This paper presents a 15-year field case study on the use of glass-reinforced epoxy (GRE)-lined carbon-steel tubing in offshore water-injection wells in the Azeri-Chirag-Deepwater Gunashli (ACG) field in the Caspian Sea. Since April 2008, more than 60 completions have been equipped with GRE-lined, 7.000-in., 29.00-ppf API 5CT-compliant tubing with proprietary metallurgy for sour-service applications and a threaded-and-coupled premium connection, making ACG one of the world’s largest and longest-running offshore GRE deployments.
Field Overview and Application Scope
The ACG field is the largest offshore oil development in the Azerbaijan sector of the Caspian Sea. The ACG covers an area of approximately 432 km2 and comprises seven fixed offshore platforms commissioned between 1997 and 2024, with facilities for production, injection, compression, and processing, all linked by extensive subsea pipeline infrastructure to the onshore Sangachal terminal near Baku.
To maintain reservoir pressure and support recovery, ACG employs both seawater injection (SWI) and produced water reinjection (PWRI). Raw seawater is sourced directly from the Caspian Sea. While moderate in salinity compared with open oceans, the injected fluids remain corrosive because of chloride ions, dissolved oxygen, and biological activity indicated by elevated acetate in produced water. PWRI further introduces additional corrosive constituents, including CO2, trace hydrogen sulfide (H2S), hydrocarbons, and elevated solids loading, creating a service environment capable of reducing the life of unprotected carbon steel tubulars significantly.
The decision to adopt GRE lining for ACG injection wells was influenced by successful deployments in the North Sea and positive qualification test results, coupled with the operator’s strategy to standardize material selection for water-injection service to either GRE‑lined carbon steel or 25Cr corrosion-resistant-alloy (CRA) tubing.
