A reservoir alteration process that affects crude oils that have been charged by dry gas within the reservoir. The gas equilibrates with the light components of the reservoir oil and escapes or migrates upward (usually through faulting) to a shallower reservoir carrying with it condensate dissolved from the parent oil, which remains behind. Both parent and daughter products show certain effects from this process: the parent hydrocarbons are now heavier in composition and enriched in light aromatics and cycloalkanes (e.g., toluene and methylcyclohexane) due to the loss of the lighter and more volatile fluids preferentially by volatility and fugacity differences. The condensate daughter product is of higher API gravity and is enriched in saturates.