Influence of Crude Oil Production Chemicals on the Stability of O/A Emulsions and on Flocculant Efficiency

The water produced during oil extraction contains oil emulsified. Therefore, before being reinjected or discarded, this produced water must comply with the oil in water concentration limits established by Brazil’s environmental regulatory authority, CONAMA. These limits correspond to a monthly average of 29 mg/L and a maximum daily value of 42 mg/L. Treatment of the emulsified fraction, one the most resistant to separation, is commonly carried out flocculation with water-soluble polymers. In this work, synthetic oily waters using heavy oil were prepared, and two types of cationic polymeric flocculants were evaluated, both individually and in combination with a commercial demulsifier and an anionic SPAM polymer, which are commonly used in oil production operations. For this purpose, flocculation tests (jar tests) were performed on oil in water emulsions prepared with different oil concentrations. The results showed that the demulsifier alone reduced the oil removal efficiency of the flocculants. Conversely, the presence of SPAM alone further reduced the performance of the flocculants, at both oil concentrations tested. When used together, these additives almost completely suppressed the action of the flocculants. Particle size analyses confirmed that the most efficient flocculant promoted the formation of larger aggregates, while the presence of the demulsifier and SPAM limited this formation. Interfacial tension measurements showed that the flocculants’ action was directly related to the availability of interfacial area, being impaired when this interface was previously occupied by demulsifier and SPAM.