Abstract: In this study, taking produced water from oil production plant of Chang 2 reservoir, Yanchang Oilfield as a research object, scaling potential of the produced water, as well as the compatibility of produced water with surface water or formation water, were determined by the simulation tool Scalechem. The results showed that mass fraction of BaSO₄ and CaCO₃ scales in produced water would be 176 mg/L and 540 mg/L respectively in surface pipelines, while 168 mg/L of the BaSO₄ and 526 mg/L of the CaCO₃ was predicted to generate in horizontal section downhole, failing to meet the requirements of water reinjection in oil fields. Thus, it was necessary to treat the water with coagulation/flocculation process. The optimum operation parameters were identified to be with PAC dosage at 60 mg/L, CPAM dosage at 1.2 mg/L, the interval time between the above two chemicals was 30 s, and mixing time for flocculation was 5 min. Light transmittance of the treated produced water was 88.1% with better compatibility. According to Scalechem simulation, mass fraction of BaSO₄ scaling was reduced more than 75%, while CaCO₃ scaling was reduced almost 99% in reconciled water after treatment. The proposed treatment was proved to decrease the water production load and satisfy with the water reinjection requirements in oilfield.