A New Chemical Mechanistic Postulate Regarding Annular Environmentally Assisted Cracking (AEAC) - Importance of Cations and Key Contaminants in Packer Fluids in Cracking of Martensitic Stainless Steel

摘要

Failure of production tubing in the oil & gas industry has become alarmingly more frequent in recent years in spite of the increased use of corrosion-resistant-alloy (CRA) materials. The majority of the recent failures have occurred from the outside (annulus side) and been attributed to Environmentally Assisted Cracking (EAC) - hence, best described as Annular EAC (AEAC). Examination of these failures points to a serious incompatibility of the production tubing metallurgy with the packer fluid under stress. To solve this problem, a research alliance of the co-authors to examine the compatibility of a wide spectrum of completion fluids with various martensitic stainless steel metallurgies was established. This unique research collaboration has resulted in a new body of knowledge regarding the causes behind AEAC failures. Results point to a key causative factor in AEAC not previously recognized. A new chemical mechanism distinct from the classical SCC or SSC has consequently been postulated to explain many AEAC observations. The mechanistic mode involves the effect of select cations and contaminants in the packer fluid. This paper discusses this new information and identifies serious misconceptions regarding the role of completion & packer fluids in the tubular failures.