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[WITHDRAWN] Multi-scale X-FEM faults simulations for reservois-geomechanical models

Faults are geological entities with thicknesses several orders of magnitude smaller than the grid blocks used to discretize reservoir and/or over-underburden geological formations. Introducing faults in a complex Reservoir and/or Geomechanical mesh therefore poses significant meshing difficulties. In our work, we introduce faults in the mesh without meshing them explicitly, by using the extended finite element method (X-FEM) in which the nodes whose support intersects the fault are enriched. For the Geomechanics, the fault is treated as an internal displacement discontinuity that allows slipping to occur using a Mohr-Coulomb type criterion. For the Reservoir, the fault is an internal fluid flow conduit that allows fluid flow in the fault as well as to enter/leave the fault. In the X-FEM, the framework of partition of unity is used to enrich the nodes. The faults are represented by enriching the displacement approximation with a discontinuous (Heaviside) function, whereas the approximation for the fluid pressure includes functions that admit a discontinuity in their normal derivative across the fault. The procedure has been implemented in 2D and 3D, for both structured and unstructured meshes. Examples that demonstrate the versatility and accuracy of the procedure(s) will be presented. Also, the influence of the rate of loading on activation of faults will be demonstrated.

Author(s):

N. Sukumar    
UC Davis
United States

Jean H. Prevost    
Princeton University
United States