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Pore pressure prediction in shales is typically addressed using 1D compaction methods. However, this approach is only valid in basins where disequilibrium compaction is the dominant overpressure generation mechanism. For basins subjected to tectonic deformation, the predictions made by 1D methods are likely to be deficient due to the impact of lateral stresses on compaction and overpressure generation.
In this research, we use a coupled fluid flow-geomechanical approach that accounts for the full 3D stress tensor to model the mechanical compaction of mudstones where tectonic regimes are significant. We use a 2D plain strain column to investigate the effect of different factors of basin burial and tectonic histories on stress, porosity and overpressure.
From the different cases analysed the models predicted an increase in overpressure of up to 16 MPa at 3.5 km dept and a porosity loss of up to 6 porosity units due to the tectonic deformation.