Stems as Natural, Green, Non-Toxic Corrosion Inhibitors

Abstract Corrosion during acid treatments causes severe damage to the tubulars and downhole equipment. Consequently, this leads to an increase in expenditure to maintain well production rates and well integrity. NACE estimates the cost of corrosion costs to be roughly 1.372 billion USD annually to the industry, making corrosion control extremely important. Therefore, corrosion inhibitors must be included in any acid treatment formulation. This work aims to develop environmentally friendly and non-toxic corrosion inhibitors that can work in the harsh oilfield conditions. Samples of 10 different stems were tested as sources of potential corrosion inhibitors. To determine the inhibition effectiveness of the different samples, N-80 coupons were exposed to 15 wt% HCl solutions at temperatures between 77-200 °F with 2 wt% of each sample for 6 hours. In addition, a control solution containing no corrosion inhibitor was used to establish a corrosion rate for a base case. At a concentration of 2 wt%, sample 1, 2, and 3 were found to perform the best, exhibiting 94.4% to 99.9% corrosion inhibition efficiency at 77°F. Sample 8 was observed to perform the worst with a corrosion inhibition efficiency of 57.3%. At 150°F, the corrosion rate of sample 1 was found to be 0.0275 lb/ft2, while that of sample 2 was 0.0171 lb/ft2. At this temperature, sample 3 did not perform well, exhibiting a corrosion rate of 0.155 lb/ft2 and thus was not tested at higher temperatures. At 200°F, the addition of a corrosion inhibitor intensifier resulted in a corrosion rate of 0.0136 lb/ft2 for sample 1 and 0.00878 lb/ft2 for sample 2. These results show that a naturally occurring, green, non-toxic corrosion inhibitor can be developed from these stems and can comfortably pass the industry requirement for low carbon steel. Currently used corrosion inhibitors are associated with environmental concerns and severe health risks. Recent developments in corrosion inhibition technology successfully tackled the environmental concerns, but still faces issues with toxicity and performance at high temperatures. The results in this work share two new naturally occurring, green, non-toxic, high-temperature stable corrosion inhibitors that can be developed from stems and can successfully protect the tubular during acid treatments.