Dear Watheq,

There are a few reviews of CO2 flooding. These are mainly SPE publications (Conference papers, Journal and monograph). I am not up to date with this literature except for the phase behaviour.

My impression is that CO2 flooding has mainly successful as TAX flooding. That is when the recovered oil had Tax reduction (aiming at encouraging enhanced oil recovery projects). With extremely low oil prices, I guess that enhanced oil recovery is not a hot topic now.

While obviously asphaltenes precipitation is a problem, it is possible that the main problem is actually an increase in crude viscosity, just before asphaltene precipitation occurs. Hence this could be an in depth reservoir problem rather than a plugging due to asphaltene deposition (skin formation around production wells). 

Mico Hirschberg

Your question is just as valid for any kind of flood or artificial pressure support enhanced recovery project.  The main difference with CO2 is that it is miscible with oil and acts like a solvent in the reservoir.  Thus CO2 floods generally recover a higher percentage of oil than water floods. As the saying goes oil and water don't mix.

Using CO2 brings additional corrosion problems to tubing. Extracting CO2 and compressing CO2 for injection is not cheap. Some CO2 enhanced recovery projects did experience problems with injectivity reduction. So there are quite significant costs involved with CO2 flooding. Also the use of classical injection is limited to specific cruces in which you achieve multiple contact miscibility, these are relatively light oils. For heavier crudes you can consider alternative injection methods (local fast injection forcing strong fingering(which increases the contact surface oil/CO2), shutting down for mixing and then production by the injection well. There is a patent by Shell on this method).

CO2 inyection can be affectated by the presence of minerals. Take into account that CO2 can be state in aquos and gas phase.

The thermal issue in CO2 flooding particularly through the near wellbore and reservoir is critical for Reservoir mechanical performance, along with the resulting cooling come other major changes to the rock such as a decrease in compressive strength and loading. It can also lead to changes in the petrophysical properties of the reservoir inducing a "damage" that is nothing else but a change in porosity and permeability, I hope it helps.

CO2 EOR process is a very complex one. One of the main factors affecting his efficiency in a heterogeneous reservoir is the early breakthrough of CO2 due to the areal and probably vertical variations of the permeability so you will need to have in place a very robust surveillance plan to control the CO2 injected. Early production of CO2 will translate in the need of enough capacity of CO2 processing from the beginning of the flood which will affect your economics. Another factor that affects the CO2 performance is the lost of the miscibility state in the reservoir and as a result lower recoveries than expected. There are plenty of SPE papers that mentioned these and other factors and I'm sure your University has a license you can use to get these papers. Check for CO2 in carbonates. Hope this helps