Toward Better Understanding of the Ferrofluid Impregnation Process and Potential Artefacts—A Prerequisite for Reliable Interpretation of Magnetic Pore Fabrics

Magnetic pore fabrics (MPFs) serve as efficient proxy for alignment and preferential flow directions. Anisotropy of magnetic susceptibility impregnated samples reflects the shape arrangement ferrofluid-filled pores. Reliable interpretation requires that entire connected space is reached by ferrofluid. This study investigates impregnation efficiencies various methods (standard vacuum, pressure injection, flowthrough, resin impregnation) ferrofluids (water-based versus oil-based) on sandstone calcarenite with different wettabilities. Mass-based susceptibility-based further evaluate influence time rate. Because directional may introduce artificial fabrics, mutually perpendicular cores were measured, subsamples served to capture spatial variability. Impregnation vary between <1% >100%, injection using oil-based being least efficient. Oil-based ferrofluid generally leads lower compared mass-based efficiencies, suggesting particle filtering. Water-based show larger ranges efficiencies. In particular, >100% exclusively occur water-based ferrofluid, either standard vacuum or methods. MPFs after flowthrough reflect direction rather than fabric. A major challenge apply enough force reach sufficiently high without creating do not represent fabrics. While we cannot define a best practice yet, this improves our understanding process, provides experimental procedures identify artifacts.