Calculation of P-Wave Velocity in Sandstones with Different Pore Size Distributions Using Digital Rock Model without Segmentation

Abstract

Calculation of elastic wave velocity using digital rock models is a powerful method to understand physical properties of rocks. However, one difficulty of the approach is to construct a proper digital model due to the uncertainty by the segmentation process of X-ray CT image. Recently, the segmentation-less method has been proposed to avoid the uncertainty, and has shown to be useful in application to Berea sandstone. In this study, we assessed the method through the application to Shirahama sandstone in addition to Berea sandstone, and confirmed whether the method can be applied to other types of sandstones. We also applied and compared two different rock-physics models to obtain elastic properties of a digital rock model. Our results showed that the segmentation-less method can be successfully applied to Shirahama sandstone as well as Berea sandstone. However, when the pore diameter of rock sample is smaller than the spatial resolution of CT image, we found that a correction is required when mapping the CT number to a density. Our results would be useful when applying the segmentation-less method to other types of sandstones.