Enabling Carbon Steel with a Special Dense CO₂ Corrosion Inhibitor – A Field Study

The asset integrity of a dense phase, super critical CO₂ (scCO₂) production system is critical to efficient, safe, cost effective operation. Until recently these assets were managed using carbon steel lined with a thick, presumably resilient polymer. However, these polymer lined pipes pose a significant problem in terms of cracking. Corrosion behind the liner was causing a hydrogen cracking issue that was difficult to mitigate. Introduction of a specially designed scCO₂ corrosion inhibitor has shown that bare carbon steel can be protected against corrosion in these harsh conditions. This new method of asset management enables more efficient, less costly, and safer operation for the operator. This paper shows data from a field trial strongly supporting the advantageous use of this new technology.

In recent years the oil and gas industry has made significant commitments to carbon reduction.¹ Aligned with the goal of decreasing carbon emissions the authors have developed a corrosion inhibitor (CI-1) that is intended to protect scCO₂ systems that are wet or water contaminated (1000 ppm).² The development and composition of this corrosion inhibitor (CI) for dry scCO₂ is reported elsewhere.^2,3 While chemical companies have been treating high water cut, production enhanced, CO₂ floods (i.e. enhanced oil recovery [EOR]) for several decades there were no inhibitors designed specifically for CO₂ disposal systems or wet scCO₂ systems producing CO₂ for sale.⁴

During the development of CI-1 several key criteria were specified for a CI applied in a mostly dry system expected to have ∼ 1000 ppm water. Namely this CI needed to be highly soluble in scCO₂ so it could be injected into the dry gas and be transported to areas of the system where water might accumulate. If the inhibitor was insoluble in scCO₂, it could precipitate near the injection point and cause gunking. Through the development of CI-1 it was determined that many CIs commonly used for EOR were insoluble in scCO₂ and therefore unable to transport seamlessly to the point of need. CI-1 was found to meet this criterion. In addition it was determined that commonly used amines which work in natural gas applications were susceptible to salt formation in scCO₂ systems if the pressure was to drop into gaseous conditions.