We develop two-scale workflows to determine the geomechanical properties of shale and carbonate formations at the 1-cm scale based on its forming structure and minerals at the small scale (~ 10 nm – 1 micrometer). The workflow is based on a two-scale approach, which is hierarchical, and uses a finite element method (FEM). A workflow for predicting the anisotropic elastic properties of a shale is shown here.
The two-scale approach accounts for the void structure, the mineralogy, the grain size, and the microfabric structure of the solid phase in the matrix, all of which can be determined from small-scale measurements on drill cuttings. We first simulate the elastic deformation of a solid grain with a known mineralogy by accounting for the grain size and its elastic properties (small scale). We then develop a core-scale model based on the volume fractions of the minerals, which are obtained from X-ray diffraction (XRD), for different realizations of the spatial distribution of the solid grains (large scale).
We modify the workflow to capture different properties of a formation. The results for the elastic properties of a carbonate formation (published in RMRE) and New Albany, Rocky Mountain Siliceous, lower Bakken, and Barnett shales (published in SPERE) are promising. In a different study (unpublished), we predicted the anisotropic elastic moduli of the shale samples from Lower Bakken with less than a 7% difference from independent 1-cm scale measurements. We are currently modifying the workflow to simulate the time-dependent behavior.
Representative articles
- Sakhaee-Pour, A., and Li, W. (2019). Two-scale geomechanics of shale. SPE Reservoir Engineering & Evaluation, 22(01), 161 – 172.
- Li, W., and Sakhaee-Pour, A. (2018). Two-scale geomechanics of carbonates. Rock Mechanics and Rock Engineering, 51(12), 3667 – 3679.