Retrograde phenomena – lithological body (bed, layer, stratum) capable of retaining fluids in reservoir and limiting a deposit in geological space. Fluid cutting-off properties depend on lithological profile and heterogeneity of the impermeable rock, on mineral composition of rock, void space structure, pressure differential in roof and bottom of impermeable seal, on capillary pressure of fluids, and on the impermeable rock thickness.

Many natural hydrocarbons multi-component systems have one retrograde area. For example, in formation fluids of gas condensate fields in most cases only retrograde condensation is observed. Retrograde phenomena are manifested in hydrocarbons multi-component systems of different compositions at different pressure and temperature values. It should be noted that pressure and temperature conditions resulting in retrograde phenomena in formation fluids of gas condensate and oil fields are often similar to pressure and temperature observed in field development practice. This causes fall-out of fluid components in gas-saturated reservoirs, changes in produced mix and in well productivity.