EVALUATION OF CHEMICAL TREATMENTS IN NATURAL GAS SYSTEMS VS. MIC AND OTHER FORMS OF INTERNAL CORROSION USING CARBON STEEL COUPONS

摘要

Monitoring of internal corrosion by some oil and gas operators has included analysis of gas, liquid, and solid samples in combination with corrosion detection devices such as weight-loss coupons and electronic probes. Although these devices typically detect when significant uniform corrosion is occurring, they are often limited in their abilities in detecting localized attack whose initiation and development may be subtle. Also, correlations of gas/liquid compositions with corrosion measurements are sometimes difficult. Even when localized corrosion is able to be discerned, identification of the primary initiation mechanism is often overlooked. Since understanding the basis of the corrosion attack is important when implementing mitigation measures, it became apparent that an applicable method that gave such insight was crucial in administering an effective internal corrosion control program. Therefore, specially prepared coupons that allowed a combination of analytical techniques to be performed were developed for use in actual operating systems to detect microscopic pit initiation, including those determined to be due to microorganisms. Such coupons have been used successfully at hundreds of different monitoring sites in a variety of natural gas operating systems for twelve years with notable decreases in internal corrosion leaks and chemical expenditures.