POELCHAU, HARALD S., Institute of Chemistry and Dynamics of the Geosphere 4, Julich, Germany

ABSTRACT: Modeling an Exhumed Basin: A Method for Estimating Eroded Overburden

The Alberta Deep basin in western Canada has undergone a large amount of erosion after deep burial in the Eocene. Basin modeling and simulation of burial and temperature history require estimates of maximum overburden for each gridpoint in the basin.

Erosion generally is estimated with shale compaction trends. For instance, the commonly used Magara technique attempts to establish a sonic log gradient for shales and uses the intercept with uncompacted shale values as a first indication of overcompaction and amount of erosion. Since such gradients are difficult to establish in many wells, an extension of this method was devised to help map erosion over a large area. Sonic values of shales are calibrated with compaction gradients to give an equation for amount of total restored overburden for the same formation in several wells. This equation then can be used to estimate and map total restored overburden for all wells in which this formation has been logged.

The example from the Alberta Deep basin shows that trend and magnitudes of erosion or overburden agree with independent estimates using vitrinite maturity values.

AAPG Search and Discovery Article #90990©1993 AAPG International Conference and Exhibition, The Hague, Netherlands, October 17-20, 1993.