Deformation, stress, and pore pressure in an evolving suprasalt basin

Abstract

AbstractWe develop a two‐dimensional plane strain large‐deformation coupled poroelastoplastic finite element model to simulate initiation and rise of a salt wall from a flat salt body during sedimentation. We run transient analyses with high‐permeability and low‐permeability sediments in the model to simulate drained conditions and overpressure (or pore fluid overpressure). We investigate deformation, stress, and overpressure in the evolving suprasalt basin. Model results show that horizontal stress increases even higher than vertical stress at the flank of the salt wall and in the minibasin due to horizontal pushing out of the rising salt wall and that orientations of principal stresses rotate in the minibasin relative to far‐field stress state. Model predicts that compared with far‐field overpressure, the overpressure near the salt wall and within the minibasin is largely perturbed by the salt body. We find that perturbations of pore pressure (or pore fluid pressure) near the salt wall and within the minibasin cannot be resolved by traditional pore pressure prediction methods such as normal compaction trend approach and mean stress model approach. In order to predict pore pressure more accurately, especially in the regions near salt bodies or where stresses are perturbed, we need to apply a method that includes both effects of mean effective stress and deviatoric stress on pore pressure and compaction, for example, the Modified Cam Clay model approach, to pore pressure prediction. Our results provide geoscientists insights into evolution of salt basins, near‐salt deformation, stress, overpressure, and overpressure prediction methods and have implications for near‐salt wellbore drilling programs.