(181h) Effects of HPHT Conditions on the Rate of Degradation of High Performance Epoxy Coatings

Fossil reservoirs have already been exploited for many years and they are fast approaching depletion. Rapid depletion of oil reservoirs being imminent, the oil and gas industry is gradually shifting focus towards High Pressure and High Temperature (HPHT) wells and reservoirs for extraction of crude oil and natural gas. Unlike ordinary wells, extremely high pressures and high temperatures along with highly corrosive components constitutes the prerequisite for HPHT wells. Corrosion of any designed component in such hostile environments is an issue of major concern and face massive challenge to withstand and maintain its structural integrity. The most prevalent method to prevent corrosion of components and substrates under HPHT conditions is to coat the inside (and outside) walls with high cross-linking and anti-corrosive epoxy coating systems.

Attributing to its relatively high molecular weight, high corrosion resistance, outstanding adhesion properties, mechanical properties, it’s easy and widely known fabrication process and its operation in HPHT conditions, the present examination investigates the corrosion degradation kinetics of amine cured phenolic Novolac epoxy (A) and Bisphenol F epoxy (B) coating system. The current study analyses the effect of HPHT conditions that primarily constitutes of sea water as the liquid phase, p-xylene as the hydrocarbon phase, high pressure conditions generated by using nitrogen (N₂), carbon dioxide (CO₂) and hydrogen sulphide (H₂S) as gas phase at elevated temperatures on A and B coating systems. The present study deals with failure pathways, degradation mechanisms, defect initiation and propagation thereby establishing a correlation to epoxy coating physical and chemical principals.

The research findings indicate the interaction of each of the phases and components, individually as well as synergistically on degradation rate of epoxy coatings. A mechanistic pathway has been derived for the time dependent chemical changes occurring in both coating systems A and B. Further effect of post curing of epoxy coating systems reflecting higher corrosion resistance in both coating systems A and B has been studied independently. The synergistic effects under HPHT conditions on coating systems A and B are described in terms of physical defects formed and chemical changes occurring as part of time related degradation during the exposure time. Along with basic coatings characterization techniques, the present study has involved a new non-destructive method namely Scanning Acoustic Microscopy (SAM) through which the defect initiation becomes evident and establishes a time related defect propagation towards the substrate of the coating system. Defects such as blister formation, cracks, voids and delamination could be examined distinctly along the cross section without damaging the coating.

This endeavoring HPHT research is one of a kind and reflects that three basic concepts – Interaction of different HPHT components and phases amongst themselves, interaction of HPHT conditions with epoxy coating systems, and establishment of its physical and chemical degradation pathways – emerge as potential foundations that may allow us to understand the much desirable life prediction studies of epoxy coating systems under HPHT conditions. With looming concerns of more aggressive conditions of HPHT reservoirs and wells in future, this research helps in understanding the degradation pathways, accumulates time related data and opens a wide spectrum to develop enhanced formulations to withstand the forthcoming HPHT pre-requisites.