Anthropogenic CO2 transportation by carbon steel pipelines is one of the most discussed topics in the last decades to move the CO2 from the extraction/separation site to a storage reservoir. It is normally aimed at Enhanced Hydrocarbon Recover when injected in oil fields to increase the site production, at exploiting gas fields on which large amount of CO2 is present in natural gas mixture and, more in general, at reducing the CO2 anthropogenic emissions in atmosphere using the Carbon Capture Transportation and Sequestration solution. The latter is based in a first phase consisting in the separation of CO2 from the flue gases on the production plants and following transportation to specific sites where it can be stored in a safe way. Limited literature is available for CO2 transportation pipelines and only a few full-scale propagation tests have been performed worldwide. This is the reason why the approach to fracture propagation control for CO2 pipelines is also based on the experience gained for natural gas projects. However, some differences exist between natural gas and CO2 pipelines: - Higher operating pressure for CO2 pipeline to guarantee dense/liquid phase. - Different decompression behavior for the CO2 mixture due to change of phase from liquid to gas. - Larger influence on the decompression behavior of possible impurities inside the CO2 mixture with respect to the natural gas mixtures. One relevant issue is related to control the ductile fracture propagation which may be originated from a third-party damage, as well as corrosion flaws. In such cases, ensuring a crack arrest in a short length is fundamental to minimize any possible effects on outer environment and human beings. The fluid decompression occurring during fracture propagation represents the main driving force and, for dense-phase CO2, the plateau in the same decompression and its saturation pressure plays a key role in fracture control. In this paper, it is introduced the CO2 pipelines fracture control and is shown how the presence of impurities in CO2 produced by human activities strongly affect the saturation pressure and, consequently, the material fracture arrest ability. The effect of initial operating conditions is also discussed. Specific numerical tools are used to evaluate the CO2 decompression, able to calculate the thermodynamic and transport properties of industrially important fluids and their mixtures.

Anthropogenic CO2 dense phase decompression curve: role in fracture propagation control in pipeline transportation

ACS Spring Meeting 2021

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