Synergistic Effects of Different Ions on the Surface Phenomena During the Smart Water Injection in Composite Reservoirs

Abstract

Today, the most of the oil reservoirs are in their second half of life, and most of their oil has been mined while still, over 50% of the oil remains in the reservoir, which cannot be produced on their own. For this reason, to produce the remaining oil, chemical oil recovery methods can be used, including smart water (engineering water) injection, which can be used for improving the oil recovery process. The main mechanism is mainly the change in the wettability of the reservoir rock to water-wet and reduction of oil-water interfacial tension (IFT) to some extent. The smart water formulated, the single and binary systems preparation method is divided into two groups: in the first group salts (single systems) such as NaCl, KCl, MgCl₂, CaCl₂, Na₂SO₄, MgSO₄, CaSO₄, and K₂SO₄ are made each individually at concentrations of 1,000,2,000,4,000 and 10,000 ppm. For the second group (binary systems), the investigated salts divided into two parts of chlorates and sulphates then combine each of the chlorate salts with different sulphates ions with equal ratios (1,000+1,000, 2,000+2,000, 4,000+4,000, and 10,000+10,000 ppm) in distilled water. Then, the effects of the dissolution of these salts on interfacial tension and contact angle between water, oil, sandstone, and carbonate rocks were studied. The optimum point for the solution of CaSO₄+MgCl₂ at the concentration of 4,000+4,000 ppm for both sandstone and carbonate rock were obtained. Finally, the optimum point was used for the flooding test and the result of flooding test for the carbonate rock reduces the OOIP up to 51.9%, and for the sandstone rock, the reduction is 60.2%.