For Gas flooding calculation, OPGEE calculates using the same water flooding assumption WIR = 1 + WOR which can be better calculated given the following information and assumption.
The limitations in using the current equation for WOR and then WIR for CO2-EOR development.
Based on the historical CO2 floods, it has been shown that WOR > WIR.
Also, the above OPGEE default is meant for water flood as stated in the documentation, but even when gas flooding is set, the WOR and WIR are still calculated in the same way which underestimates WOR and WIR. The following equation is to be used to calculate WOR and WIR assuming for eg. WOR = 1.10 WIR (this needs to be studied further to quantify by how much water produced volumes are greater than injected volumes in specific for miscible CO2 floods) with the following assumptions:
Assuming CO2-EOR floods VRR =1 (Injected reservoir volumes = produced reservoir volumes)since the reservoir pressure is maintained and to be maintained > MMP for miscible floods.
Injected
GVF of CO2 from offsite for gas flooding (m3/std-m3) - Cell CD75
GVF of sour gas reinjection compressor (m3/std-m3)- Cell BY75
Volume weighted average GVF of gas = GVF of CO2 from offsite for gas flooding (m3/std-m3) ( 1- fraction of CO2 breaking through to pr %) + GVF of sour gas reinjection compressor (fraction of CO2 breaking through to pr %)
WVF of inj. water (m3/std-m3) - Cell DA84
Produced
GVF of reservoir gas (m3/std-m3) - Cell AD75
GOR_OS Solution gas ratio of oil ratio Cell F33
WVF of prod. water treatment to reinjection - Cell DQ84
FFV of crude oil in the reservoir (bbl/STB) - Cell F34
Volume weighted avg. GVF of Inj. gas (GFIR) + WIR (Inj. water in STB) = GVF of gas in reservoir (GOR-Solution gas-oil ratio) + WVF of Brine (*1.1WIR*) + FVF of crude oil in reservoir (1)
If the primary inputs are missing for WOR and WIR, the OPGEE model first calculates WOR based on the age of the field and then calculates WIR which may not be the case for the CO2 development case.
Also, the left-hand side of the above equation can be used to create a new variable WAG ratio = Volume of water inj./Volume of gas injected which has a major impact on the CI of CO2-EOR oil.
For Gas flooding calculation, OPGEE calculates using the same water flooding assumption WIR = 1 + WOR which can be better calculated given the following information and assumption.
The limitations in using the current equation for WOR and then WIR for CO2-EOR development.
Based on the historical CO2 floods, it has been shown that WOR > WIR.
Also, the above OPGEE default is meant for water flood as stated in the documentation, but even when gas flooding is set, the WOR and WIR are still calculated in the same way which underestimates WOR and WIR. The following equation is to be used to calculate WOR and WIR assuming for eg. WOR = 1.10 WIR (this needs to be studied further to quantify by how much water produced volumes are greater than injected volumes in specific for miscible CO2 floods) with the following assumptions:
Assuming CO2-EOR floods VRR =1 (Injected reservoir volumes = produced reservoir volumes)since the reservoir pressure is maintained and to be maintained > MMP for miscible floods.
Injected
Produced
Volume weighted avg. GVF of Inj. gas (GFIR) + WIR (Inj. water in STB) = GVF of gas in reservoir (GOR-Solution gas-oil ratio) + WVF of Brine (*1.1WIR*) + FVF of crude oil in reservoir (1)
If the primary inputs are missing for WOR and WIR, the OPGEE model first calculates WOR based on the age of the field and then calculates WIR which may not be the case for the CO2 development case.
Also, the left-hand side of the above equation can be used to create a new variable WAG ratio = Volume of water inj./Volume of gas injected which has a major impact on the CI of CO2-EOR oil.