Abstract
Oil and gas production from highly saline reservoirs can necessitate the injection of water (wash water) to dilute the formation water and prevent halite precipitation and reduced flow through the production system. This operation may represent a potential threat due to the dissolved oxygen in the wash water, which can be exacerbated by H2S from the reservoir and/or lift gas. The present paper investigates the threats associated with the co-mingled wash water, formation fluids and lift gas with respect to common completion materials. Several scenarios were investigated:
Routine production (produced water has moderate chloride concentration and very low dissolved oxygen)
An interruption in the supply of wash water (i.e. produced water comprises high chloride formation water alone)
An interruption in the supply of wash water, followed by wash water with high O2 concentration supply (halite precipitation on the completion materials, followed by exposure to produced water comprising higher content of dissolved oxygen i.e. out-of-specification wash water)
Among these, the latest is the worst-case scenario that could occur (in the absence of specific procedures and equipment trips that would otherwise prevent it). Stress Corrosion Cracking (SCC) and general and localized corrosion resistance of UNSa N07718, UNS N08535 and UNS S39274 were evaluated through a laboratory testing program.
