Degradation pathways of amine-cured epoxy novolac and bisphenol F resins under conditions of high pressures and high temperatures

The ever-rising energy demands are driving the petroleum industry to explore fossil fuels from geologic formations that show conditions of abnormal high pressures and high temperatures, universally known as HPHT conditions [1]. Conditions of HPHT in the downhole oilfield applications are of major concern because of the high demands of the materials involved, and the presence of seawater in the pipeline liquids makes corrosion a pervasive issue across the industry.

Furthermore, the HPHT fields encompassing a gas phase, a hydrocarbon phase, and a seawater phase, combined with high temperature and high-pressure conditions, can result in extensive coating degradation and defects. In general, this extremity of the HPHT zone tends to accelerate the material degradation processes, forcing early and costly replacements.

For this reason, process equipment, wells, tanks, and pipelines in the HPHT zones are often protected with high-performance epoxy-based anti-corrosive coatings. However, the durability and/or degradability of these highly cross-linked coating systems under the HPHT conditions (including the gases such as N2 and CO2, combined with a mixture of hydrocarbon fluids and artificial seawater) are rarely reported in the open literature and the underlying mechanisms remain largely unexplored.

Furthermore, Rapid Gas Decompression (RGD), i.e., when depressurization to ambient conditions takes place during emergency shutdowns, can also lead to failures (e.g., crack initiation and growth in cross-linked networks) caused by the fast release of HPHT phases dissolved in the coating. Consequently, in the present study, the largely unexplored degradation pathways for amine-cured epoxy novolac (EN) and bisphenol F (BPF) epoxy resins at HPHT are investigated under lower limits of HPHT.