Image registration of 2D optical thin sections in a 3D porous medium: Application to a Berea sandstone digital rock image
This work addresses the challenge of integrating multimodal imaging for more accurate digital rock physics, though it is incremental as it applies existing optimization methods to a specific domain.
The study tackled the problem of aligning 2D optical thin-section images within a 3D digital rock volume to improve rock property computations, achieving a structural similarity index of 0.990 for Berea sandstone and revealing differences such as 50% more porosity and 25-30% lower elastic moduli compared to CT images.
This study proposes a systematic image registration approach to align 2D optical thin-section images within a 3D digital rock volume. Using template image matching with differential evolution optimization, we identify the most similar 2D plane in 3D. The method is validated on a synthetic porous medium, achieving exact registration, and applied to Berea sandstone, where it achieves a structural similarity index (SSIM) of 0.990. With the registered images, we explore upscaling properties based on paired multimodal images, focusing on pore characteristics and effective elastic moduli. The thin-section image reveals 50 % more porosity and submicron pores than the registered CT plane. In addition, bulk and shear moduli from thin sections are 25 % and 30 % lower, respectively, than those derived from CT images. Beyond numerical comparisons, thin sections provide additional geological insights, including cementation, mineral phases, and weathering effects, which are not clear in CT images. This study demonstrates the potential of multimodal image registration to improve computed rock properties in digital rock physics by integrating complementary imaging modalities.