Upscaling elastic geomechanical properties is important for reducing the computational requirements of geomechanical simulation while honoring local heterogeneities in rock properties. During simulation elastic properties are often considered homogeneous; however, there is increasing interest in understanding the effect of heterogeneity on geomechanical simulation. Upscaling allows for the generation of realistically sized numerical models that can be simulated in a reasonable timeframe and also account for small scale heterogeneities. A novel local numerical upscaling technique is proposed to describe the macroscopic elastic behavior of complex heterogeneous media. This technique is compared to conventional analytical techniques and is shown to produce superior results when assessing the upscaling error of a synthetic facies model. The geomechanical response, volumetric strain in this study, of the coarse upscaled models are compared to the geomechanical response of the fine scale models with the proposed numerical technique producing results most similar to the fine scale model.
The main objective of geomechanical simulation is to predict the deformation behavior of geo-materials when loads are applied. Rock mechanical properties, both elastic and plastic, are critical input parameters. Mechanical Earth Models (MEMs) are comprehensive geological models which include in-situ stress magnitudes/directions and also heterogeneous maps of rock mechanical properties. However, layer cake geomodels with constant elastic and plastic properties dominate the geomechanical field. Rather, heterogeneous MEM’s are proposed in order to account for known rock heterogeneity and better predict the geomechanical response of an area of interest. In addition to better predicting geomechanical response, the consideration of geostatistical techniques for generating static rock properties allows for the quantification of uncertainty through processing multiple realizations. The limiting factor in considering multiple realizations and fine scale heterogeneous property models is the CPU requirement of the geomechanical simulator (e.g. FLAC). This is the main motivation for considering upscaling.
