Further Enhanced Oil Recovery By Chemical Flooding After Polymer Flooding

Polymer flooding is one of the most important tertiary oil recovery methods.Because a lot of residual oil is still remained in reservoir after polymer flooding,so how to improve the oil recovery after polymer flooding become urgent for most of the oil fields.In this study,B-PPG/polymer flooding,B-PPG/polymer/surfactant flooding and ultra-high molecule polymer flooding for enhance oil recovery after polymer flooding were conducted by designing rheological tests,single sandpack flow tests and heterogeneous dual-sandpack flooding experiments.The results shows that:B-PPG possesses viscoelastic properties,and the elasticity is much more obvious than the viscosity.By mixing the B-PPG and polymer,the obtained combined system has both the elasticity property of B-PPG and the high viscous property of polymer.Besides,the suspension ability for B-PPG can be improved.B-PPG can flow in porous media through the blocking-deforming-passing mode,and plugging the pores and throats to increase the resistance factor.Because the selective blocking property and flow diversion ability of B-PPG,combined by the high viscous property of polymer,B-PPG/polymer system has a good performance control ability and can improve the injection profile file for the heterogeneous formations,and thus increase the sweep efficiency to improve the oil recovery after polymer flooding.When the system has a 1:1 B-PPG to polymer ratio,and 2500 mg?L~-11 concentration,the flooding process has a best economic results.Adding surfactant to the B-PPG/HPAM system can reduce the interfacial tension of oil and displacing fluid,resulting in high displacement efficiency and oil recovery.The most economical usage of surfactant is 0.4 wt%.Ultra-high molecule polymer possesses a high molecular weight and a more complex molecule entanglement,therefore it has a higher viscosity than the conventional polymer,and can improve the water-oil ratio to increase the sweep efficiency and improve oil recovery.when 2500 mg?L~-11 concentration,the flooding process has a best economic results.Compared with three systems,B-PPG/HPAM/surfactant is the best way.