| Summary: | An experimental investigation has been carried out to determine the rheological and corrosive properties of Al-Ghatt clay, when used as a basic constituent for drilling fluid, on mild steel and J-55 steel alloys normally used in oil and gas wells casing fabrication. The study was extended to investigate the effect of a sodium hydroxide (NaOH) addition on the corrosive properties. Corrosion rates were measured under both static and dynamic conditions at 15% by weight clay concentration and with the addition of various concentrations of sodium hydroxide (NaOH). Under the static conditions, the maximum corrosion rate was found to vary from zero to 73.25 mil-inch/year. Under dynamic conditions, however, a maximum corrosion rate of 155.3 mil-inch/ year and a minimum of 0.125 mil-inch/year was detected. The results showed that the resistance to corrosion of the steel alloys is very good at high alkalinity drilling fluids in both static and dynamic conditions. Based on the rheological and corrosivity tests, drilling fluids formulated from Al-Ghatt clay are suitable for oil and gas wells drilling as long as the concentration of the NaOH is maintained at 1% by weight.
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