Modification Of Langmuir Equation To Predict The Retention Of Sulfonated Polyacrylamide Polymer In Polymer Flooding

Polymer flooding is a process in Enhanced Oil Recovery (EOR) to improve volume of oil recovered. To improve the efficiency of oil recovery, water-based polymer, e.g hydrolyzed polyarcylamide(HPAM) and xanthan are injected in the water flooding process. It helps to reduce the water to oil mobility ratio, resulting higher oil recovered. Nowadays, synthetic polymer, e.g. HPAM, is the most commonly used in polymer flooding but it has some limitations. HPAM has limitation at high temperature above 75oC and cannot be applied under high salinity. The other limitation that can influence and affect the performance of polymer flooding is retention. Retention is summation of mechanical entrapment, hydrodynamic retention and adsorption of polymer in porous media which contribute to reduce of polymer flooding efficiency. It is believed that by using different copolymer of polyarcylamide in polymer flooding, the retention effect may be reduced. By replacing some of carboxylate group of HPAM with another monomer,e.g. sodium salt of acrylic acid and 2-acrylamido-2-methylpropane sulfonic acid (AMPS), effect of retention seem to be reduced.
The main aim of this study is to evaluate Langmuir equation whether the equation is applicable on sulfonated polyacrylamide polymer or not. The equation was analyzed and fitting parameters were extracted by using non linear fitting function of MATLAB software. Non linear fitting was used to tune the model parameters in order to obtain best fitting parameters. The result showed poor prediction ability of Langmuir isotherm if sulfonated polyacrylamide is used. The equation has already taken into account the present of divalent ions, permeability, temperature and polymer concentratiton but did not consider molecular weight and sulfonation degree parameters. Minitab software has been used to determine the significant of these parameters on the retention amount. The measurement was verified by using p-value and Pearson coefficient results. There was clear evidence that showed sulfonation degree has significant effect on retention amount of sulfonated polyacrylamide polymer in polymer flooding. Very low p-value (0.00) was achieved, which makes this parameter was reliable to be taken into account in modifying the Langmuir isotherm equation. The model outputs were validated by calculating the regression coefficient of MATLAB software.