Laboratory investigation of the injectivity of sulfonated polymer solutions into carbonate reservoir rocks

The injectivity of sulfonated polymer solutions in carbonate reservoir rocks was investigated to evaluate the performance and feasibility of the polymer in the porous media under reservoir conditions. A sulfonated Polyacrylamide with a sulfonation degree of 25 mole% was selected for this study. Polymer solutions at 0.1 wt% and 0.2 wt% in seawater were injected into carbonate core plugs with a permeability ranging from 100-600 mD at reservoir temperature and pressure. Two critical parameters, the resistance factor and residual resistance factor, were obtained in the tests. The resistance factor represents a quantitative measure of the mobility reduction during the propagation of the polymer solution in the porous media, while residual resistance factor is a measure of permeability reduction after the polymer treatment. The resistance factor is 5-8 at a flow rate of 0.5cc/min for 0.1 wt% polymer solution. The residual resistance factor is 1.24-1.34 for seawater injection after the polymer injection. Meanwhile, the resistance factor is 50-65 at a flow rate of 0.5cc/min for 0.2 wt% polymer solution. The residual resistance factor is 1.48-2.17. It is found that resistance factor increases significantly with flow rate, while residual resistance factor decreases with flow rate. The investigation of adsorbed polymer layer based on the permeability reduction provides insights into the performance of the selected polymer in the carbonate cores.