4.4. Effect of concentration ratio
The concentration ratio between high-solute fluid and lowsolute fluid determines the chemical potential gradient of different
concentration between the water in the natural fracture and the
water in the matrix. The higher the concentration ratio is, the
greater the osmotic pressure is. The effects of concentration ratio
on increasing oil recovery from rocks of 30.6 mD were investigated
at various temperatures with semi-permeable membrane formed
by 0.60 mol/L membrane-forming material as shown Fig. 7. The
higher oil recovery rate corresponds to higher concentration ratio
at various rock temperatures.