Upscaling of Plastic Geomechanical Properties to Reproduce Anisotropic Failure in Heterogeneous Continua

The importance of geomechanical simulation is well documented for projects associated with significant pressure and temperature changes. Deformations and failure zones in reservoirs will impact fluid flow, caprock integrity, and well integrity. However, geological modelling cell sizes are typically at the centimetre scale in order to incorporate geological features resulting in models with millions of cells which are computationally expensive for current reservoir-geomechanical simulations. One option to overcome these computational challenges is to properly upscale geomechanical properties and simulate at a larger scale with fewer gridblocks. While many current upscaling techniques normally assume failure criteria for each upscaled cell, anisotropic failure response caused by sub-grid heterogeneity are significant complicating factors for heterogeneous continua. A local numerical upscaling technique is proposed to obtain the anisotropic failure criteria for heterogeneous continua. The implemetation of it in a highly heterogeneous IHS system shows a large difference in M-C failure envelopes in different directions caused by different failure modes. With the optimum loading rate selected for the local triaxial tests based on a sensitivity analysis, the proposed techinique can be efficiently applied in large-scale models and determine anisotropic strength parameters which can reproduce the change of shear strength at different stress state.