Many gas-condensate systems exist as a single-phase liquid in the reservoir. Condensation generally takes place at the separator, in the wellbore, or in the reservoir very near the wellbore. When modeling gas condensate systems at reservoir conditions, gas and condensate rates measured at surface conditions are combined into a single-phase rich gas using recombination.
The recombination calculation takes the volume of condensate, vaporizes it, and adds it to the gas volume to obtain a single-phase rich gas as it exists in the reservoir. A recombined gas gravity is also calculated for use in analytical models.
Given the specific gravity of measured separator gas, the condensate gas ratio (CGR), and the specific gravity of the condensate, the recombined gas gravity can be calculated using the following equation:
Where:
The recombined gas rate is calculated using the following equation:
The recombined gas rate factor (RGRF) is defined as recombined gas rate divided by the measured gas rate:
