A New Image Upscaling Method for Digital Rock Simulation of Conglomerate Reservoir

The low permeability conglomerate rock has a strong heterogeneity with a wide range of pore radius from submillimeter to nanometer. The traditional digital rock technology is based on micro-CT image with a resolution up to 0.5 µm, which leads to a lower porosity and higher permeability than the laboratory measurements. This paper proposed a new image upscaling method to capture the heterogeneity, and the conglomerate rock in the southern margin of Junggar, Xinjiang Oilfield, was used for validation. The micro-CT scan of the core plug was carried out to obtain the submillimeter porosity (with a resolution of 10-20 μm), and subsamples with a physical size of 1-3 mm3 were taken to obtain the micro-porosity (with a resolution of 1-2 μm). Then a small amount of samples was analyzed with a magnification of 500×, 5000× using scanning electron microscope (SEM) to obtain the nano-porosity image (with a resolution of 20-200 nm). The features of four-scale porosities are integrated to obtain the total porosity of the core plug, and the Brinkman method is used to calculate the permeability based on the multi-scale model. The results obtained by the image upscale method match the experimental data very well, which improves the digital rock technology for the industry practice.