Seed Extracts as Natural, Green, Non-Toxic Corrosion Inhibitors

Abstract

Acid treatments are commonly used in the oilfield to remove inorganic scale or to stimulate formatio ns. These treatments typically consist of using hydrochloric acid (HCl), acetic acid, formic acid, or chelating agents. At elevated temperatures, these acids are highly corrosive and can cause severe damage to tubulars as well as downhole equipment. To reduce damage from these acids, corrosion inhibitors are added to the treatment solution. Corrosion inhibitors used in the oil and gas industry are typically quaternary amines or sulfur-containing compounds. These compounds adsorb to the surface of the metal, thereby reducing contact between the metal surface and the corrosive substance. However, these corrosion inhibitors are damaging to the environment and harmful to human health. Alternative new environmentally-friendly corrosion inhibitors are also either toxic to the human body or face performance limitations at higher temperature field applications. To develop new environmentally friendly and non-toxic corrosion inhibitors for high-temperature applications, 15 edible seeds were tested as alternative sources of corrosion inhibitors. In order to determine the inhibition effect of 15 different seeds, N-80 and S13Cr coupons were exposed to 15 wt.% HCl solutions at temperatures between 77-250°F with 2 wt.% of grounded seed added for 6 hours. In addition, a control solution containing no corrosion inhibitor was used to establish a corrosion rate for a base case. This paper will show the results of such seeds and attempt to provide an awareness of natural seeds extract for use as corrosion inhibitors in conjunction with well acid treatments. It was noted that out of the 15 seeds, seeds 1 and 2 were found to perform the best at these conditions, exhibiting more than 90% corrosion inhibition efficiency. Seed 4 was observed to perform the worst, exhibiting only 16.8% inhibition efficiency. At 150°F, 2 wt.% of seeds 1 and 2 were tested with seed 1 achieving a corrosion rate of 0.00253 lb/ft2 while seed 2 was unable to provide sufficient inhibition with a corrosion rate of 0.153 lb/ft2. The control solution was found to have a corrosion rate of 0.371 lb/ft2 over the 6 hours at 150°F. Seed 1 was further tested at 200°F with the addition of corrosion inhibitor intensifiers and resulted in a corrosion rate of 0.00087 lb/ft2, while at 250°F, a corrosion rate of 0.00811 lb/ft2 was observed. The tests using S13Cr also showed that seed 1 worked well as a corrosion inhibitor for CRAs. The thermal degradation of seed 1 was also examined using NMR. These results show a new naturally occurring, green, non-toxic, high-temperature applicable corrosion inhibitor that can be developed from edible seeds.