Mechanically Robust 3D-Printed Proxies for Permeability Measurement of Burrowed Strata

Abstract Quantifying and accurately measuring bulk permeability in bioturbated strata remains a significant challenge, primarily due to the difficulty of obtaining representative samples that adequately capture connected networks controlling fluid flow. These representative volumes often exceed the laboratory-scale testing. Previously, permeability assessments for such large samples have relied on numerical simulations, where direct permeability measurements for these large burrowed strata remain challenging. However, recent advancements in computed tomography (CT) imaging and 3D printing technologies have enabled high-resolution reconstruction of burrow networks, which can then be scaled down to laboratory-compatible sizes. Despite this progress, issues persist, particularly with 3D-printed replicas produced via fused deposition modeling (FDM). These models frequently fail under the confining pressures applied during permeability testing due to structural deficiencies and fluid leakage. After the failure of ten FDM-printed replicas, this study identifies critical parameters for achieving mechanically robust replicas. Specifically, Polyethylene Terephthalate Glycol) PETG (filament demonstrated markedly superior load-bearing capacity and pressure tolerance compared to Polylactic Acid PLA, significantly minimizing sample failure. Furthermore, the use of 100% matrix infill was found to be crucial for maintaining structural integrity, despite the longer print times required. Finally, applying an epoxy surface coating effectively sealed inter-layer voids inherent to FDM fabrication, thereby preventing fluid leakage and enhancing mechanical integrity for the printed replica. The successful printing of pressure-tolerant 3D replicas represents a major advancement in experimentally measuring the permeability of bioturbated strata. This breakthrough paves the way for a better understanding of bulk permeability within the burrowed strata.