A new and improved material balance method by which the original dry gas in place and the original condensate in place can be calculated for a retrograde gas condensate reservoir has been formulated.

This new MBE is a result of theoretical research that is validated using experimental data. Ultimate validation of the new MBE can be made with field cases, and after a laboratory Bc procedure is established.

The new MBE requires a modified PVT procedure to determine the condensate formation volume factor, Bc as introduced here. This variable is currently not in use in the industry and hence is not being measured in current PVT lab procedures.

A basic assumption in the new MBE is that no reservoir condensate is produced. Additionally, the new MBE assumes normal pressure, volumetric conditions, and existence of the reservoir at the dew point. Modifications to accommodate water influx and rock and water compressibility were made to the basic equations after validation.

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