Upstream oil & gas sector commonly generate oily sludge wastes. This waste can be treated with many methods according to the technical-economic assessment. Recently, co-processing technology usually being chooses in Indonesia. Therefore we need to evaluate co-processing in the legality, technique and economic aspects as the treatment option in Indonesia. The use of co-processing technology as Alternative Fuel and Raw Materials AFR) in cement industry can be implemented into 3 categories, i.e. co-processing of waste, alternative raw materials and mineral components. According to the legality assessment, co-processing comply with Ministry of Environment (MOE) requirements in utilization license because there are three cement industry licensed by MOE, minimal waste heating value 3,000-7,000 kKal/kg (above 2,500 kKal/kg or 4,500 BTU per lb) and controllable emission quality. At the technical aspect, co-processing can be execute easily, fast, practically and total solution (no slag and bottom ash) with no long term liability for the generator. Oily sludge wastes only need to be handling/packing and then transport to the Collector/Profiteer, treatment less than one month for a thousand ton of wastes and wastes actually destroyed without any residue. At the economic aspect, co-processing approximately costs about U$ 80-170 per ton. This cost is more competitive than other methods. Beside that aspects, co-processing give ecological benefits as a waste recovery and decrease the cement industry emission rate. Finally, co-processing is decent to be considered as the main option for oily sludge treatment according this study.