Effect of X‐Ray Computed Tomography Imaging Parameters on Quantification of Petrophysical Properties

Abstract

Abstract Three‐dimensional (3D) X‐ray computed tomography (X‐ray CT) imaging has emerged as a nondestructive means of microstructural characterization. However, obtaining and processing high‐quality and high‐resolution images is time‐consuming and often requires high‐performance computing, particularly with a high number of projections. This work evaluates the effect of 3D X‐ray CT imaging parameters on pore connectivity and surface area quantification in sandstone samples of varied composition. Samples from Bentheimer and Torrey Buff formations are imaged via 3D X‐ray CT imaging at resolutions ranging from 1.25 to 15 μm, bin sizes 1, 2, and 4, and number of projections from 400 to 4,500. Collected images are processed and analyzed using ImageJ and MATLAB to discern petrophysical properties and the results are compared with each other and Mercury Intrusion Capillary Pressure (MICP) results. Overall, little variation in bulk porosity with changing scanning parameters is observed. However, for low resolution and projection numbers, connected porosity is lower compared to bulk porosity due to a failure to capture microfeatures. Overall, mineral surface area is observed to decrease with increasing bin size, voxel size, and projection numbers, except an observed increase with projection numbers for Torrey Buff. The Torrey Buff samples contains comparatively more clays and even the highest resolution (1.25 μm) fails to separate the micrograins, which is reflected in the pore size distribution. Identifying these variations are helpful as discrepancies in imaged pore connectivity and surface area can largely impact assessments of fluid flow and transport in reactive transport simulations informed by this data.

Keywords

• imaging
• X‐ray computed tomography
• surface area
• pore size distribution
• pore connectivity
• porosity