There have been documented and undocumented corrosion problems in Canada concerning the drilling of oil and gas reservoirs that have H2S content. In the realm of underbalanced drilling, liquid nitrogen has typically been used as the gaseous medium to reduce hydrostatics for underbalanced drilling fluids. Liquid nitrogen does an excellent job of inserting the drill fluid and reducing corrosion potential. Membrane gas, which is generated using membrane fiber technology and air compression/boosting equipment, is an effective means to reducing hydrostatics. This paper will discuss typical corrosion mechanisms and H2S corrosion mechanisms that are a concern in underbalanced drilling based on laboratory experiments. The goal of the paper being to explain trends in corrosion and show the effectiveness of membrane gas for underbalanced drilling applications, with coil tubing.
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