Many types of geofluids exist in the Earth's crust. Geofluids can occur as immiscible two-phase fluids, such as oil and brine or gas and brine. In this review, we present newly identified mechanisms of immiscible fluid flow based on recent advancements in X-ray and computer technologies. Historically, immiscible geofluids have been studied in association with resources such as groundwater, petroleum, and natural gas; however, the research field is also important from a scientific perspective. In recent years, CCS (carbon capture and storage) has been established as an effective tool for mitigating climate change caused by anthropogenic CO₂. This has led to experimental studies on the immiscible fluid flow of brine and supercritical CO₂ mixtures in porous rocks, in which wetting and non-wetting characteristics control the fluid flow. Water or brine are wetting fluids, and oil or gas (including supercritical gas) are non-wetting fluids in the case of most geologic solids. Wetting results in capillary pressure and controls the flow of immiscible fluids. Rock permeability has previously been considered a primary control on fluid flow; however, recent studies have reported phenomena in immiscible fluid flow (e.g., snap-off and viscous fingering) that cannot be explained by rock permeability alone.