Cracking Tendencies of Two Martensitic Stainless Alloys in Common Heavy Completion Brine Systems at Down-Hole Conditions: a Laboratory Investigation Available to Purchase

There have been recent reports of failures of production tubulars in packer assemblies comprised of high-strength corrosion resistant alloys. This phenomenon is a result of the current trend of oil and gas development at deeper well depths and hotter down-hole temperatures. These failures have usually manifested themselves as cracking failures and resulted in severe economic penalties. While the consequences of these failures are straightforward, the causes are difficult to determine.

Here we report a laboratory investigation that clarifies the role of heavy brine compositions in cracking failures. Two different Martensitic stainless steels (85 ksi and 110 ksi) in the form of stressed C-ring coupons were tested in ten different heavy brine systems at 177⁰C (350⁰F). The different brine systems examined contained combinations of zinc and calcium cations, chloride and bromide anions, and standard additives for corrosion inhibition and oxygen scavenging. Tests were conducted on deaerated solutions under 500 psi pressures, both with and without CO₂ and H₂S. No cracking was found on any coupon challenged in an environment free of CO₂ and H₂S. Cracking of the 110 ksi steel was observed in chloride-only fluids when the acid gases were present. However, no cracking was observed in the brines comprised predominately of bromides under the same conditions. These results support the conclusion that low pH, common sulfur based additives and bromides, even under sour acid gas conditions, do not promote environmental cracking.