Titanium on its own is used for Helium storage vessels because of its extreme low-temperature capabilities. Carbon fiber on its own was used on the Space Shuttle liquid Oxygen and Hydrogen tanks. Both applications are low-temperature environments. The difference in the operating envelope in CCS wells and the aforementioned applications are the forces and stresses experienced in wells. However, Titanium shows an increase in tensile strength when cooled down (Source Kobe Steel).
Low Temperature Characteristics
Neither commercially pure titanium nor titanium alloys become brittle even at extremely low temperatures. In particular, commercially pure titanium and Ti-5AI-2.5Sn ELI can be used even at 4.2 K (-269°C)
Carbon fiber has a negative Coefficient of Temperature Expansion (CTE), reducing thermal effects and forces resulting from temperature fluctuations. Our resin used in CFST can safely be exposed to minus -40 degrees Celsius. As can be seen from this temperature profile simulation illustrated, it would make CFST perfectly suitable for the large majority of CCS wells. It will only go below minus -20C in exceptional cases. At a price around 13Cr tubing, the Operator will get superior service to duplex or Inconel properties, low-temperature coefficient, and low tubing weight.