Waterflooding is not very effective in highly fractured oil-wet carbonate reservoirs. One of the ways to recover oil from such reservoirs is to use surface active agents to alter the wettability of the rock and recover oil through counter-current imbibiton or gravity drainage. Dilute anionic surfactant solutions (<0.1 wt %) have been identified to recover 40-70 % OOIP recovery in laboratory scale. One of the limitations is that these processes are relatively slow. This paper discusses the parameters that can improve the oil recovery rates from the oil-wet fractured carbonates. Five parameters are discussed in this work which are found to increase oil recovery rates: extent of wettability alteration, interfacial tension (IFT), temperature, fracture density in the reservoir and pressurizing.

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