Hydromechanical Modeling of Stress, Pore Pressure, and Porosity Evolution in Fold‐and‐Thrust Belt Systems

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.

Predictability and controlling factors of overpressure in the North Alpine Foreland Basin, SE Germany: An interdisciplinary post-drill analysis of the Geretsried GEN-1 Deep Geothermal Well

“…resolved, yet. The study area is only a few kilometers away from the rst thrust front of the Eastern Alps and might therefore be in uenced by increased lateral stresses, which would in uence velocity-based and basin modelling-based pore pressure estimates (Gao et al 2018;Obradors-Prats et al 2017, 2016. Also, lateral pressure transfer (Lupa et al 2002;Yardley and Swarbrick 2000) could be a mechanism yielding either additional overpressure or even pressure regressions.…”

Predictability and controlling factors of overpressure in the North Alpine Foreland Basin, SE Germany: An interdisciplinary post-drill analysis of the Geretsried GEN-1 Deep Geothermal Well

“…Moreover, the role of lateral stresses is not resolved, yet. The study area is only a few kilometers away from the rst thrust front of the Eastern Alps and might therefore be in uenced by increased lateral stresses, which would in uence velocity-based and basin modelling-based pore pressure estimates (Gao et al 2018;Obradors-Prats et al 2017, 2016. Also, lateral pressure transfer (Lupa et al 2002; Yardley and Swarbrick 2000) could be a mechanism yielding either additional overpressure or even pressure regressions.…”

A Diagenesis Model for Geomechanical Simulations: Formulation and Implications for Pore Pressure and Development of Geological Structures

“…Here we adopt the so‐called Soft Rock 4 (SR4) critical state model, and the most relevant aspects of the critical state constitutive model for this paper will be summarized. For more details on the formulation of SR4 the reader is referred to Obradors‐Prats et al (, , ).…”