A special type of reactor with a high active surface-to-volume ratio was used for investigation of organic pollutants degradation from a gasfield produced water by photoelectrocatalysis process. The GC–MS analysis showed that there were more than 50 organic substances in this wastewater; therefore, COD was considered as the target parameter for studying. A simple evaporation process used for decreasing high TDS of the wastewater reduced its electrical conductivity from 6300μS/cm to 1100μS/cm and also initial COD decreased simultaneously from 9500mg/L to 750mg/L. Distilled wastewater from the evaporation process was treated again by the photoelectrocatalysis process using a coil type microreactor, and its COD dropped off to 143mg/L. Instead of usual semiconductors in photoelectrocatalysis like TiO2, boron carbon nitride (BCN) nanosheets are used as a photocatalyst in this study. Investigating the impact of different parameters on COD removal efficiency showed that the greatest COD removal efficiency (81%) was obtained at residence time 15min, pH=3, applied cell voltage 20V, electrical conductivity=2500μS/cm and H2O2 concentration of 8mM.