An approach to the calculation of hydrocarbon output of condensate gas cap reservoirs.

There are some large quantitative condensate gas cap reservoirs (gas condensate reservoirs with oil ring) in Dagang oil field. In the process of depletion recovery, gas breakthrough and oil breakthrough will exist, as a result of the unbalanced pressure fall between gas cap and oil areas. Accordingly, the hydrocarbon from producing well is likely to involve the mixture of crude oil, oil condensate and gas cap gas as well as solution gas. The authors put forward the two calculable methods of hydrocarbon output for condensate gas cap reservoirs, through the special thermodynamic property of condensate gas, combined with the method of reservoir performance analysis. The concrete instances show that 4 kinds of hydrocarbon output can be calculated accurately with the two methods. This will play a very important role for guiding the analysis of production performance, the research of remaining oil gas distribution, the development adjustment, determination of ultimate oil gas recovery factors as well as recoverable reserves of the condensate gas reservoirs.