THE REAL RESERVOIR ROCK GEOBIOCELL: A NOVEL MICROFLUIDIC FLOWCELL FOR REAL-TIME IN-VITRO TRACKING OF SUBSURFACE MICROBE-WATER-ROCK INTERACTIONS

In this study, we developed a novel microfluidic experimental test bed, herein called the Reservoir Rock GeoBioCell (RRGBC), in which a thick section of actual subsurface reservoir core is mounted within a microfluidic flowcell. This RRGBC provide platform to overcome inherent limitations of the traditional microfluidic devices (i.e. micromodels) to represent the properties of actual subsurface environment, i.e., heterogeneous pore geometries and bio-geochemically reactive surfaces.

Siliciclastic sandstones core samples were impregnated with Super Glue^® adhesive and attached to glass slides. Custom petrographic rock sections (~0.5 mm thick) were prepared and acetone was then used to remove the Super Glue^® from. A microfluidic PDMS channel was molded to hold the thin section with one port embedded at each end of the channel for inlet & outlet. The separated thick section was plasma bonded to PDMS channel from the top-side and another PDMS coated cover glass from bottom-side to form a close channel passing through the thick section pore matrix. Finally, the entire assembly was put into an aluminum manifold to provide extra support against pressure inside the GBC.

The pore geometries and minerals reactivity were characterized using reflected, transmitted, fluorescence, and Cathodoluminescence microscopy on the thick section of the actual rock outside and/or inside the GBC, and were subsequently verified by Raman Spectroscopy in in-situ conditions inside the GBC. A GBC tracer test was conducted, and micro-flow paths and solute breakthrough within the thick section were characterized using fluorescence multi-photon confocal microscopy. A multiphase flow experiment was performed and displacement of fluorophore loaded aqueous medium with light oil was tracked using fluorescence microscopy. Activity of an oil-degrading mix culture was monitored using alamar Blue^® cell viability assay dye. The RRGBC developed in this study is useful for quantitatively testing and monitoring the physical, chemical and biological factors that affect subsurface carbonate diagenesis and other biogeochemical reactions. It is a powerful experimental tool for studying issues related to the oil and gas industry, geological carbon sequestration, and groundwater remediation.