Methods and systems for predicting oil production from a reservoir are configured for obtaining production data from a hydrocarbon reservoir, the production data comprising data representing a fractional oil flow; determining, based on the production data, a relationship between the fractional oil flow and cumulative liquid production; identifying, based on the relationship between the fractional oil flow and cumulative liquid production, a post-water breakthrough point; estimating a value for a group parameter at a reference point of the relationship occurring after the post-water breakthrough point; and based on the value of the group parameter, generating a prediction of a future fractional oil flow and a future rate of production of oil from the hydrocarbon reservoir.