Hydromechanical Modeling of Stress, Pore Pressure, and Porosity Evolution in Fold‐and‐Thrust Belt Systems. Issue 11 (27th November 2017)

• Record Type: Journal Article
• Authors: Obradors‐Prats, J.; Rouainia, M.; Aplin, A. C.; Crook, A. J. L.
• Is Part Of: Journal of geophysical research. Volume 122:Issue 11(2017)
• Page Start: 9383
• Page End: 9403
• Publication Date: 2017-11-27
• Subjects: geomechanical modeling -- thrust and fold belts -- structural deformation -- overpressure and porosity -- tectonic compaction -- stress paths; Geomagnetism -- Periodicals; Geochemistry -- Periodicals; Geophysics -- Periodicals; Earth sciences -- Periodicals; 551.1
• DOI: 10.1002/2017JB014074
• Languages: English
• ISSNs: 2169-9313

Abstract

Abstract: We present coupled, critical state, geomechanical‐fluid flow simulations of the evolution of a fold‐and‐thrust belt in NW Borneo. Our modeling is the first to include the effects of both syntectonic sedimentation and transient pore pressure on the development of a fold‐and‐thrust belt. The present‐day structure predicted by the model contains the key first‐order structural features observed in the field in terms of thrust fault and anticline architectures. Stress predictions in the sediments show two compressive zones aligned with the shortening direction located at the thrust front and back limb. Between the compressive zones, near to the axial plane of the anticline, the modeled stress field represents an extensional regime. The predicted overpressure distribution is strongly influenced by tectonic compaction, with the maximum values located in the two laterally compressive regions. We compared the results at three notional well locations with their corresponding uniaxial strain models: the 2‐D thrust model predicted porosities which are as much as 7.5% lower at 2.5 km depth and overpressures which are up to 6.4 MPa higher at 3 km depth. These results show that one‐dimensional methods are not sufficient to model the evolution of pore pressure and porosity in contractional settings. Finally, we performed a drained simulation during which pore pressures were kept hydrostatic. The predicted geological structures differ substantially from those of the coupled simulation, with no thrust faulting. These results demonstrate that pore pressure is a key control on structural development. Key Points: Coupled forward geomechanical modeling of thrust and fold evolution including syntectonic sedimentation is developed Significance of overpressure in structural deformation style is shown Overpressure and porosity predicted by geomechanical models are more accurate than those estimated by 1‐D methods