CO2 Sequestrated EOR

[WAG; Sweep Efficiency; MMP]

Which ONE of the following remains to be predominantly responsible/sensitive for EOR by CO2 sequestration?

(a)        When CO2-EOR operations take place in oil reservoirs, where, the relatively lesser expensive water-flooding has already been implemented; and where, the remaining oil saturation in the post-waterflood reservoir still remains to be significant (preferably, with more than 50% of OOIP)

(b)       When CO2 flood operation remains with a pipeline that delivers CO2 to field @ pressure greater than 1300 psi; and @ density greater than 6 pounds per gallon.

(c)        When CO2 is directed to injection wells (having the best well pattern) that optimizes the areal sweep efficiency of the reservoir (and, which involves the changing patterns of injectors & producers with time, and, which essentially ensures that the concentration of oil would keep increasing as the oil bank reaches the producing wells).

(d)       When CO2 remains miscible (the ability of CO2 to mix with oil, in all proportions; becoming mutually soluble) with the residual crude oil (above Minimum Miscibility Pressure); and in turn, which makes the physical forces holding CO2 and oil phases apart (IFT) effectively disappears (which enables CO2 to displace oil with ease).

(e)        When CO2 remains less expensive than other similarly miscible fluids.

(f)          When CO2 is injected in a highly compressed form, whereby, the density of CO2 becomes large.

(g)       When the residual crude oil contains a significant fraction of light hydrocarbons (a low density crude oil); and which remains favorable for CO2/Oil miscibility.

(h)       When CO2 is injected into a reservoir condition, where the increase in reservoir temperature does not lead to the reduction of CO2 density; and which remains favorable for CO2/Oil miscibility.

(i)          When the pressure of an oil reservoir has significantly become depleted (but, in the absence of requiring re-pressurization by water injection).

(j)          When injected CO2 gets dissolved in the residual crude oil, leading to swelling of the oil, which reduces oil viscosity, while improving the displacement process.

(k)       When CO2 injection gets alternated with volumes of water (WAG, where separated produced water can be treated and re-injected, and thus, alternating with CO2 injection – that enhances sweep efficiency), which helps to mitigate the tendency for the lower viscosity CO2 to finger its way ahead of the displaced oil (because, once the injected CO2 breaks through to the production well, then, any CO2 injected afterwards, will follow that path, and thereby, reducing the overall efficiency of the injected fluids to sweep crude oil from the reservoir).

Suresh Kumar Govindarajan Professor (HAG)    IIT-Madras

https://home.iitm.ac.in/gskumar/

https://iitm.irins.org/profile/61643