Abstract
Over the last 3 decades, Digital Rock Physics (DRP) has become a complementary part of the characterization of reservoir rocks due to the non-destructive testing character of this technique. The use of high-resolution X-ray Computed Tomography (XRCT) has become widely accepted to create a digital twin of the material under investigation. Compared to other imaging techniques, XRCT technology allows a location-dependent resolution of the individual material particles in volume. However, there are still challenges in assigning physical properties to a particular voxel within the digital twin, due to standard histogram analysis or sub-resolution features in the rock. For this reason, high-resolution image-based data from XRCT, transmitted-light microscope, Scanning Electron Microscope (SEM) as well as geological input properties like geological diagenesis, mineralogical composition, sample’s microfabrics, and estimated sample’s porosity are combined to obtain an optimal spatial segmented image of the studied Ruhr sandstone. Based on a homogeneity test, which corresponds to the evaluation of the gray-scale image histogram, the preferred scan sample sizes in terms of permeability, thermal, and effective elastic rock properties are determined. In addition, these numerically derived property predictions are compared with laboratory measurements to obtain possible upper limits for sample size, segmentation accuracy, and a geometrically calibrated digital twin of the Ruhr sandstone. The comparison corresponding gray-scale image histograms as a function of sample sizes with the corresponding advanced numerical simulations provides a unique workflow for reservoir characterization of the Ruhr sandstone.
Highlights
Digital Rock Physics (DRP) and its use of non-destructive methods to determine permeability or effective elastic rock properties have become a complementary part in reservoir characterization over the past 3 decades (e.g., Blunt and King, 1991; Iassonov et al, 2009; Andrä et al, 2013a; Andrä et al, 2013b)
The raw X-ray Computed Tomography (XRCT) data set must be technically evaluated based on the gray-scale histogram, existing X-ray artifacts, and the agreement with a REV
The manipulation of the assigned phases is contrasted with four geological verification steps, which are intended to ensure a meaningful result during the segmentation process (Figure 4)
Summary
Digital Rock Physics (DRP) and its use of non-destructive methods to determine permeability or effective elastic rock properties have become a complementary part in reservoir characterization over the past 3 decades (e.g., Blunt and King, 1991; Iassonov et al, 2009; Andrä et al, 2013a; Andrä et al, 2013b). 2013; Araújo, 2014) and to achieve the climate targets that have been set (e.g., Rogelj et al, 2016), currently non-fossil reservoirs are studied, such as in geothermal energy projects (e.g., Fridleifsson et al, 2008; Goldstein et al, 2011). For this purpose, the determination of the thermal conductivity, as well as the heat capacity, is becoming increasingly important in DRP. DRP will be used to further investigate the specific rock properties of the Ruhr sandstone, which so far can only be answered with great effort using classical laboratory methods One of the essential questions to be answered in the coming years is: Which geological horizons are suitable for geothermal projects? DRP will be used to further investigate the specific rock properties of the Ruhr sandstone, which so far can only be answered with great effort using classical laboratory methods
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