Internal Casing Corrosion in Sour Oil Wells

A low-cost method of reducing internal casing corrosion in sour oil wells is needed. Results of laboratory weight loss tests suggest that treatment of the inside of the casing with an oil-inhibitor mixture may be a feasible solution. Results of other laboratory tests show that the weight of a paraffin-oil-inhibitor mixture adhering to a steel coupon is several times that of the film deposited from an oil-inhibitor mixture alone. Preliminary results of a field test on two wells showed that rapid injection of several barrels of an oil-inhibitor mixture into the tubing-casing annulus gave complete coverage of the outside of the tubing in the gas space and that the film remained intact for at least six months. It is probable that the inside of the casing in the gas space also was completely covered by the oil-inhibitor mixture.