The Oseberg oil field is produced by immiscible gas injection. Produced gas is reinjected, and the pressure is kept almost constant by additional injection of gas imported from the nearby giant Troll gas field. The so called TOGI scheme is described in another paper presented at this conference [1]. Fig. l gives a schematic representation of the field development.

By installing a Dew Point Control module (DPC) there is a potential for increased condensate production, which again leads to injection of a leaner processed gas (higher methane content). The question is if this early gain in liquid production could be offset by a reduction at a later stage.

As the lean injected gas mixes with the gas cap gas the liquid content of the gas decreases. When the injected gas contacts the oil component exchanges between the oil and the gas phase take place. In addition, compositional variation will occur during periods of pressure depletion. Such effects are demonstrated in a series of PVT experiments, reported in a previous paper [2].

Another important issue is the quantification of the total condensate (oil from gas) production, which in this case will add significant reserves to the previously estimated oil production.

In this work we explain how a multidisciplinary approach, combing process simulation, Equation of state PVT simulation, compositional and black oil reservoir simulation; leads to quantitative estimates of compositional effects.

The emphasis is on method rather than on quantitative results. We discuss the simulation tools that have been applied, how the required input data are generated, and how the component exchanges in the reservoir and various simulation artifacts may affect the results.

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