The addition of natural and synthetic surfactants during chemical flooding recovers oil originally trapped by capillary forces through the reduction of the interfacial (adhesive) tension between the aqueous and oleic phases. As the interfacial tension reduces, the trapped oil droplets are mobilized forming a continuous oil bank thereby reducing the amount of residual oil saturation. The objective of phase behaviour is to determine the optimum salinity and to select the best compatible chemical composition for a specific application that can effectively enhance oil recovery. This study seeks to assess chemical compatibilities between alkaline –surfactant systems in the presence of calcium and magnesium ions; analyse synergy between alkali-surfactant slugs and crude oil to enable us to design an optimal low-cost, environmental friendly alkaline and surfactant floods for enhanced oil recovery. This is based on an understanding of fluid-fluid interactions. We conducted phase behaviour tests on selected local surfactants (AlkaSurf X, Moringa), bio-ethanol, local alkali (potash) and simulated formation brine. Aqueous stability and salinity scan experiments were conducted to determine the compatibility of the Alkaline–Surfactant systems with brine. Solutions free of precipitation were used for the interfacial-tension and phase behaviour analysis. Salinity scan results were used to calculate the solubilisation ratio and optimal salinity. Results indicate that the local Alkaline-Surfactant systems are highly tolerant of divalent ions. Also, results from pipette test showed that AlkaSurf X and Moringa alone attained a Type II (-) microemulsion, however, the addition of potash and co-surfactant at a controlled pH and concentration exhibited optimal salinity and a Type III microemulsion. This study shows that certain local alkali and surfactant can enhance oil recovery, even under harsh conditions, thus eliminating the use of harmful chemicals and need for brine softening processes which adds to the overall cost.

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Alkaline Surfactant Polymer (ASP) local oil recovery process has shown great potential in enhanced oil recovery (EOR). The recovery percentages are encouraging. The fact that these reagents are locally and cheaply sourced is also advantageous. The technique can be successfully applied in producing oil left in reservoirs after primary and secondary recovery process has been exhausted. The reagents used for this work include Irvingia Gabonensis, Lecithin and Palm Bunch Ash (PBA). Irvingia Gabonensis is granulated wild mango seeds (Ogbono, a biopolymer) used as polymer. It has similar characteristics with the xanthan gum that is already in use. Lecithin is a phospholipid and also a surfactant extract from soya bean. PBA is an alkali, and also an agricultural waste product. The reagents were used individually and in combination. Unconsolidated sand was used in the experiment. The appreciable oil recovery from the experiment buttresses the essence of lowering interfacial tension by the alkali through in-situ saponification to recover 25% oil in place (OIP). The surfactant in this experiment lowered interfacial tension to release more oil out from the sand pores and thus recovered 23.3% OIP. The polymer used increased the mobility and gradually swept the oil trapped in the pores to increase oil recovery by 22.7% OIP. A combination of the reagents used shows that the ASP flood gave a percentage recovery of 27.7% ROIP and an incremental oil recovery of 17.9% above water flooding.

Several techniques have been deployed to enhance oil recovery. Some have given good results while there is still the possibility that some materials that have not been tried might also have the capacity to enhance recovery. The underlying motivation for this study therefore is to find out the capacity of local materials to enhance oil recovery. Alcohol (palm wine) and water mixture and alcohol (palm wine) and starch mixture were used in various ratios to find out the ideal ratios that recovers oil most from sands. Experimental results show that a mixture of alcohol and water and alcohol and starch can enhance oil recovery. For alcohol and water, oil recovery increased with an increase in alcohol content of the mixture. This could be attributed to reduction of interfacial tension between oil and water. For alcohol and starch, the ideal ratio of 1:1 gave the highest recovery. Beyond this ratio, oil recovery was observed to be reduced. The good result may have resulted partly from reduction of interfacial tension and partly as a result of increase in the viscosity of the displacing fluid.