Abstract
API(1) 5CT Grade L80, type 1 oil country tubular goods (OCTG), e.g. production tubing & casing, in non-sour, natural gas wells in East Texas failed after relatively short exposure times upon being placed in service. Laboratory failure analysis of failed tubing and casing from several wells determined that the L80 tubing failed from environmental cracking initiating in the body on the annular (O.D.) side of the tubing/casing. The laboratory testing also showed that the failed tubing and casing met compositional and mechanical requirements of API 5CT L80 and NACE MR0175/ISO15156 requirements for sour service. This paper describes in detail three case histories of L80 downhole environmental cracking failures and summarizes two cases of N80 casing failures, the production environments the tubing/casing were exposed to and the influence of material heat treatment and well treatment chemicals and production/stimulation environments on the susceptibility to environmental cracking.
