--> Abstract: Quantification of Uncertainty in Reservoir-Scale Extensional Fault-Propagation Folds, Part 1: Finite Element Modeling Results, by Kevin J. Smart, Luc Huyse, Alan P. Morris, David A. Ferrill, David S. Riha, and Christopher J. Waldhart; #90078 (2008)

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Quantification of Uncertainty in Reservoir-Scale Extensional Fault-Propagation Folds, Part 1: Finite Element Modeling Results

Kevin J. Smart1, Luc Huyse2, Alan P. Morris1, David A. Ferrill1, David S. Riha2, and Christopher J. Waldhart2
1Department of Earth, Material, and Planetary Sciences, Geosciences and Engineering Division, Southwest Research Institute, San Antonio, TX
2Mechanical and Materials Engineering Division, Southwest Research Institute, San Antonio, TX

Field data from the Big Brushy Canyon monocline are combined with finite element and probabilistic modeling to bridge the gap between kinematic and mechanical analyses and provide quantifiable measures of uncertainty for a reservoir-scale extensional fault-propagation fold. The monocline is developed in Cretaceous Buda Limestone above tectonically thinned Del Rio Clay. The underlying Santa Elena Limestone is offset along a steep normal fault, but displacement is not transferred to the Buda Limestone because of thinning in the intervening Del Rio Clay. Deformation within competent Buda Limestone beds is concentrated in the monocline limb, and includes bed-perpendicular veins and bedding slip surfaces. Finite element models were constructed to reproduce the geometry and deformation distribution and to assess the impact of material properties and boundary conditions on structural evolution. The initial configuration replicated the assumed original layer thicknesses and geometry. Santa Elena and Buda Limestones are simulated with an elastic-plastic material. This material could not capture the observed thinning in the Del Rio Clay, so a visco-elastic material was selected for this interval. Frictional sliding surfaces allow for bedding-parallel slip. A displacement boundary condition was applied to the Santa Elena footwall to simulate faulting. Changes in strain with time were tracked so that bed-parallel extension and shear strain could be compared to field observations. Iterative finite element runs revealed the importance of benchmarking the results against the field geometry and strain distribution to provide a better understanding of the effects of material behavior and boundary conditions. Model outputs were compared with field observations to assess the accuracy of the numerical simulations in reproducing the characteristics of the natural prototype.

 

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas