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Abstract

In high pressure high temperature (HPHT) gas condensate wells the use of high density brines is required to ensure safe well operations during both well drilling and completion phases. This investigation studied the corrosion and environmental cracking behaviour of several high density brines in simulated HPHT conditions. The tested materials were low alloy steel grades P-110 and C-110, supermartensitic stainless steel (S13Cr) grade 110 ksi, duplex stainless steel, galvanized carbon steel wireline, duplex stainless steel wireline, superaustenitic stainless steel (N08535) and alloy 718. These materials were tested as single corrosion coupons, c-rings and four point bent beam specimens. A test program was embarked, selecting experimental conditions representative of future HPHT Field developments in the Norwegian Continental Shelf. The test results showed that S13Cr and duplex stainless steel suffered SCC failure in CaCl2 and CaCl2+CaBr2 brines at HPHT. The effect of corrosion inhibitor with these brines was variable, but acceptable to low alloy steels. It was also found that alloy 718 suffered a significant loss in ductility due to hydrogen embrittlement when exposed to caesium formate. But this did not result in cracking failures under the static loaded test conditions. S13Cr suffered both general and superficial pitting corrosion with evidence of initiation of SCC associated with the pits when exposed to caesium formate.