Corrosion Resistant OCTG's and Matching Age-Hardenable Bar Products for a Range of Sour Gas Service Conditions

摘要

In selecting materials for corrosive sour oil field environments, the materials of choice must be reliable and cost-effective. Materials have to meet criteria for corrosion resistance and mechanical properties in service environments for the required service life. Both age-hardened nickel-base alloys and cold-worked solid solution nickel-base alloys offer many advantages such as high-strength, toughness and excellent corrosion resistance. Alloy 028 (UNS N08028), alloy 825 (UNS N08825), alloy G-3 (UNS N06985), alloy 050 (UNS N06950) and alloy C-276 (UNS N10276) are among the primary solid solution high nickel Corrosion Resistant Alloys (CRA's) currently used in the cold worked condition for Oil Country Tubular Goods (OCTG's) in sour gas wells. The primary CRA machining quality age-hardened bar products used with alloys 028 and 825 OCTG's for wellhead and subsurface completions of gas wells are alloy 925 (UNS N09925) and alloy 718 (UNS N07718). The primary CRA machining quality age-hardened bar product used with alloys G-3,050 and C-276 OCTG's for wellhead and subsurface completions of gas wells is alloy 725 (UNS N07725), the 120 ksi (827 MPa) minimum yield strength grade, and alloy 725HS, the 140 ksi (965 MPa) minimum yield strength grade. This paper presents guideline tables and graphs for cold-worked nickel alloys 028, 825, G-3, 050 and C-276 and age- hardened alloys 718, 925 and 725. The primary CRA machining quality age-hardened bar products used with OCTG's are ranked for a range of sour service conditions. Based on an extensive literature review of laboratory test and field data, the alloys have demonstrated corrosion resistance up to 230 deg C (450 deg F) depending on the chloride concentration, and H_2S content. Data are also included for alloy 686 (UNS N06686) and alloys 725 weld overlays and for alloy 25-6MO (UNS N08926) wire lines.