Title : Managing carbon steel flowline integrity under high co2, elevated temperature, and water cut conditions
Abstract:
Carbon steel flowlines remain one of the most widely used transportation systems in the oil and gas industry due to their mechanical strength and cost-effectiveness. However, as oilfields mature, increasing water production, higher operating temperatures, and elevated carbon dioxide (CO₂) concentrations significantly accelerate internal corrosion, resulting in frequent flowline leaks, production interruptions, and increased maintenance costs.
One of the primary drivers of corrosion is the continuous increase in water cut, which enlarges the electrolyte phase inside the pipeline and promotes electrochemical corrosion. This challenge becomes more severe with the expansion of gas lift operations, where the increasing number of gas lift wells often raises produced fluid temperatures, accelerating corrosion kinetics and increasing the degradation rate of carbon steel. In addition, dissolved CO₂ forms carbonic acid in the presence of water, creating a highly corrosive environment capable of causing localized attack, pitting corrosion, and rapid wall-thickness reduction.
Another significant but frequently underestimated factor is pipeline topography. Low-elevation sections (low points) naturally collect produced water due to gravity, creating stagnant liquid zones where corrosive species remain in continuous contact with the pipe wall. These locations commonly become corrosion hot spots and are frequently associated with leak incidents.
This paper discusses practical integrity management strategies for reducing carbon steel flowline failures under these combined operating conditions. The first strategy involves replacing conventional carbon steel with non-metallic pipeline technologies, including Reinforced Thermoplastic Pipe (RTP), Glass Reinforced Epoxy (GRE),
High-Density Polyethylene (HDPE), and other advanced composite piping systems, which eliminate internal corrosion while reducing maintenance requirements. Where technically applicable, Cathodic Protection (CP) systems provide additional mitigation against external corrosion, particularly for buried flowlines. Operational mitigation methods include Intelligent Pigging Survey (IPS) for early defect identification and dewatering pigging programs to remove accumulated liquids from low points.
Furthermore, continuous corrosion inhibitor injection is presented as an essential barrier for controlling CO₂ corrosion, while suitable internal and external coating systems provide additional protection for extending pipeline service life.
The paper concludes that sustainable mitigation of flowline leaks requires an integrated integrity management approach that combines appropriate material selection, cathodic protection, proactive inspection, operational optimization, pigging, chemical treatment, and protective coating systems. Implementing these measures significantly improves asset reliability, reduces leak frequency, enhances operational safety, and lowers long-term lifecycle costs.
