Impact of Uplift/Erosion on Carbonate Petroleum Systems: An Analysis from Western Canada

P. H. Nadeau¹, J. Garland², S. Vasshus¹, G. Darke¹, and S. N. Ehrenberg^1
1 Statoil ASA, N-4035 Stavanger, Norway
² Cambridge Carbonates Ltd, Durham, DH1 4JR, United Kingdom

Geologic models for petroleum systems and exploration risks analysis have been applied to Upper Devonian carbonate plays, including Swan Hills, Leduc and Nisku accumulations of the Western Canada Basin. Public data bases for oil pools, including reservoir porosity and petroleum reserves have been combined with uplift/erosion models (Issler et al., 1999) and global data for carbonate reservoirs (Darke et al., 2004) to evaluate diagenetic controls on hydrocarbon migration and entrapment efficiency (Nadeau et al. 2005). The results for maximum burial depths versus maximum reservoir porosity agree well with published global data sets (Ehrenberg and Nadeau, 2005). Analysis of recoverable oil reserves versus maximum burial depth indicate that circa 75% of the recoverable reserves were entrapped between 2.5 and 4 km depth prior to Tertiary uplift and erosion. The impact of fill-spill migration can also be seen in the reserves distribution data, notably for the Redwater Field. Using thermal models for hydrocarbon migration and entrapment efficiency in carbonate hosted petroleum systems, the 2.5 and 4 km depths can be assigned to the 80 and 120°C isotherms respectively, at maximum burial. This interpretation allows reconstruction of the geothermal gradient of the Western Canada foreland basin at 27°C/km, corresponding to the thermal profile at the time of hydrocarbon charge for these carbonate plays.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005