In threedimensional modeling, the viscous oil dis� placement efficiencies of working substances are tradi� tionally considered as constants for the lithotypes dis� tinguished. The experimental works of studying the displacement of viscous oils by different working agents on long reservoir models demonstrate that the working substance depends on the volume of pump� ing. This circumstance has allowed us to justify the possibility of oil recovery increase in developed oil deposits. The effectiveness of the development of oil deposits is determined by the oil recovery factor (ORF). In the 1950s Academician A.P. Krylov proposed the follow� ing simple formula for calculating the ORF: