Chemical Demulsification of Oil-in-Water Emulsion from Gas Condensate Field

Abstract

Produced water, also known as oily wastewater, is one of the major wastes in the oil and gas industry. During the hydrocarbon production, formation of emulsion takes place such as oil-in-water emulsion which has a huge financial effect on the sector. Oil and gas industry seeks highly effective and reasonable demulsifying chemicals to separate the oil-in-water emulsions into water and crude oil. Thus, in this publication, resin alkoxylate, cationic polyamine, cationic surfactant and ethylene oxide/propylene oxide (EO/PO) block copolymers are utilized to resolve the oil-in-water emulsion from a gas condensate field. According to the findings of preliminary screening, a unique demulsifier DB was formulated by incorporating resin alkoxylate and cationic surfactant at an optimal weight percentage ratio. Demulsification efficiency (De) of 96 % based on measurement of turbidity was attained after treating the oil-in-water (O/W) emulsion with demulsifier DB at a dosage of 7 ppm.  To determine the demulsifier's efficiency further, the oil-in-water content (OiW) of the produced water was evaluated after the treatment with demulsifier DB. Oil removal efficiency (ORe) of 90% was achieved as the formulated demulsifier DB reduced the oil-in-water content (OiW) of O/W emulsion from 1008.3 ppm to 97.1 ppm within 15 minutes at the dosage of 7 ppm. Furthermore, interfacial tension (IFT) and Turbiscan analysis were performed to further study the demulsification process of blank sample and the addition of the demulsifier DB at the optimized dosage of 7 ppm. At demulsifier DB dosage of 7 ppm, the interfacial tension between oil and water reduced significantly compared to blank sample from 24.98 mN/m to 9.38 mN/m. The produced water sample after treatment with 7 ppm of demulsifier DB resulted in a significant increase of Turbiscan Stability Index (TSI) value of 8 which indicates the rate at which the separation of oil and water occurred. The attained results of IFT and Turbiscan analysis further validate that mixed surfactant system is more efficient than single surfactant system. By combining surfactants with different functional groups, mixed surfactant systems can exhibit greater surface activity than single surfactants.