Chlorine Dioxide and Corrosion in the Oil and Gas Industry

Chlorine dioxide (ClO2) is widely recognized for its effectiveness as a biocide in the oil and gas industry, particularly in hydraulic fracturing and water treatment processes. However, its impact on corrosion, especially on carbon steel used in these operations, has been a subject of considerable debate and investigation. Significant research has shown, however, that chlorine dioxide stands up well in this category among other biocides.

Throughout this article, there are several mentions of studies and/or research. The research referenced comes from two papers by Greg Simpson, Ph.D. SPE. The Corrosion of Carbon Steel by ClO2 and Impact of Produced Water Salinity on the Corrosion by Chlorine Dioxide and its Inhibition are the two papers that are used to form these findings.

ClO2 as a Biocide and Corrosion Mitigator

ClO2 is valued for its ability to control bacteria and biofilms, which are significant contributors to corrosion in oilfield operations. Traditional biocides, such as aldehyde-type and thiocarbamate biocides, often fail to adequately control bacterial populations and biofilms, leading to persistent corrosion issues. Historical reports have demonstrated that the introduction of ClO2 can dramatically reduce bacterial counts and sulfide concentrations, leading to a corresponding decrease in corrosion rates. For example, in a waterflood operation near Wilmington, California, the use of ClO2 reduced corrosion rates from 30 mils per year (MPY) to 0.8 MPY within a year.

Corrosive Effects of ClO2

While ClO2 is effective in mitigating microbial-induced corrosion, its oxidizing nature means it can still contribute to corrosion, particularly in the absence of corrosion inhibitors. Studies have shown varying degrees of corrosion depending on the concentration of ClO2 and the method of its generation. For instance, a study found that the corrosion rates increased with the concentration of ClO2 up to about 15 mg/L, beyond which the rates plateaued. This suggests that while ClO2 is corrosive just like any biocide, its impact is significantly less than that of untreated microbial and sulfide-laden water.

Generation Methods and Corrosion

The method of ClO2 generation plays a crucial role in its corrosivity. Four different methods were evaluated: electrolytic ClO2 generation, chlorine gas reaction with sodium chlorite, a NaClO3/H2O2 precursor mix, and a dry mix product. The study found that the first three methods produced ClO2 with minimal byproducts and resulted in lower corrosion rates. However, the dry mix product, which included significant amounts of chloride and sulfate ions, led to higher corrosion rates. This indicates that impurities in ClO2 solutions can exacerbate corrosion, therefore, the need for professional services to properly generate chlorine dioxide is paramount.

Influence of Water Salinity

Produced water salinity significantly affects the corrosion rates of carbon steel when treated with ClO2. Higher salinity levels generally correlate with lower baseline corrosion rates, but the addition of ClO2 increases corrosion rates more substantially at lower salinities. For example, at a salinity of 2.3%, ClO2 addition increased the corrosion rate by about 21-26 MPY. In contrast, at higher salinities (e.g., 9.3%), the increase was less pronounced. This highlights the importance of considering water chemistry when applying ClO2 in field operations.

Corrosion Inhibition Strategies

To mitigate the corrosive effects of ClO2, the use of corrosion inhibitors is essential. Several inhibitors have been tested, with varying success. For instance, both single inhibitors and blended inhibitors have shown promising results in reducing ClO2-induced corrosion in produced water during tests. These findings suggest that effective corrosion inhibition can allow the continued use of ClO2 as a biocide without significantly compromising the integrity of oilfield equipment.

ClO2 remains a valuable tool for microbial control in the oil and gas industry, particularly in hydraulic fracturing and produced water treatment. While it is inherently corrosive, the extent of its corrosive impact can be managed through careful consideration of its generation method, water salinity, and the use of appropriate corrosion inhibitors. Continued research and field studies are essential to optimize the application of ClO2, ensuring both microbial control and equipment longevity. If you would like to learn more about chlorine dioxide’s corrosivity in or how it is utilized in the oil and gas industry, please fill out the contact form below and a PureLine representative will be in contact with you!