Investigation and Prediction of Corrosion and Scaling Tendency in Wastewater Pipelines and Tubings of Disposal Wells of Rag-e-safid Crude-Oil Desalting Unit

The corrosion and scaling impose billions of dollars on the oil industry annually. Corrosion  is one of the main reasons for the loss of metals in oil wells and production processes. Moreover, corrosion causes that the costs of maintaining wellhead and downhole equipment and its replacements and repairs increase. In addition, the cost of production increases due to corrosion. The purpose of this study is the determination of the corrosion rate and scaling deposition of wastewater of Rag-Safid desalination unit and tubing of the disposal well of this field using corrosion and scaling indexes until appropriate solutions for removal and minimization of corrosion and scaling in wastewater transmission tubes and disposal wells are provided. In this research, 10 indexes including Langelier, Ryznar, Puckorius, Aggressiveness index, Larsen index and Larson-Scold index, driving force index, Momentary excess index, saturation index, scaling index, Stiff and Davis saturation index (S and DSI), and the rate of corrosion rate (CRu) in terms of millimeters per year (mm/year) were measured by sampling parameters of wastewater of Rag-Safid desalting and formation water of this field and used for predicting scaling and corrosion rates. After considering the results of 10 corrosion indexes, scaling, and the rate of uniform corrosion (CRu), it is found out that the rate of corrosion of produced wastewater is high (in this study, the rate of CRu is equal to 67.5 mm/year). In addition, carbonate calcium has precipitated at the wellhead and in transmission pipes of disposal well due to the existence of calcium (equal to 3926 mg/L) in the wastewater. Finally, Rag-Safid desalination unit forms due to the existence of (1) low amount of barium (equal to 5.625 mg/L) in the produced wastewater and (2) precipitated carbonate calcium (equal to 3926 mg/L).