An experimental study of the low salinity Smart Water - Polymer hybrid EOR effect in sandstone material

作者：Torrijos Ivan D Pinerez; Puntervold Tina; Strand Skule; Austad Tor; Bleivik Tord H; Abdullah Hakar I

来源：Journal of Petroleum Science and Engineering, 2018, 164: 219-229.

DOI：10.1016/j.petrol.2018.01.031

Previously reported experimental work has shown positive oil recovery effects by combining low salinity brine with polymer for injection into sandstone cores. The extra oil recovered by the combination of the two EOR methods was termed a "Hybrid EOR effect".
The experimental work performed in the present study assessed the potential of combining low salinity (LS) Smart Water injection with polymer (P) flooding; LSP flooding. Dramatic improvements in the EOR effect were observed when combining LS in secondary mode with polymer injection in tertiary mode.
Secondary LS injection gave 59 % OOIP after 1 PV injected, which is an outstanding result compared to secondary formation water (FW) injection reaching only 35 % OOIP after 1 PV, and an ultimate recovery of 40 % OOIP after 2.5 PV. The ultimate recovery with seawater (SW) in secondary mode was 44% OOIP, showing only a slightly better performance than FW, but poorer efficiency than the ultimate LS brine recovery of 64 % OOIP.
In comparison, the ultimate recovery with secondary LSP injection was 66 % OOIP. The displacement front was stable and fast, but it did not give a substantial increase in oil recovery in comparison to the secondary LS injection. Tertiary LSP injection after secondary LS injection gave the highest oil recoveries with a total hybrid EOR effect of 86 % OOIP. All tertiary LSP floods gave improved displacement stability with EOR effects of similar to 20 % OOIP. The positive EOR effects are a result of redistribution of oil within the pore space after wettability alteration with the Smart Water. Oil attached to the mineral surface has low mobility, but at more water-wet conditions a new fraction of mobile oil, which is more easily mobilized with a polymer solution, is created (Wang et al., 2001).
The combination of Smart Water with polymer flooding appears to have a huge potential for future EOR applications. Field development strategies for new sandstone reservoirs should include wettability alteration and redistribution of oil within the pores by Smart Water and improved displacement efficiency with polymer for optimized EOR to lowest cost.

• 出版日期2018-5