Abstract: In light of the fact that following implementation of water quality improvement technology, water injected in oilfield has become alkalescent water (pH≥8.0) from slight acidic water, Mazhai Wei-95 Block reservoir is of high salinity, Ca²⁺, Mg²⁺ con-tents and low acid value in Zhongyuan oilfield, this paper presents a concept of alkalescent water compound flooding for EOR, adding salt-resisting surfactant into injected alkalescent water. By testing resolvable property of the surfactant in alkalescent water and oil-water interfacial tension in compound system, two compound flooding systems (JJ867 and JJ869) suitably applied in Mazhai Wei-95 Block reservoir production conditions are prepared. The oil displacement experiment shows that using these two systems can get incremental oil recovery factors of 9.3% and 14.3%, respectively.

Key words: salinity, alkalescent, chemical flooding, surfactant, EOR