Phase Behavior & Core Flooding of Low Acid Number Crude Oil for Application in Alkaline EOR

Alkaline flooding is one of the most promising methods to be applied in recovering residual oil in the reservoir. The process behind this method is, when the alkali being injected in the reservoir, it reacts with the naturally occurring acids in the crude oil and produce soaps or in-situ surfactants. The produced surfactants will help in removing oil from the rock surface and escapes from the pore easily. A proper study in the characteristic of the crude oil and reservoir before injecting the alkali can also change the wettability of the rock to the favorable condition. The oil components that react with alkali are not specifically known, although acid number is cited as one. However, the current application of alkaline flooding in the industry is limited to the reservoirs with high acid number crude oil although many there are no proven correlation which shows that acid number is related to the surfactant produced. In this study, two different types of crude oils from Dulang field, high acid number crude oil and low acid number crude are tested with two different alkali, namely Sodium Hydroxide (NaOH) and Sodium Carbonate (Na2CO3). Both crude oils and alkalis are tested for compatibility with various salinity and alkaline concentration. Then, the interfacial tension was measured between the alkaline solution and crude oil to observe the IFT reduction. Finally, core flooding is done with optimum concentration of alkaline with both high acid number crude oil and low acid number crude oil with the best selected alkaline, Na2CO3. The results shows the possibility of alkaline flooding in low acid number crude oil and increase in the application of alkaline flooding in potential reservoirs.