Qualification of Tubulars and Connections for Use in Underground Hydrogen Storage

Abstract

Abstract With the scope of assessing the capability of Underground Gas Storage wells to manage gas blends starting from 10% Hydrogen content and defining a new "100% Hydrogen ready" design for new wells, a set of dedicated tests have been designed and executed to prove the suitability of tubulars and premium connections. The objective of this paper is to describe the procedure used for the tests and highlight the results qualifying the material for use with hydrogen. Connections pressure testing was split into two phases to cover the full well life cycle. In the first phase, connections were subjected to pressurization-depressurization cycles in 100% Hydrogen to simulate injection and production. The second phase followed the API RP 5C5 4th Edition CAL IV to simulate the real expected stresses, using He (as a pressurizing medium). Helium was chosen to represent hydrogen as both have small atom sizes, but helium is inert, which makes it safe to be used in a conventional full-scale test facility. For metallurgy testing, four-point bending (FPBT) and slow strain rate (SSRT) tests were conducted on a modified L80 Type 1 sample in 100%Hydrogen, 160 bar pressure and temperature between 10 °C and 60 °C, and including H2S and CO2 in the medium. The pressure tests showed no leakage in connection sizes performed even after 100 cycles with 100% Hydrogen at an internal pressure of 250 bar. The second phase of tests at ambient temperature with and without bending and using Helium was successfully performed without leaks. The FPBT results showed that the modified L80 Type 1 material was not susceptible to hydrogen embrittlement under the expected well conditions at 10 °C and 60 °C, even with higher hydrogen ion activity propitiated by the H2S in wet conditions. Some pitting was present, mainly associated with wet acidified environments in the presence of CO2. The dry environment did not produce any type of features. The SSRT results confirmed that an increased Hydrogen embrittlement effect is produced with the addition of H2S in wet environments, requiring a degree of conservatism with such an approach. With the move towards hydrogen use, premium connections and tubular materials for service need to be qualified. There are currently no standards covering this sort of application. Therefore, the work presents a comprehensive experimental approach to satisfactorily assess the suitability of connections and materials at custom conditions for their application.