Examinations of effective coagulant for polymer flood produced water and pilot trial in Oman

Polymer flooding is being used as an enhanced oil recovery (EOR) method in Oman. In polymer flooding, injection water of increased viscosity reduces mobility difference between water and oil, thereby improving sweep and oil recovery. The quality of polymer flood produced water (PFPW) is different from produced water (PW) without polymer, and various techniques are being studied for the effective treatment of PFPW. In this paper, the effects of two different coagulants, aluminum sulfate (AS) and polyaluminum chloride (PAC), were examined for the treatment of PFPW. Laboratory tests indicated that the effects of coagulation by PAC were decreased when used for PFPW, compared to PW. This decrease was attributable to interaction of polymer and inorganic carbon, rather than to high pH or high alkalinity alone. On the other hand, laboratory tests indicated that AS would be an effective alternative coagulant for PFPW treatment. Based on these results, a treatment trial with actual PFPW, was conducted with a pilot plant. The pilot trials confirmed that with appropriate level of AS addition and a second coagulation step, PFPW could be effectively treated with AS.