Long term chemical and physical performance of aliphatic amine cured fiberglass Tubulars in high pressure super critical application of CO2 in both cyclic and static conditions have been investigated. No physical or chemical degradation was detected at the selected test condition of 2300 PSI and 120 F of carbon dioxide in cyclic or static conditions. Further analysis suggests a slow rate of CO2 penetration into the amine cured epoxy laminate. The failure mechanism model developed and presented here suggest a predictable failure based on stress due to pressure and temperature. The verification of the model presented paves the way for major simplification and cost reduction potentials in future construction and extension of a CO2 WAG Piping Systems, by combining CO2 and water injection lines into one.
Carbon Dioxide (CO2) injection is being used commercially to produce oil that normally would be unrecoverable. CO2 is injected in the super critical state at a surface pressure of about 1500 to 2500 PSI. "CO2 is an efficient injectant because it dissolves readily in both oil and water, with CO2 solubility increasing with increasing pressure. The dissolution of CO2 in oil increases or swells the crude volume and decreases the crude viscosity, which results in a more mobile oil bank and improved sweep efficiency." (Reference 1).
Generally, in order to prevent channeling and maximize flood profitability, implementation of water alternating gas (WAG) injection becomes necessary. The CO2 WAG systems increases corrosion concerns drastically due to formation of carbonic acid and the contamination of produced water used for re-injection for metallic tubulars.
With a proper selection of raw materials, outstanding results have been achieved in the past 25 years using fiberglass tubulars in low pressure or low concentration applications of CO2 to combat corrosion problems. However, a few initial set backs in the early 80's, due to improper raw material selections, connection integrity, misapplication, or pure mishandling of the product, kept the usage of FRP Tubulars to a few selected projects for high pressure CO2 WAG Systems. The information presented here is intended to provide a reliable and predictable failure mechanism to facilitate selection and operation limitation of FRP Tubulars for a trouble free corrosion controlled high pressure CO2 WAG Piping System.
From a chemical resistance stand point, selection of raw materials, especially the solvent resistance and cross link density of the matrix materials, have a direct impact on the functionality of fiberglass tubulars in super critical applications of CO2.
The three raw materials employed in manufacturing of fiberglass tubulars are epoxy, glass and a curing agent. The epoxy contributes mainly to the strength, temperature and chemical resistance of the finished products. The glass provides high strength and load carrying capabilities. The curing agent cross links and converts the epoxy to a solid, which in turn protects and encapsulates the glass from chemical attack. It also plays a major role in chemical and heat resistance of the systems.