Relative permeability regulation mechanisms of nano-microemulsion in tight oil and gas reservoirs

Key words:  nano-SiO₂  O/W nano-emulsion  structural characterization  relative permeability  adjustment mechanism

Abstract:

Application of relative permeability modifiers in tight oil reservoirs can effectively mobilize oil in rock matrix and improve the flow behavior of oil and water. Nano-fluid can be used to improve the oil and water relative permeability due to its large surface area, volume, quantum size effect. In this paper, nano-scale relative permeability modifiers formulated with diesel oil and dispersed nano-SiO₂ particles were prepared, and their structure and properties were characterized and evaluated. The experimental results show that the nano-scale percolation agent can be stable for 3 months, which is of an O/W type nano-microemulsion with a particle size of 4.351 nm. The median particle size of different mass fraction relative permeability modifiers ranges from 3 to 7 nm. The interfacial tension of oil and water is between 0.5-5 mN/m, and the average contact angle on carbonate rock tablets is between 40° and 75°. SEM testing shows that the rock surface treated by the nano-scale relative permeability modifiers became uniform and smooth, and it can be coated by nano-adsorbent films. The decrease of oil relative permeability in carbonate core is below 20％, but the decrease of water relative permeability is over 60％ after the treatment by the nano-scale relative permeability modifiers.