CORE FLOOD STUDIES TO EVALUATE EFFICIENCY OF OIL RECOVERY BY LOW SALINITY WATER FLOODING AS A SECONDARY RECOVERY PROCESS

Various researches on laboratory and field scale illustrate that manipulating the ionic composition and the ion concentration of injected water can affect the efficiency of water flooding and the interaction of injected water with rock and other fluids present in porous media. The objectives of this paper are to investigate parameters that affect low salinity water flooding; mainly the effect of injecting water salinity on and the potential of low salinity water flooding for oil recovery in secondary recovery mode are studied. The effect of pH and differential pressure across the core are used to explain the mechanism of fine migration phenomena. The recovery results of formation water injection were compared for the seawater, formation water with a salinity of 0.1 and 0.01, and when divalent ions were removed from the formation water with a salinity of 0.01 to investigate the effect of divalent ions on oil recovery. Different types of crude oil were used for investigating the effect crude oil properties on oil recovery. Seawater injection resulted in lowest oil recovery of 2.6% and the reduction of water salinity of formation water from 0.1 to 0.01 resulted in an improvement of 4% and 7.7% in oil recovery respectively. Removing divalent ions from the injected water decreased the improving effect of low salinity water flooding. In addition, both types of crude oil responded to low salinity flooding and no straight correlation was seen between acid number and the improving effect of low salinity water flooding.