Thousands of kilometers of pipelines are being utilized to transport produced water among different regions in the Kingdom of Saudi Arabia. Underground pipelines, carrying produced water, are externally subjected to different types of soil. In order to protect them, an external coating and internal cement lining are applied. Produced water had fixed parameters quality range for long periods of time. Decisions were made to increase the concentration of total dissolved solids (TDS) of the produced water from 130 ppm to 300 ppm plus. An increase in TDS of produced water would raise chloride ion concentration.
The current research aims to measure the effects of higher content of chloride in produced water on water pipelines. Onsite visual inspection of pipeline internals was performed after 1 year of exposure to new TDS range. In addition to that, corrosion behavior of carbon steel and two types of stainless steel in different chloride concentrations and temperatures were studied through weight loss and electrochemical methods.
Results showed that carbon steel experienced the highest corrosion rates at higher temperatures. Changing the content of chloride had small effects on corrosion rate at the same temperature. Stainless steels were resistant enough to both chloride concentration differences and varying temperatures.
Saline Water Conversion Corporation (SWCC) is the largest producer of water by its different water desalination plants distributed around the kingdom. Produced water is transmitted through underground pipelines. These pipelines are more than 8,000 KM in length and varying diameter from 8 thru 75 in. These pipelines are internally protected by cement mortar lining and externally by polyethylene coating. Produced water quality is specified within fixed ranges of parameters for long periods of time as indicated in Table.1. In compliance with the new raised standards, TDS would be increased. This TDS increase in transmitted produced water would be accompanied with an increase in chloride ion concentration. This research was conducted to study the effect of increasing temperature and chloride concentration in terms of corrosion aspects. From corrosion point of view, the electrochemical reactions (ER) are negligible in the presence of an optimum cement lining layer of underground pipelines, since it would impede these reactions resulting in corrosion prevention. However, if there is cement delamination, then two possible forms of corrosion can take place either uniform attack on the carbon steel pipe area where cement layer is absent or localized attack where some portions of the material are not covered with cement in the same area. Studies were accomplished through two different techniques: weight loss method (WLM) and electrochemical technique. WLM was carried out to evaluate corrosion rates. Electrochemical technique was conducted by three different testing methods: Open Circuit Potential (OCP), Electrochemical Impedance Spectroscopy (EIS) and Potentiodynamic Polarization (PDP) to measure corrosion tendencies and detect any localized corrosion. In both techniques, test coupons were of three different materials: Carbon Steel API 5L X52, Stainless Steels UNS S30400 and UNS S31603, which would be referred to later as follows: X-52, 304 SS and 316 SS, respectively. These coupons were prepared and tested in different chloride concentrations solutions at three different temperatures. Produced water was modified to have the following concentrations of chloride ions (25, 50, 83 & 100) ppm, to be used as an immersion environment in both tests. Testing temperatures were varied to consider temperatures of transmitted water in winter and summer seasons (25 °C, 40 °C & 50 °C).
