Three-Dimensional Image-Based Reservoir Pore Space Reconstruction: Spatial Resolution, Field of View and Heterogeneity

A suitable choice of spatial resolution is essential to the three-dimensional (3D) image-based reconstruction of reservoir pore space: a too low spatial resolution may result in the omission of sub-resolution porosity while too high spatial resolution may lead to a field of view smaller than the representative volume. In this work, the 3D pore spaces of conventional and tight sandstone specimens are reconstructed by X-ray computed tomography with various spatial resolutions and equal edge voxel quantities to study the influence of spatial resolution on the reconstruction quality. Petrophysical properties such as porosities, permeabilities and pore (throat) structure parameters are calculated from the 3D images and measured by helium porosity, Klinkenberg-corrected permeability and mercury intrusion capillary pressure porosimetry for comparison. High-resolution images are sampled from different positions in the specimens to evaluate the core-scale heterogeneities. The results show that 3D images with any single spatial resolution have limited detectivities on the pore and throat distribution of the reservoirs. If the edge voxel quantity is fixed, most of the image-derived petrophysical properties and their standard deviations change uniformly with the spatial resolution increment.