The corrosion characteristics were studied of dense salt solutions used as packer fluids. Among the salts considered were (1) NaNO3, (2) CaCl2, (3) Ca(NO3)2, (4) ZnCl2, (5) NaNO3-CaCl2, (6). Ca(NO3)2-CaCl2, and (7) CaCl2-ZnCl2. Only slight corrosivities were noted for the first three solutions. However, stress corrosion cracking was encountered in NaNO3 solutions and in some mixtures of NaNO3 and CaCl2. Zinc chloride was too corrosive to obtain useful densities by itself.

Both NaNO3-CaCl2 and Ca(NO3)2-CaCl2 exhibited severe pitting at elevated temperatures. This attack was observed to some degree on a variety of oil country materials. Penetration rates on the 1020 coupons were in excess of ¼ inch per year. The pits were very localized; polish marks were present immediately adjacent to a complete penetration.

A study of CaCl2-ZnCl2-H2O mixtures yielded a system which was capable of densities up to 14 pounds per gallon without the corrosivity encountered with ZnCl2 alone. Field experience has confirmed the severe corrosivity of the CaCl2-NaNO3 system. Two multicompletion wells with this mixture in the annulus suffered corrosion penetrations of the tubing in less than two years. 4.3.6

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© 1960 National Association of Corrosion Engineers
1960
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