Abstract
Separation of oil from produced water is a major issue common to oil-producing countries. During this study, salts (NaCl, NaNO3, MgCl2, CaCl2) were added to simulated produced water (containing emulsified oil) to see the effects of such addition on oil separation. Results indicated that oil-water separation was enhanced as emulsified oil floated to the surface where it could easily be collected. Oil recovery ratio increased with increasing salt concentration, with a maximum oil recovery ratio of 96.3%). The recovery ratio stopped increasing beyond certain salt concentrations. Addition of salts which include divalent cations such as Mg2+ and Ca2+ indicated high oil recovery at lower salt concentrations than that of monovalent cations such as Na+.
After oil recovery by salting-out with NaCl, coagulation treatment was conducted for high salinity produced water to remove remaining oil. Results showed that there was minimal differentiation for optimum PAC addition under several salt concentrations (1~20% NaCl). Addition of MgCl2 and CaCl2 at 5% concentration, indicated effective treatment, similar to that of NaCl.
Addition of NaCl to solution containing polymer for enhanced oil recovery, drastically decreased its viscosity. This result indicated that the addition of salt to polymer flood produced water lowers its viscosity, resulting in easier coagulation treatment.
In order to reduce treatment cost, concentrated brine from reverse osmosis (RO) desalination of saline water (with salt concentrations up to sea water level), could be used instead of aforementioned salts.
