using p/z approach for gas-condensate reservoirs

[catapam]

I posted here this text showed today by a colleague
It is said that for P?Z approach in a gas-condensate field you need to include the condensate as gas equivalent.
But in order to report GIIP that is in surface conditions you need to remove the condensate.
How are you doing this is unclear:

1. How are you calculating gas equivalent from condensate?
2. How do you know how much gas equivalent from condensate is in your final GIIP?
3. How are you coming with GIIP that is surface conditions (without condensate).

Retrograde-condensate reservoirs

Depletion behavior of retrograde-condensate reservoirs can be handled through the p/z analyses discussed previously* with the caveat that the z factor must be the two-phase z factor (see Natural gas properties). Two-phase z factors either may be obtained from laboratory tests or predicted from composition with an EOS. In wet-gas and retrograde-condensate reservoirs* cumulative gas produced must include both gas and liquid (as equivalent gas) production. This is particularly important for high-liquid-yield gases.

[DAH7542]

Hi Catapan if you have a PVT study done for a fluid sample you will find the answers to all of your questions there. In first place let's assume that the gas condensate reservoir is at an initial pressure greater that the dew point pressure over the entire extent of the hydrocarbon column so that there is only a gas phase in the reservoir. That volume can be measured or volumetrically estimated as let's say 1.0 million SCF of gas condensate (reservoir fluid). Note that here this volume contains all hydrocarbons that ultimately would be produced as gas or condensate in the surface so the OGIP contains everything. However from a PVT study you can know for sure how many barrels of condensate would be produced at the stock tank out of that volume if you could take all the OGIP to the surface. Not only that you can know for sure how many cubic feet of gas (gas phase produced in the surface) you would produce at the primary separator and secondary separator if you could also take all the OGIP to the surface. So from the PVT study (in Corelab's reports see section "Calculated Cumulative Recovery During Depletion") you can break down your OGIP into volumes that would be produced as gas in the surface and as condensate at the surface. The same section in the PVT study will tell you the same thing for all other pressures below the dew point pressure. I decided to attached that section from a PVT study I got so that you can see it for your self.