Effective Corrosion Mitigation Exploiting Glass Reinforced Epoxy Lined Tubulars in Offshore Producing & Injection Wells

Abstract

Abstract Corrosion in offshore well completions can lead to serious well integrity problems and costly workover operations. Although carbon steel is an ideal material for most completions, under certain conditions corrosion can attack and severely damage carbon steel equipment. Corrosion resistant alloys (CRA) are a good option but come with the considerable downside of very high cost. A relatively simple and cost effective approach to protect completion equipment against these corrosive elements is to line carbon steel completion tubulars with a non-metallic Glass Reinforced Epoxy (GRE). The GRE material properties provide excellent protection against a range of conditions including; highly corrosive fluids, erosive granular materials, Carbon dioxide (CO2), Hydrogen Sulfide (H2S) and acid treatments. The GRE lined Carbon steel is capable of combatting a range of corrosive environments in oil producers, water injectors / supply wells, including water with high concentration of total dissolved solids (TDS), chloride and sulfates and oil with high levels of H2S and CO2. The steel tubing is protected from these unforgiving ecosystems by lining the inside of the tubing with one continuous GRE tube. To secure the GRE lining and to increase the strength, a cement is pumped down the narrow annulus between the GRE lining and tubing internal wall. This procedure is relatively simple with the resultant GRE lined tubing having exactly the same tubing strength properties as the bare tubing. The primary method for detecting any well integrity problems with water injector wells are from determining high pressures in the tubing casing annulus (TCA). To date, all of the water injector wells installed with 7" GRE lined tubing have remained integral with no indication of any corrosion. Several of the oil producer and water supply wells that were lined with GRE have subsequently been worked over to replace faulty equipment; primarily electrical submersible pumps (ESP's). Encouragingly, the condition of the recovered GRE tubing had suffered no corrosion, scaling or other degradation benefiting from the GRE protection. The non-metallic GRE material is exceptionally robust with notable longevity and very resistant to any scale build-ups, leading to improved flow assurance. At the same time being tough enough to withstand any routine well intervention for logging, acid stimulation and other applications. The durable qualities and chemical characteristics of these non-metallic materials in downhole completions is likely to expand in the coming years, with increasing applications being found.