The efficacy of carbonated water
injection (CWI) is associated
with weak CO2 absorption in water, and the resulting CWI
does not meet the requirements of controlled CO2 mobility
and enhanced oil recovery (EOR). High molecular
weight oilfield polymer, e.g., polyacrylamide (PAM), is water-soluble
and often used in water shut-off and mobility control applications.
Thus, in this study, PAM, with concentrations (0.5, 1, and 2 g/L),
as a viscosifier is used to improve the CO2 absorption
capacity of water for possible implementation in CWI applications.
PAM with intermediate concentration (1 g/L) was favorable for enhanced
CO2 absorption with a retention period of 4 days in water.
With high PAM concentration (2.0 g/L), CO2 absorption reduced
and gas in the form of globules moderately absorbed in the upper layers
of P-1 solution, resulting in a significant amount of aqueous phase
left unabsorbed by CO2. At high PAM concentration, enough
number of PAM chains were available to interact with CO2 and, as a result, solution received premature gelling that resisted
further entry of CO2. The effect of stirring on CO2 absorption showed that the rate of stirring increases the
amount of CO2 absorbed in P-1 solution. These observations
were supported by rheological data which showed that CO2 absorption reduced the viscosity of the P-1 solution, and the decrease
in viscosity is directly proportional to the amount of CO2 absorbed. Finally, oil recovery experiments were performed using
P-1 solution with and without CO2 and compared with water.
The oil recovery was found to be higher for P-1 solution prepared
with 600 rpm. Thus, this study highlights the application of relatively
common oilfield polymer PAM (⩽ 1 g/L) for enhanced CO2 absorption and improved oil recovery than conventional CWI, which
recommends use of polymer-enhanced carbonated water injection (PE-CWI)
in oil and gas industry.