Rock properties evaluation for carbonate reservoir characterization with multi-scale digital rock images

Digital rock analysis (DRA) following the digital imaging techniques can be used to image detailed rock microstructures and simulate rock properties, such as porosity and permeability, for reservoir characterization. However, for most carbonate rocks, there are apparent differences in rock texture and minerals and clear variations of rock properties with location. This kind of heterogeneity often leads to a degree of unpredictability in DRA simulation. In addition, smaller sample size is necessary for a higher resolution image but the rock properties derived from bigger physical sample are more representative. Therefore, for a heterogeneous rock sample, it is impractical to predict its rock properties with only single resolution image. In this paper, we evaluate the rock properties using two heterogeneous carbonate rock samples and their corresponding multi-scale digital rock images including thin sections, scanning electron microscope (SEM) and X-ray computed tomography (XCT) images. A DRA upscaling method is also proposed. The analysis and results show that: 1) the simulated porosity and permeability agree well with their lab measurements; 2) the heterogeneity is clearly observed with these 2D and 3D rock images and their corresponding simulations; 3) the rock properties of the two carbonate rock samples are well evaluated by these rock images, lab measurements and numerical simulations.