Analysis of heterogeneity and permeability anisotropy in carbonate rock samples using digital rock physics

In this study, we processed and used images of five carbonate rock samples obtained from three-dimensional (3D) computed tomography (CT) scans to calculate porosity and directional permeability. Subsamples taken at three positions along each original core plug image were processed to segmented images using image processing methods. Porosities were calculated by the voxel statistics method based on a segmented image. Absolute permeabilities of these subsamples in the three main perpendicular directions (one axial, z, and two transverse, x and y) were calculated by applying the parallel lattice Boltzmann method (PLBM) in our high-performance computing cluster (HPCC). The heterogeneity and permeability anisotropy were analyzed by combining the experimental results, the rock images, and simulated results, which included visualization of the velocity field and calculated parameter values. By analyzing these data, we found that these carbonate rock samples had strong heterogeneity and clear permeability anisotropy. In addition, we also found a close relationship between the measured values of the whole core samples and the maximum (minimum) values of the simulations for porosity (permeability). We verified that the characteristics of pore geometry, flow velocity distribution, and transport properties can be captured using DRP.