Corrosion Behavior of CRA’s in High Density Packer Fluids at High Temperature

Abstract Results from an experimental investigation carried out in high density brine packer fluids are presented. Different variables were examined, namely temperature, time of exposure, chemical inhibition and brine composition and density. Tests to compare the performance of different classes of stainless steels were carried out by autoclave exposure under different deareated brines solutions: NaCl/NaBr, CaCl2/CaBr2 and CaBr2/ZnBr2; CaCl2, CaCl2/CaBr2/ZnBr2. General corrosion, localized corrosion (pitting and crevice), galvanic corrosion and resistance to environmental cracking were evaluated both in absence of corrosion inhibitor and with the addition of two different commercial inhibitors. Duplex steels were very resistant to the localized corrosion, although pitting and crevice were present in some combination of brine and temperature. The martensitic steel was very sensitive to the general and the localized corrosion. Brine CaCl2/CaBr2 ρ = 1.75 g/cm3, showed at 200 °C, a pitting on 13%Cr lower than expected. This is probably due to the general corrosion which show a mechanism competitive with localized corrosion. As a result, pitting corrosion is a matter of big concern when applications in heavy brine are considered. In fact only the most alloyed materials at temperature below 200°C can be considered as immune. As a consequence, the effect of commercially available corrosion inhibitors is sometime lower than expected and there is a need of further improvements of corrosion inhibitors for the application to the CRA’s (Corrosion Resistant Alloys) in brine environments at 200°C.