Paper: Selection, Design, Automation of Corrosion Inhibitor Treatment In Rod Pumped Wells

Experience developed in the Midcontinent Division of Exxon Co., U.S.A. indicates that well corrosion problems in rod pumped wells are directly related to the water cut of produced fluids. In general, severe corrosion problems as measured by excessive rod, pump and tubing failures, are predominant in wells that produce in excess of 30% water. Further, embrittlement and pitting resulting in reduced rod life and fatigue failures are accelerated by the presence of hydrogen sulfide in the produced fluids. Corrosion in rod pumped wells is controlled by maintaining an inhibitor film on all wellbore equipment exposed to produced fluids. The film can be formed and maintained as a well is produced by maintaining an adequate concentration of inhibitor in the produced fluids. The film can also be created by a short contact time with fluids containing a high inhibitor concentration. The film thus formed can be allowed to dissipate using frequent retreatment to maintain protection. Four methods are used to treat rod pumped wells with corrosion inhibitors: squeeze, batch flush. continuous injection, and circulation. The labor and material costs, investment, and treatment effectiveness vary with well characteristics for each method. The purpose of this paper is to present information for selecting the "best" corrosion inhibition technique for a given set of well conditions. "Best" method is defined as the most economical when both well servicing costs and corrosion inhibition expense are considered. This paper also presents formulas and guidelines for design of an effective treatment once the appropriate inhibition technique has been selected. The information presented is grouped in three main sections: (I) Selection of treatment methods; (2) Treatment design; and (3) Application of automatic chemical injectors.