Digital Rock Physics or Digital Rock is a rapidly advancing image-based technology for predicting subsurface properties of complex rocks (e.g., porosity, permeability, formation factor) to achieve more, cheaper, and faster results as compared to conventional laboratory measurements. We show that a combination of limited image resolution and a finite field of view, leads to the systematic underestimation of porosity and overestimation of permeability calculated using Digital Rock technology. We quantify these effects and derive the necessary corrections to estimate the true rock properties directly from the segmented micro-CT image. These novel solutions allow us to further mature DRP as a technology for existing and future fields.
Digital Rock Physics (DRP) aims to predict subsurface properties of complex rocks to achieve more, cheaper, and faster results as compared to conventional laboratory measurements (Fredrich et al., 1993; Keehm et al., 2001; Arns et al., 2005; Knackstedt et al., 2009). This is possible since DRP analyses can be carried out on a "as received" piece of rock (< 1 cm3) that can come from whole core, sidewall core, or a drill cutting, using state of-the-art micro-CT technology (Figure 1) and a combination of novel digital approaches (e.g., direct numerical simulation, deep learning, machine vision). However, for this technology to mature, it is important to demonstrate that it is feasible to estimate two of the most fundamental of all rock properties, porosity and permeability. Shell has recently performed a series of detailed studies to benchmark commercially available Digital Rock tools (Saxena et al., 2017) and vendors and arrived at the conclusion that there is no viable external commercial solution, as of 2018, that provides sufficiently accurate results in comparison to laboratory measurements. Raw image-derived properties typically underestimate porosity (by up to 6 p.u.) and overestimate permeability (by a factor of 10 or more) for reservoir rocks in Shell's portfolio. This is because the current pore-scale imaging is limited to image resolution of 1 - 2 microns and field of view of about 20003 - 40003 voxels.
