Synthesis and performance evaluation of a polyacrylate flotation agent for treatment of produced water from deepwater oil and gas fields

Improving flotation treatment of produced water from deepwater oil and gas fields requires agents that remain effective in the presence of hydrate inhibitors. Here, we synthesized and screened polyacrylate flotation agents prepared from acrylate and cationic monomers. Oil removal efficiency was used to select the synthesis conditions. The acrylate mixture comprised tetrahydrofuran acrylate (THFA) and acrylic block polyether ester (A1000), and the cationic monomer was N-(3-dimethylaminopropyl)methacrylamide (DPM). The selected DPM-to-(THFA + A1000) mass ratio was 1:4, the total monomer concentration was 25 wt%, the VA-044 initiator concentration was 0.5 wt% of the total monomer mass, and the reaction was conducted at 50°C for 6 h. The resulting product was designated PDT. For model produced water containing 100–1000 mg/L condensate oil and 1000–10000 mg/L monoethylene glycol (MEG), oil removal efficiency exceeded 90% at PDT dosages of at least 10 mg/L, nitrogen flow rates of at least 300 mL/min, and flotation times of at least 180 s. Interfacial elastic modulus and oil-coated-bubble measurements support an interpretation in which PDT promotes oil-droplet coalescence and shortens the drainage and spreading stages of droplet-bubble attachment. These effects may improve collision and adhesion efficiencies under the tested conditions.