Hydromechanics of a virtual rock core

In this study, numerical tests of hydromechanics were conducted on a virtual rock core. A series of 2D digital images is captured through X-ray CT scanning of the rock sample. Each 2D CT image is then processed to ascribe a map of pixel values. The map of pixel values is thresholded to relate pore density that defines grain or pore to porosity. The same number of 2D CT images that represent the porosity distribution (map) are then used to construct the 3D virtual rock core. Through interpretations, the porosity for each voxel within the virtual rock core is defined. Through these steps, a 3D porosity map within the virtual rock core was created. Maps of other physical properties such as elastic modulus and permeability were produced through their empirical relations with the porosity. These property maps were used as direct inputs for the hydromechanical numerical tests. The numerical experiments are completed through the development and application of a porosity-based finite element hydro-mechanical model. In this hydromechanical model, the porosity changes with the volumetric strain and pore pressure. Because both elastic modulus and permeability are defined as a function of porosity, all these three important physical properties change with time. Results from these numerical tests demonstrate the impacts of rock heterogeneity on the hydromechanical performance (without considering the heterogeneity, the fluid flux could be overestimated by 130%). Through comparing the results from numerical experiments with those of the ideal homogeneous rocks, these heterogeneous impacts were quantified.