Comparative Evaluation of the Performance of Synthetic Polymer and Biopolymer as a Means of Enhanced Oil Recovery Method

Abstract

After regular primary and secondary recovery treatments with ideal oil production no longer occur, enhanced oil recovery methods are introduced to produce the “leftover” oil in reservoir formations. Among the enhanced oil recovery (EOR) methods, polymer flooding is regarded as the most common and widely used treatment globally. By adding water-soluble high molecular weight polymers into water, viscous fluids This work aims to analyze the performance of two types of polymers as a means of EOR by comparing their rheological properties and laboratory 1D sandpack flooding studies. It compares the performance of these polymers against the performance of waterflooding as a secondary recovery method. The synthetic polymer partially hydrolyzed polyacrylamide (HPAM) Flopaam 3630S and biopolymer diutan gum are selected for this study, where higher recovery factors are observed than waterflooding. For rheological studies of both polymers, a cone/plate viscometer was introduced to investigate the apparent viscosity of polymer solutions over varying influential factors at various shear rates. The findings show that the biopolymer solution demonstrated a much larger viscosity loss compared to the HPAM polymer solution over the shear rate at the same concentration. Polymer concentration and temperature both presented a positive impact on viscosity loss, as the higher their values, the more the viscosity decreased. A larger viscosity deduction was observed when the ions concentration increased before the limitation of 1.0 wt%, whereas the divalent cation (Ca2+) presented a greater degree of effect than the monovalent one (Na+). Nine sets of 1D sandpack flooding experiments were carried out for polymer flooding with different saturated oils ranging from 500 mPa.s to 2,000 mPa.s, various concentrations of HPAM solutions (1,000~4,000 ppm), and a 2,000 ppm biopolymer solution with various injected pore volumes (0.2 ~ 0.5 PV). All tests were conducted with 1.0 wt% NaCl brine at room temperature (22◦C) at a flow rate of 1 cc/min. The ultimate oil recovery factor and water cut variation were recorded with respect to the injected fluid volumes. Overall, biopolymer presented a better performance compared to HPAM in most aspects. The ultimate oil recovery of biopolymer was 20% more than that of HPAM, and biopolymer also significantly altered the mobility ratio and improved the water cut. Polymer concentration and the injected polymer volume indicated a positive effect on oil production with the increase of their values. However, they did not ensure a significant improvement in production during polymer floods. A comparison between the results of varied oil samples suggested less impact on the performance of polymer flooding, although more viscous oil generated less production.