Evaluation of petroleum as extractor fluid in liquid-liquid extraction to reduce the oil and grease content of oilfield produced water

This work aims to evaluate the use of petroleum as a solvent in the liquid-liquid extraction of oil and grease content from oilfied produced water. Initially, tests were performed with synthetic effluent, using cyclohexanecarboxylic acid as model compound through the study of physical-chemical parameters: pH, temperature, stirring speed and time, petroleum type and concentration, and initial concentration of naphthenic acids. Afterwards, the process was evaluated for the removal of oil and grease content from a real oilfield produced water sample. The pH and petroleum concentration proved to be significantly influential in removing cyclohexanecarboxylic acid from the synthetic produced water (ANOVA). The greater the amount of petroleum present, the greater the efficiency. By acidifying the synthetic effluent, the efficiency of removing these naphthenic acids from the synthetic produced water was increased. Response surface methodology (RSM) evaluated these two factors. On the other hand, the initial concentration of cyclohexanecarboxylic acid and petroleum type did not presented great influence on the obtained results, indicating robustness of the process. The methodology carried out with synthetic effluent proved to be efficient in removing the oil and grease content from real effluent (≈ 60% of removal at pH range 2–5).