Diesel tail gas drilling belongs to gas-based underbalanced drilling technology owning the advantages of protecting oil/gas reservoir and improving rate of penetration. Due to complex composition, especially containing carbon dioxide, oxygen, and erodible solid particles, diesel tail gas can give rise severe corrosion to drilling pipes and air compressor valve plates. The corrosion effect of temperature, total pressure and flow velocity on S135 drilling pipe steel and 13 chrome stainless steel were investigated simulating corrosion environment of diesel tail gas. The image and composition of the corrosion product were analyzed by the surface analysis means as scanning electron microscope, X-ray diffraction and so on. The results indicate corrosion rate of dynamic liquid phase exceeds that of dynamic gas phase, S135 steels corroded more badly than 13 chrome stainless steel, at the first the corrosion rate increasing and then decreasing while enhancing temperature, and improving with total pressure or flow velocity rise. Field experience and laboratory test indicate that hereinafter measures should be adopted to protect drilling tools and compressor valve plates from corrosion failure such as improving material quality, modifying tools structure, perfecting environment, also strengthening management and maintenance.

Underbalanced drilling technology on diesel tail gas is used successfully in Well Xing 24. The diesel tail gas drilling is unsuitable for watered gas well and high pressure gas well.

This paper is the first in a series of studies designed to investigate corrosion of diesel tail gas. The goal is to better understand the advantages and disadvantages of diesel tail gas drilling technology, to be able to select the proper corrosion control and extend diesel tail gas underbalanced drilling in suit region.

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