Experimental Studies of Unstable Displacement in Carbonate and Sandstone Material

摘要

This paper is an experimental study of unstable miscible displacement in porous media, focused on viscous fingering instability. Experimental study of viscous unstable miscible displacements, have been made in 2D slabs of Bentheimer sandstone and vuggy carbonate. The sandstone represents a relatively homogeneous porous medium, while the vuggy carbonate is more heterogeneous. The frontal instability is visualized using a 2D X-Ray scanner. The objectives of this study were to improve description of viscous fingering and attempt to clarity the mechanisms of finger growth in sandstone and carbonates. The development of the fingers was drastically different in sandstone and vuggy carbonate. Multiple thin sharpened fingers emerge and propagate in the sandstone material. The unstable displacement in vuggy carbonate shows a much smaller number of fingers which are more diffuse and not as clearly defined as in sandstone. Finger growth mechanisms are discussed and effect of flow rate and variation in injection area is also included. Also immiscible displacement and effect of change in wettability on fingering of water displacing oil at adverse mobility ratio was studied. At water wet condition capillary smears the fingers even at high viscosity ratio. Changes in wettability dampen the capillarity and fingers then become more pronounced.