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arbrandt / OPGEE

Oil Production Greenhouse Gas Emissions Estimator
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Recycled CO2 is missing? #214

Closed smasnadi closed 4 years ago

smasnadi commented 4 years ago

I could not understand one item for CO2-EOR mode of OPGEE. I think the current version of OPGEE misses large GHG emissions associated with CO2 recycling and re-injection! Here is the issue

Assuming: GFIR: 10,000 scf/bbl and the perc. of newly acq. CO2=40%

This means that 40% of GFIR comes from external fresh CO2 (which is accounted in "Gas flooding comp." sheet). There are also two other internal sources of CO2 that come out of reservoir:

1- the produced associated gas CO2 (which is fully accounted in "Separation" sheet cell L18)

2- the recycled CO2 (60% of GFIR): Where is this stream in OPGEE calculations? This stream should be added to the associated gas stream and be passed through dehydrator, membrane/R-H, and AGR units and finally get injected through "CO2 Reinjection Comp." sheet. What is happening is that in the current version, only the associated gas is getting reinjected to the reservoir.

Another minor issue is that: for the "Gas flooding comp." sheet to account the fresh CO2 injection, we need to subtract the associated gas CO2 that comes out of reservoir from that 40% and then flood the subtracted number to the reservoir.

smasnadi commented 4 years ago

I talked with Adam and seems that the recycling CO2 was missed from the entire OPGEE calculations. So here are the changes I made in OPGEE: I added a new stream in the Flow Sheet (stream 91) to introduce the recycled CO2 to the system (that 60% in the above comment example) and made appropriate modifications to accommodate this change. Here are the changes made in different sheets and corresponding cells: Sheet name:cell address Flow Sheet: O100 & column CR Separation: L18 Reservoir: H18 & S18 Reservoir: column I from row 8 to 32 Reservoir: rows 79 and 80 are added Gas Flooding Comp: E18 (to address the "minor" issue explained above)

@qlangfitt: I ran OPGEE for Lula (field 8) and seems that everything works well and the numbers make sense. I need second eyes to double-check the CO2-EOR changes. Can you review it?

@arbrandt: Please see my comment on issue #196. If we close #196, we should be done with CO2-EOR issues. Thank you!

qlangfitt commented 4 years ago

Flow Sheet: O100 & column CR

Separation: L18

Reservoir: H18 & S18

Reservoir: column I from row 8 to 32

Reservoir: rows 79 and 80 are added

Gas Flooding Comp: E18 (to address the "minor" issue explained above)

Finally, when you say the results for Lula make sense, do you mean it is in agreement with OPGEE 2.0?

smasnadi commented 4 years ago

Separation: L18 So the gas composition in the process units is basically a combination of the reservoir naturally occurring associated gas + recycled CO2 that is not sequestrated (L18). The new CO2 injected only affects the gas flooding compres. sheet which is somehow detached from the other process units (see the Flow Sheet).

Gas Flooding Comp: E18 My understanding is that GFIR is the total cumulative gas that is injected to the reservoir (new CO2 and recycled CO2). So if additional CO2 (naturally occurring produced CO ) is injected along with the recycled CO2 (CO2-reinjection comp. sheet), we need to subtract that additional CO2 from the fresh CO2 that is injected to keep the total CO2 injected equal to GFIR. Does that make sense? Probably a better way to calculate E18 is to simply subtract the total co2-rinjected (from CO2 Reinj. Comps. sheet) from the total GFIR. See the updated E18.

No, I meant the flooding numbers now makes sense and the fact that the new GHG emissions is higher than before for CO2-EOR. Didn't have a chance to compare with 2.0. In 2.0 we had the same recycling issue, but I fix it in the last version before moving to 3.0