir model, using the software Petrel.
The outcrop analog study demonstrated that the apparently “layer-cake” stratigraphy shows in fact subtle clinoform geometries.
Key factors controlling the reservoir distribution and properties are:
a) Facies and early diagenesis: Porous facies types are restricted to the high-energy shoal facies.
b) Cyclicity: Volume and dimensions of the reservoir bodies seem to be mainly controlled by a hierarchy of stratigraphic cycles.
c) Paleorelief: Subtle paleo-highs are important for the spatial distribution of reservoir facies.
In this particular epeiric setting it proved most useful to use a deterministic facies modeling approach, while for the petrophysical modeling several algorithms conditioned to facies and cyclicity provided reasonable results.
Subsequently, the model was upscaled for flow-simulation, with Frontsim using various scenarios. The flow-simulations demonstrated the need for high resolution simulation grids in thin-bedded epeiric carbonate reservoirs.
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