DOI: https://doi.org/10.55373/mjchem.v28i4.227

Keywords: Cationic surfactants, wettability, spontaneous imbibition, core-flooding, EOR

Abstract

The chemical enhanced oil recovery (CEOR) is the process of using surfactants, alkalis, polymers for increasing oil production in the tertiary production stage. Cationic surfactants were used to minimize the IFT and altering the wettability of carbonate rocks which is essential for facilitating the mobilization of the trapped oil from porous media. The capability of cationic surfactants will depend on many factors including the surfactant concentration, salinity, temperature, and surfactant chain length. Tetramethylammonium chloride (The alkyltrimethylammonium, R-N(CH₃)₃) is one of quaternary ammonium compounds which has a short chain length. TMAC can tolerate the harsh reservoir conditions (high temperature and high salinity). Using the high concentration of TMAC can ensure sufficient monomer availability to induce the IFT reduction and wettability alteration and can enhance the oil recovery by ensuring sufficient monomer availability. In this experimental work, we used TMAC as an EOR fluid. Using high concentration of TMAC (5000 ppm) which prepared in high salinity water (seawater) for chemical EOR and compare the results with low concentration to figure out the role of increasing concentration of short chain surfactant in EOR. Two brines (formation water & seawater) and two Indiana limestone core samples were used for Spontaneous Imbibition and surfactant flooding experiments under reservoir conditions which mimic the Middle East reservoir conditions. FTIR, IFT, and ICP were performed to characterize the surfactant. Spontaneous Imbibition was also used to confirm the ability of TMAC to change the wettability at high concentration. The results of spontaneous imbibition showed that using high concentration of TMAC (5000 ppm) can alter the wettability more than the low concentration and gave about 16% of accumulative oil recovery. While the core flooding outcomes revealed that the TMAC at concentration of (5000 ppm) increased oil recovery about 24% when using it at tertiary stage. The total oil recovery of core flooding test was about 74% of OOIP. The FTIR test was carried out for TMAC powder and TMAC/SW solution with rock. FTIR results showed a slight change in TMAC bonding when added to the rock. Furthermore, the ICP analysis of effluent showed a slight increase in Ca⁺² concentration alongside with a slight decrease in Mg⁺² concentration.