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Entering the two phase envelope can result in precipitation of hydrocarbon liquids (condensate dropout). Condensate dropout can result in abrupt decreases in productivity (near wellbore effect) and loss of ultimate recovery (reservoir effect). The productivity effect is more of a concern in low permeability (<50 md) reservoirs. To mitigate the potential of condensate dropping out in the reservoir which results in lower recovery, gas recycling is often considered to maintain the pressure above the phase envelope.
In one review of an offshore giant gas field, Epic used a compositional model with velocity dependent relative permeabilities to more accurately model the potential impacts. It became apparent that the high productivity of the field compensated for potential dropout effects and that in the short term, the real issue was the turbulent velocity skin effect.
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Key effects in gas condensates
Relative permeability enhanced as capillary number increases
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