Corrosion Control in Gas Lift Wells★

Abstract

Abstract Conditions in gas lift wells producing appreciable proportions of water are reviewed. Principal corrodent is reported to be carbon dioxide and certain peculiarities of gas lift wells are enumerated. Because of the importance of the ionic composition and chemical content of produced waters, especially those of Gulf Coast wells, the scaling problem associated with these wells is an important consideration in devising inhibitive practices. Because a current statistical analysis indicates about 4000 Gulf Coast gas lift wells probably are already corrosive and because it is expected that 16,000 ultimately will be corrosive the authors point out a potential corrosion damage of as much as $16,000,000 annually. Chemicals used to inhibit corrosion in these wells must have the faculty of penetrating the column of oil and water standing in the well. Laboratory experiments using a model gas lift well and actual produced fluids are described. Some currently available inhibitors have the disadvantage of forming insoluble salts with the calcium and magnesium ions and thus their use is precluded. Furthermore these compounds have not proved stable at reservoir temperatures. Arsenical inhibitors consisting of solutions of sodium arsenite and sodium polyphosphate which proved in tests to be an adequate inhibitor, subsequently were the cause of such difficulties, their use was abandoned generally. Continued tests in two wells indicated they could be used when properly diluted if treatment was continuous and batch fed. Arsenic precipitation was seen as a possible bad effect but reversion of polyphosphates was not encountered. Further there was some suspicion arsenic from these inhibitors resulted in the poisoning of the catalyst in a catalytic cracker. Subsequently it was learned the standard electrical desalting process effectively removes the arsenic. Investigations of organic polar compounds weighted with ethylene glycol resulted in the Continental Oil Company developing its own inhibitors. One of these is being tested in a 7600-foot well.