Severe tubing corrosion was recently encountered in high pressure sweet oil wells which were thought by all previously established criteria of judgment to be normal, non-corrosive installations. The evidence presented by an ever-increasing number of tubing failures provided sufficient justification for extensive study of the problem. Individual companies began private investigations. In addition, cooperative efforts among engineers of several companies introduced historical data necessary during early phases of investigation. Subsequently, the National Association of Corrosion Engineers’ Corrosion Committee TP-1C undertook the problem as its major project for study. This paper presents the results of statistical studies conducted under the auspices of the NACE committee, as well as basic data established during individual company investigations.
General pitting-type corrosion resulting from carbon dioxide, organic acids and possibly other unidentified corrosive agents occurs frequently in wells producing pipe line oil. The attack continues after wells begin producing water.
Pitting frequency varies with deviations in wall thickness of the tubing. Maximum concentration occurs at points of minimum wall thickness.
Unique and unexplained scale conditions have been observed which obscure the interpretation of tubing caliper surveys. Other popular criteria of corrosion are also difficult of interpretation.
Most known remedial measures have been tried. Inhibitors have proved unsuccessful; galvanizing has been of no value; thermosetting plastic coated tubing, with exceptions, has been promising. Nine percent nickel alloyed steel seems to afford a solution where workover costs are exceptionally high. Nickel plated steel although as yet untried in the field, theoretically seems to offer advantages.
An economic analysis indicates ample justification for further study. It is shown by specific calculation that $1,500,000 must be spent within the next four years because of corrosion in 150 wells concentrated in a small geographic area located in Southeastern Louisiana.
