USING RESIN-BASED 3D PRINTING TO BUILD GEOMETRICALLY ACCURATE PROXIES OF POROUS SEDIMENTARY ROCKS

3D printing is capable of transforming intricate digital models into tangible objects, allowing geoscientists to replicate the geometry of 3D pore networks of sedimentary rocks. We provide a refined methodology for manufacturing scalable porous models (“proxies”) using stereolithography 3D printing that can be used in repeated flow experiments (e.g., core flooding, permeametry, porosimetry). Typically, this workflow involves two steps, model design and 3D printing. In this study, we explore how the addition of post-processing and validation can reduce uncertainty in the 3D-printed proxy accuracy (i.e., the differences between digital and 3D-printed model). Post-processing involved a multi-step pressurized flushing with ethanol and oven drying. Proxies are validated by: 1) helium porosimetry, and 2) digital measurements of porosity from thin-section images of 3D-printed proxies. 3D printer resolution was determined by measuring the smallest open channel in 3D-printed “gap test” wafers. This resolution (400 µm) was insufficient to build porosity of Fontainebleau sandstone (~13%) from computed tomography data at the sample’s natural scale, so proxies were printed at 15-, 23-, and 30-fold magnifications to validate the workflow. Helium porosities of the 3D-printed proxies differed from digital calculations by up to seven percentage points. Results improved after pressurized flushing with ethanol; porosity difference reduced to ~one percentage point. Uncertainties remain regarding the nature of sub-micron “artifact” pores imparted by the 3D printing process. This study shows the benefits of including post-processing and validation in any workflow to produce porous rock proxies used to study reservoir rock properties.