Novel corrosion inhibitors for acidizing oil wells

Acidizing is a common job in both new and old oil and gas wells. In new wells, acids are forced into the pore spaces of the rock formation, dissolving them, enlarging the existing flow channels, and open new ones to the wellbore. In old wells, it is used for the removal of scale deposits which cause plugging the porosity of the formation containing oil and/or gas, and decreasing the production of the wells. Formation of deposits on production equipments is also a major problem, causes corrosion, flow restriction, and production decline. The majority of acidizing treatments utilize HCl at high concentrations and high temperatures. To avoid the acid attack on the metallic surface, highly effective corrosion inhibitors are needed for this process. In this paper, tow inhibitor formulations have been investigated for the inhibition of mild steel in 15 and 20% HCl solutions at 65 and 90 °C. One of these formulations is composed mainly of coal–tar distillation products [CTDP] and the second from the aqueous extract of ginger. The corrosion inhibition effectiveness was measured by the weight loss of the steel coupons after immersing in the acid solution for 6 h. The results showed decrease of corrosion rate [CR] and increase of inhibition efficiency [Inh. Eff.] with increasing the concentration of the two inhibitors. In 15% HCl, the lowest CR values given by CTDP are 1.867 and 22.75 g/m2h, respectively, at 65 and 90 °C. The corresponding blank CR values are 136.03 and 233.667 g/m2h, and the maximum Inh. Eff. values are 98.6 and 90.3%. Ginger extract formulation achieved 99.3 and 96%, respectively at 65 and 95 °C. No significant change in the efficiency of the two formulations has been obtained with increasing the HCl concentration to 20%. The results have been compared with those obtained with currently used commercial inhibitors and it is found that the two formulations are more effective. Two inhibitors formulations have been investigated for the inhibition of mild steel in 15 and 20% HCl solutions at 65 and 90 °C. One of these formulations is composed mainly of coal tar distillation products and the second from the aqueous extract of ginger. The results showed decrease of corrosion rate and increase of the inhibition efficiency with increasing the concentration of the two inhibitors.