Abstract
This paper summarizes findings of a major experimental and analytical Joint Industry Program (JIP) that developed corrosion data and analyses for titanium alloys applicable to high pressure, high temperature (HPHT) wells. Testing conditions included: simulated production environments with H2S, CO2, chlorides and elemental sulfur, non-production environments (brine packer fluids and stimulation acids) and galvanic effects with other materials at temperatures up to 550 F (288 C). Included in this study were alpha-beta (a/ß) and beta (ß) titanium alloys, with yield strengths typically used in downhole tubulars and associated equipment in the range of 110 to 140 ksi (737 to 966 MPa) and in limited cases >150 ksi (1035 MPa). Most of the data development focused on the following alloys: UNS R56260, R56400, R56407, R56404, R56405, R58120 and R58640. Testing was mostly based on the slow strain rate technique with a modified evaluation procedure from that given in NACE TM0198. Packer fluid tests involved three primary fluid types: 16 ppg CaCl2/CaBr2/ZnBr2, 13.6 ppg CaCl2/CaBr2, and 14.2 ppg CaBr2. Acidizing tests involved exposure to 10% acetic acid and also a mixed acid environment consisting of 10% acetic acid and 10% HCl. Results from the program were used to augment a proprietary oilfield material selection software system developed from earlier JIP efforts.
