Synthetically prepared low-salinity brines are usually used for mechanistic and improved oil recovery studies in carbonate rocks. However, in actual onshore field applications, using nearby produced water with low or seawater-like salinities could potentially yield optimized waterflooding economics. In this work, field samples from Central Kansas Uplift oil production formations were acquired and tested for the potential increase in oil production from mature oil reservoirs. Geochemical compatibility testing of fluid-fluid interaction between the hypersaline produced water (PW-1) from Lansing Kansas City reservoir and seawater-like produced water (PW-2) from the Arbuckle formation showed no evidence of potential scale formation. Furthermore, seawater-like PW-2 altered the limestone rock wettability represented by lowering the contact angle from 148° (oil-wet) for PW-1 to 119° (intermediate wet) for PW-2. Wettability alteration was further supported by the Amott-Harvey index. At the oil-brine interface, equilibrium interfacial tension slightly increased from 8.35 mN/m2 for PW-1 to 10.87 mN/m2 for PW-2. However, the surface elasticity was calculated to increase from 43.3 mN/m2 to 74.8 mN/m2 for hypersaline PW-1 and seawater-like PW-2, respectively, indicating better stability at the oil-brine interface, which could reduce crude oil snap-off and improve sweep efficiency. Approximately 6.7% incremental recovery due to the injection of seawater-like PW-2 was observed in the secondary mode. Therefore, the use of geochemically compatible seawater-like produced water with carbonate rocks hosting hyper-saline water could improve oil recovery by altering the rock wettability and suppressing crude oil snap-off, hence serving as a viable economic option for mature oilfields.

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