T23B-2944
Deformation, Stress, and Pore Fluid Pressure in an Evolving Supra-salt Basin: A Finite-element Modeling
Tuesday, 15 December 2015
Poster Hall (Moscone South)
Gang Luo1,2, Peter B Flemings3, Michael R Hudec2 and Maria A Nikolinakou2, (1)Key Laboratory of Computational Geodynamics, University of Chinese Academy of Sciences, Beijing, China, (2)Bureau of Economic Geology, Jackson School of Geosciences, The University of Texas at Austin, Austin, TX, United States, (3)Jackson School of Geosciences, The University of Texas at Austin, Austin, TX, United States
Abstract:
Many driving mechanisms have been proposed to explain rise of a salt structure and formation of a minibasin. However, these studies mainly focus on qualitative discussion and analog modeling on these mechanisms. Quantitative studies such as numerical modeling are much needed. In this study, we apply a commercial finite-element software package, ELFEN, to develop two-dimensional plane-strain large-deformation coupled poromechanical finite-element models. We simulate initiation and rise of a salt wall from a flat salt body driven by differential topographic loading during sedimentation processes. We run drained and transient analyses, and investigate deformation, stress and pore fluid overpressure in the evolving supra-salt basin. Our model results show that 1) 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; 2) orientations of principal stresses in the minibasin rotate relative to far-field stress field; 3) overpressure varies much through different vertical profiles across the minibasin: relative to far-field overpressure, the overpressure near the salt wall and within the minibasin is largely perturbed by the rising salt wall. Through comparing our finite-element model overpressure with that predicted by traditional pore pressure prediction methods such as normal compaction trend approach and mean stress model, we find that the perturbations of pore pressure near the salt wall and within the minibasin, can not be resolved by these traditional prediction methods. Hence we propose to develop and apply a general Modified Cam Clay soil model to predict pore pressure. These results in this study help geoscientists understand near-salt deformation, stress, and pore fluid overpressure, provide insights into near-salt overpressure prediction, and provide implications for near-salt wellbore drilling programs.
