Acid treatments are commonly used in the oilfield to remove inorganic scale or to stimulate formations. Field treatments utilizing acids commonly consist of using hydrochloric acid (HCl), formic acid, acetic acid, or aminopolycarboxylic acids (chelating agents). At elevated temperatures, these acids become highly corrosive and can cause severe damage to tubulars as well as downhole equipment. To minimize tool damage that is generated from the use of these acids, corrosion inhibitors are added to the treatment solution.
Corrosion inhibitors commonly used in the oil and gas industry adsorb to the surface of the metal and forms a barrier. This barrier reduces contact between the metal surface and the corrosive substance, thereby mitigating corrosion damage. However, these corrosion inhibitors are harmful to both the environment and human health. Other new environmentally-friendly corrosion inhibitors are still considered either toxic to the human body or struggle to perform well at high temperature field conditions. To develop new environmentally friendly and non-toxic corrosion inhibitors for high-temperature applications, 19 leaves commonly used as food were tested as alternative sources of corrosion inhibitors.
To determine the inhibition effect of these leaves, N-80 coupons were exposed to 15 wt.% HCl solutions at temperatures between 77-200°F with 2 wt.% of grounded leaves added for 6 hours. Moreover, a solution with no corrosion inhibitor was used to generate a corrosion rate for a base case.
This paper will show the results of such leaves and attempt to provide an awareness of natural leaf extract for use as corrosion inhibitors in conjunction with well acid treatments. Out of the 19 leaves tested, leaf 9 was found to perform the best at 77°F, exhibiting 91.7% corrosion inhibition efficiency. Leaf 18 was observed to perform the worst with a corrosion inhibition efficiency of 11.7% compared to the control case. At 150°F, the corrosion rate of leaf 9 was 0.00206 lb/ft2 which represented a 99.4% inhibition efficiency compared to the control case. At the same conditions, the control solution was found to have a corrosion rate of 0.371 lb/ft2. Leaf 9 was further tested at 200°F with the addition of a corrosion inhibitor intensifier resulting in a corrosion rate of 0.0108 lb/ft2. These results show a new naturally occurring, green, non-toxic, high-temperature applicable corrosion inhibitor that can be developed from edible leaves.