Enhanced pore space analysis by use of <i>μ</i>-CT, MIP, NMR, and SIP

Abstract

Abstract. We investigate the pore space of rock samples with respect to different petrophysical parameters using various methods, which provide data on pore size distributions, including micro computed tomography (μ-CT), mercury intrusion porosimetry (MIP), nuclear magnetic resonance (NMR), and spectral-induced polarization (SIP). The resulting cumulative distributions of pore volume as a function of pore size are compared. Considering that the methods differ with regard to their limits of resolution, a multiple-length-scale characterization of the pore space is proposed, that is based on a combination of the results from all of these methods. The approach is demonstrated using samples of Bentheimer and Röttbacher sandstone. Additionally, we compare the potential of SIP to provide a pore size distribution with other commonly used methods (MIP, NMR). The limits of resolution of SIP depend on the usable frequency range (between 0.002 and 100 Hz). The methods with similar resolution show a similar behavior of the cumulative pore volume distribution in the overlapping pore size range. We assume that μ-CT and NMR provide the pore body size while MIP and SIP characterize the pore throat size. Our study shows that a good agreement between the pore radius distributions can only be achieved if the curves are adjusted considering the resolution and pore volume in the relevant range of pore radii. The MIP curve with the widest range in resolution should be used as reference.

Pore-scale visualization of hydrogen storage in a sandstone at subsurface pressure and temperature conditions: Trapping, dissolution and wettability

“…The dry sample was segmented into pores and grains which served as the mask for the wet segmented images. The porosity value of 22.8% obtained from the segmented volume is in good agreement with reported Bentheimer porosity values between 20 and 26% [57,58]. The image segmentation workflow for wet scans (with fluids) is detailed in Figure S3 (Supplementary Material), and the grayscale histograms for the raw and filtered images are shown in Figures S4 to S8 (Supplementary Material).…”

“…A water-wet Bentheimer sandstone (typical composition of Quartz: 91.7%, Feldspar: 4.86%, Clay: 2.68%, Pyrite and Iron Hydroxides: 0.17%) [56] sample with a diameter of 6 mm and a length of 27 mm was used as the porous medium. Bentheimer sandstone is a well-characterized texturally homogeneous rock, known to be water-wet with high porosity (20 to 26%) [56][57][58] and permeability (0.52 to 3.54 Darcy or 5:13 Â 10 À13 to 3:49 Â 10 À12 m 2 ) [56], making it a suitable candidate to initiate the first investigations for pore-scale H 2 -brinerock interactions at reservoir conditions that can be visualized using a micro-CT scanner. The sample's permeability to water was measured separately and found to be 2.9 Darcy…”