Cryogenic tests with CO2 in the Tubular Testing System

Updating our equipment for testing at extremely low temperatures with CO2 posed multiple practical challenges. All have been solved in a pragmatic manner. Now, CCS test conditions can be applied safely and efficiently.

Jeroen Van Wittenberghe

Carbon Capture and Underground Storage (CCS) is a rapidly emerging solution for reducing CO2 emissions released into the atmosphere. CCS aims to capture CO2 at the emission source and then transport it to an underground permanent storage location. Possibilities for such locations include depleted gas reservoirs and unconnected aquifers. CO2 will be injected into these subsurface layers through wells that need to be capable of handling the CO2 flow safely and economically.

The oil and gas industry uses premium connections to join the casings and tubings sections that are used in well construction. Premium connections are threaded connections that include a metal-metal seal to ensure that the casing or tubing does not leak gas or liquid. The thread ensures sufficient mechanical strength to bear the loads the connection will be exposed to in the well during its service life. Standardised test protocols exist to qualify such premium connections for use in the oil and gas industry. As there are distinct differences in the behaviour of CO2 compared to hydrocarbons, the conditions in CO2 injection wells for CCS are outside the design envelope of these connections. Hence, OCAS has developed a new testing protocol specifically for CCS applications. Moreover, the full-scale test equipment has been modified to accommodate such tests. The main differences in the conditions are: The temperature in a CCS well can become very low, potentially as low as -80°C. This occurs primarily when liquid-gas phase changes are encountered and is explained by the Joule-Thomson effect. CO2 (and contaminants present in the captured stream) is potentially corrosive, also because of the potential condensation of contaminants in the well. Cyclic loading due to cycles in injection flow and the lifespan of the project can be more severe in number and magnitude than typically considered in oil or gas production cases. The above conditions can affect the connection performance because the low temperatures can result in embrittlement of the casing materials and thermally induced high-tensile loads can occur in the tubing and/or casing. Increased corrosion can affect the metal-metal seal and material strength, and CO2 acting as a solvent can affect the pipe thread lubricant. OCAS has updated the Tubular Testing System to allow full-scale testing at cryogenic temperatures using gaseous and liquid-phased CO2 as internal pressurisation medium. Next to this, the leak detection equipment has been updated to make it compatible with CO2 at very low temperatures. This allowed OCAS to perform CCS tests for a major oil and gas company.