Further enhanced oil recovery by branched-preformed particle gel/HPAM/surfactant mixed solutions after polymer flooding in parallel-sandpack models

Abstract

How to further sweep residual oil from unswept areas is crucial to enhance oil recovery after polymer flooding, which is widely used. Branched-preformed particle gel (B-PPG) is a newly developed chemical agent for enhanced oil recovery in heterogeneous reservoirs. In this paper, B-PPG/HPAM/surfactant mixed solutions were investigated to further enhance oil recovery after polymer flooding in parallel-sandpack models by core flood test. First of all, laboratory experiments about fractional flow and enhanced oil recovery were performed to determine the optimal composition and concentration of B-PPG and HPAM mixed solutions. The results show that B-PPG/HPAM mixed solutions have higher abilities to adjust fractional flow in parallel-sandpack models than HPAM alone when the mass percentage of B-PPG is larger than 50%. Moreover, B-PPG/HPAM mixed solutions can displace more oil in low permeability sandpacks and the total oil recovery is the highest when the mass percentage of B-PPG is 50%. The concentration also has a great effect on fractional flow and oil recovery of B-PPG/HPAM mixed solutions. The ability of adjusting fractional flow and enhancing oil recovery increases with increase in concentration. Furthermore, the presence of surfactant in the flooding solutions can further enhance total oil recovery, especially that in high permeability sandpacks, and has no obvious effect on the ability to adjust fractional flow. When the permeability ratio of the parallel sandpacks becomes 1 : 9, the B-PPG/HPAM/surfactant mixed solutions still have strong abilities to adjust fractional flow and enhance the oil recovery. This is because the presence of a surfactant can improve displacement efficiency, while B-PPG and HPAM can enhance sweep efficiency.