The rate of produced water production of oilfields increases as oilfields age. This study aims to evaluate water quality of produced water from oilfields in the Heglig area using various water quality evaluation indices and study the significance of evaporation for cumulative pollutants after bioremediation in Heglig oilfield. Produced water samples were collected and analyzed for three locations in Heglig and Neem oilfields in order to determine the physicochemical, radioactivity, and heavy metal variables. The data obtained were used to determine the heavy metal pollution index, heavy metal evaluation index, weighted arithmetic water quality index, and Canadian water quality index (CCME WQI). The study revealed very poor water quality and high heavy metals at Neem oilfield. In addition, produced water quality at Heglig oilfield before the bioremediation was very poor and after the bioremediation was found to be poor, also the heavy metals were low before the bioremediation and medium after the bioremediation. Low levels of chemical oxygen demand (COD) oil in water, and total suspended solids (TSS) are mainly responsible for improvement of water quality after the bioremediation. Variation in the heavy metals before and after the bioremediation was a result of cumulative effect in the evaporation ponds.