Abstract
The cold pilgered Pd-enhanced Ti-38644 titanium tubular represents an optimized production tubular product for worst-case deep sour gas well service. Tubular processing and heat treatment improvements have resulted in enhanced ductility, age uniformity, and thermal stability compared to first generation hot extruded Ti- 38644 tubulars. Alloy compositional enhancement with a minor Pd level, in conjunction with these microstructural improvements, have elevated both stress corrosion and crevice corrosion temperature thresholds to at least 246°C in worst-case sour gas well fluids. Excellent resistance in common chloride and bromide completion fluid brines is also observed up to at least 232°C in laboratory tests.
Specific guidelines for acidizing treatments and methanol injection in gas wells must be observed to assure compatibility with Ti-38644 tubulars. Suggested guidelines developed from laboratory testing of tubulars are presented.
Finally, a Pd-enhanced Ti-38644 titanium tubing string can offer substantial potential cost savings over a C-276 alloy string in very deep, high pressure, sour gas wells. This is derived from this titanium alloy’s unique combination of physical properties and higher design allowables at temperature, permitting downsizing of tubing and reduction or elimination of seal-bore assemblies.
