Steel Grades
Past experience suggests that susceptibility to stress corrosion cracking of high strength steel is large. In order to avoid stress corrosion cracking, a variety of materials have been introduced to oil held tubing. They include: marten — sitic stainless steel, austenitic-ferrite stainless steel, high alloy austenitic stainless steel, nickel base alloys and titanium alloys. Chromium-containing martensitic stainless steel has also been used because of its resistance to corrosion in carbon dioxide environments. A stainless steel with 9(Л-12(Л chromium ran obtain a high level of corrosion resistance. Recently, these grades of casing and tubing have been offered with an AISI 420 composition (13СЛ chromium) and 80.000 psi minimum yield strength. Experience with these materials have been good (Wilhelm and Kane. 1987).
According to API classification casing grades, which have been found realistically applicable to oil field condition where IKS is present and ambient temperatures are encountered, are: J-55. C-15. N-80. MOD (modified) N-80. SIO-95. and P — 110 (Kane and Greer. 1977). Susceptibility to stress cracking decreases as the temperature increases. Hence as the temperature increases with increase in depth higher strength steel grade can be utilized, e. g.. SOO-140. Field experience also suggests that large concentration of H2S affects P-110 casings. (For details sec’ Jones, 1988.)