Part 3 of 4 on Qualifying Casing Connections for Underground Hydrogen Storage
In part two, we discussed why material characterization in hydrogen environments is needed.
In part three we highlight the importance of test specimen selection and preparation for a full-scale connection qualification program.
The small-scale material characterization program described in Part 2 of this article series will characterize how hydrogen permeation affects the casing material performance. The full-scale testing program is designed to determine how these changes in material performance could impact the structural and sealability performance of the threaded connections.
There are two criteria to consider when evaluating casing connections for use in underground hydrogen storage:
- Overall structural integrity of the tubular and connection, and;
- Connection sealability under operating loads.
The selected casing connection design should be consistent with equipment used for high-pressure gas service. This will generally require the use of premium threaded connections, which include at least one radial metal-to-metal seal to provide the required sealability and structural strength.
To evaluate the repeatability of the test results, it is recommended that the test program include at least two full-scale test specimens, each consisting of one coupling with two threaded connections.
Full-scale test specimens should be prepared in accordance with API RP 5C5
“Procedures for Testing Casing and Tubing Connections”
which specifies minimum length requirements and connection geometry combinations such as thread and seal interference. Additional tests might be required depending on the number of connection geometry combinations to be evaluated. API RP 5C5 should be used as a guide for selecting connection geometry combinations for gas-tight performance.
