Abstract: New Compaction Model for the Simulation of Sedimentary Basins

Frederic Schneider, J. L. Potdevin, I. Faille

This study completes a previous work in which the compaction model that is conventionally used in models such as Temispack, has been interpreted and formalized. The new model described here differs from the previous one by the introduction of a viscoplastic component in the formulation of the stress-strain relationships. The addition of this component, allows to take into account, at a macroscopical scale, viscous phenomena of compaction such as pressure solution.

A sensitivity analysis has been carried out with different values of extrapolated viscous coefficients. The viscous deformation is noteworthy (10% of the total strain) for basins older than 10 Ma when the viscous coefficient is lower than a critical value of 1.0 GPa.Ma.

With field data from literature, it is possible to estimate the elastoplastic and viscoplastic parameters which define a chalk rheology. Assuming that chalk which had no suffer diagenesis, has been compacted along an elastoplastic path, it is possible to calibrate easily the elastoplastic parameters. Such a calibration can be also performed with laboratory measurements. When chalk has suffered diagenesis, we assume that the present-day porosity versus effective-stress relationships, extracted from well logs, results both from elastoplastic deformation and viscoplastic deformation. With this assumption, chalk viscosity is evaluated around 2.5 GPa.Ma.

In conclusion, this model allows to take into account, in a realistic way, pressure solution phenomena which participate to sediments compaction, and, in spite of restrictive hypotheses, the model gives solutions which are physically acceptable.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994