A comparative study on enhancing oil recovery with partially hydrolyzed polyacrylamide: Emulsion versus powder

In China, powders of partially hydrolyzed polyacrylamide (P-HPAM) have been extensively used in chemically enhanced oil recovery (cEOR) processes. However, the relatively longer dissolution time of P-HPAM and high investment in surface facilities diminish the profit. Here, we compared the properties between P-HPAM and emulsion HPAM (E-HPAM) with similar molecular weight of 1.5 x 10(7) g/mol at polymer concentration of 1000 mg/L under a simulated Daqing Oilfield reservoir. We found only 20 min was needed to completely dissolve E-HPAM, 75% less time than for P-HPAM. The apparent viscosity of E-HPAM reached 69.6 mPa center dot s, 26% higher than that of P-HPAM. Sheared at 7000 rpm for 30 s, 73.8% viscosity retention was maintained for E-HPAM solution, 13.7% higher than that of P-HPAM solution. After 90 days of thermal aging, E-HPAM solution had 72.8% viscosity retention, 15.2% higher than P-HPAM. After being adsorbed in a sand package, E-HPAM and P-HPAM solutions had 87.0% and 83.2% viscosity retention, respectively. The interfacial tension (IFT) between E-HPAM solution and Daqing oil could reach 15.3 mN/m, 75.1% lower than that of the P-HPAM solution with Daqing oil. After 1.2 PV of polymer solution was injected, E-HPAM solution got an oil recovery factor of 24.1% (OOIP), 10.0% higher than that of P-HPAM under identical conditions. Both polymer solutions could propagate smoothly in porous media without plugging. In the field trial of 63 wells, after 0.098 PV of E-HPAM solution was injected within nine months, the injection pressure increased by 1.3 MPa, and an interim recovery factor of 0.58% was obtained.

Automated summary

Compared with P-HPAM, E-HPAM showed shorter dissolution time, higher viscosity retention, lower interfacial tension, and higher oil recovery factor in a simulated Daqing Oilfield reservoir.