The in-situ permanent expansion of casing and tubing is rapidly becoming implemented in oil and gas well completions. Over 25,000 feet of solid, not slotted, casing have been expanded downhole by one company since November 1999. Previous laboratory work has shown that tubular expansion affects the toughness of the final product; however, proper material selection of the product to be expanded can yield a final product with acceptable toughness. Recently, laboratory expansion of selected grades of seam welded and seamless OCTG steels has been used to study the effects of expansion (cold work) and strain aging on the hardness of five grades of C-Mn steels as well as on the susceptibility of four different heats of seamless P-110 tubing (also C-Mn) to sulfide stress cracking. Both cold work and strain aging were found to increase the hardness of these steels as well as dramatically reduce the susceptibility of the P-110 to sulfide stress cracking in an aqueous solution of 5wt% NaCl at a pH of 4.2 with a cover gas containing a partial pressure of H2S of <= 0.15 psi ( <= 1.0kPa). These results are significant because they also offer further insight into the effects of handling
damage or cold straightening operations on the performance of all high strength OCTG steels in sour production environments. New approaches to the evaluation of steels for sour service will be required to accommodate this phenomenon. Further study may determine how to "design" steels to be resistant to this effect.