Gas Correlations
Subtopics:
Ovalle et al.'s Correlation for Rv
Vaporized Oil Ratio (Rv)
In the "Black Oil" models, the gas component can exist either as free gas or as dissolved gas in the oil phase. The transportation of gas component between oil and gas phases is controlled by pressure and temperature. The functionality of this transportation is defined by solution gas ratio "Rs".
In the modified black oil (MBO) systems, in addition to the above behaviour, oil can condense out of the gas phase. This process is dominated by pressure and temperature and its functionality is defined by Vaporized Oil Ratio "Rv" (i.e., Hydrocarbon Liquid content of the gas). Strictly speaking, Rv is the ratio of barrels of produced stock tank oil per one MMscf of produced separator gas. For gas condensate and volatile oil system, we need to consider the liquid content in the gas phase.
Ovalle et al.'s Correlation for Rv
Ovalle et al.'s correlation is based solely on commonly available field data. Required field data is as follows: initial producing gas / condensate ratio from the first separator, initial stock tank liquid gravity in oAPI, specific gravity of initial reservoir gas, and reservoir temperature. This correlation does not need require the Dew Point pressure to calculate the "Rv" curve vs. pressure.
| n | Varn |
COn | C1n | C2n | C3n | C4n |
|---|---|---|---|---|---|---|
| 1 | In P, psi | 20.809 | -6.7095 | 0.5136 | 0 | 0 |
| 2 | APId | 11.175 | -1.2965 | 0.042311 | -0.0005438 | 2.49E-06 |
| 3 |
|
-13.365 | 27.652 | -18.598 | 4.3658 | 0 |
| 4 | TR,°F | -1.5309 | 0.0058453 | 1.40E-06 | 0 | 0 |
| APId | Gravity of stock-tank liquid, oAPI, determined when P ≥ Pd |
| P | Pressure, psi |
|
Reservoir gas specific gravity at P≥Pd (This value is the recombined gas specific gravity |
| TR | Reservoir temperature, °F |
| RV | Vaporized oil ratio, Stb/MMscf |