Applicability Evaluation of Demulsification Processes and Optimization of Centrifugal Demulsification Parameters for Highly Emulsified Crude Oil from the Shixi Operation Area

To address the difficulty of demulsifying a water-in-oil (W/O) crude oil emulsion with a high solids content from the Shixi Operating Area, the adaptability of electrostatic dehydration, ultrasonic demulsification, and centrifugal demulsification was compared. A centrifugal demulsification process combined with additives was optimized using response surface methodology and single-factor experiments. The results showed that the emulsion contained substantial amounts of resins, asphaltenes, and inorganic solids, including FeS and carbonates. The small density difference between oil and water further impeded their separation. The maximum demulsification efficiencies of conventional electrostatic dehydration and ultrasonic treatment were only 52.6% and 40%, respectively, and could not meet the treatment requirements. Optimal process conditions were obtained using a Box–Behnken response surface design. Under moderately effective baseline conditions, appropriate dosages of 2.0% sodium silicate and 40 mg·L−1 SP169 were identified. When the optimized process and additives were combined for validation, the mean demulsification efficiency calculated from the volume of separated free water reached 93.5 ± 0.30%. Microscopic observations indicated that the centrifugal force field could disrupt the solid–organic matter emulsified aggregate structure in the system. The optimized centrifugal demulsification process combined with additives showed good adaptability to this type of crude oil emulsion with a high solids content and may provide a reference for demulsification treatment in the field and for similar emulsions.