Experimental evaluation of henna extract as a corrosion inhibitor additive in sandstone acidizing and its side effect on rock/fluid system

Green inhibitors are promising alternatives to toxic corrosion inhibitors. Recently, several researches are conducted to investigate the anti-corrosive property of henna extract in different media. The current work investigates for the first time the inhibitive characteristic of the henna in protecting the N80 API steel immersed in the regular mud acid in the range of 28-75 degrees C, beside its side effect on reservoir rock and fluid during acid stimulation. Potentiodynamic-polarization, electrochemical impedance spectroscopy, and immersion tests were employed for corrosion studies. The compatibility of the inhibitor with reservoir rock and reservoir fluid was investigated through the wettability test conducted via the sessile dope technique and the sludge test applied by the Houchin method, respectively. The results confirm the efficiency of the inhibitor in protecting the N80 steel in regular mud acid in the range of 28-75 degrees C. The optimum concentration of henna at 28, 40, 60, and 75 degrees C was 1.6, 1.4, 0.8, and 0.4 ppm, respectively. The consequent inhibition efficiency for all temperatures is more than 80% and increases with the temperature rising. The thermodynamic analysis confirms the chemical adsorption of henna molecules on the metal face through a spontaneous endothermic reaction. This inhibitor causes 0.96 wt% additional sludge precipitation in contact with regular mud acid, which is the minimum value in comparison with the main acid and other acidizing additives selected from a commercial package. The contact angle of n-heptane on rock samples aged with synthetic brine, dead acid, and inhibited dead acid was 41, 48, and 54 degrees, respectively. Results illustrated that henna extract tends the samples toward the oil-wet phase. Overall, the results of this comprehensive study could secure the industrial use of this additive in sandstone acidizing.

Automated summary

This study investigates the inhibitive characteristic of henna extract as a green corrosion inhibitor in protecting N80 API steel immersed in regular mud acid. The results confirm the efficiency of henna in protecting the steel in the specified range of temperatures, with the optimum concentrations varying at different temperatures. The study also explores the compatibility of the inhibitor with reservoir rock and fluid, demonstrating promising results for industrial use in sandstone acidizing.