An essential part of the Carbon Capture and Storage (CCS) supply chain is the transportation of the CO2 in pipelines from the source to the sink. The understanding of the fluid behaviour as a function of pressure, temperature and composition is essential to ensure a robust and safe design of the transportation system. Within the oil and gas industry, dynamic fluid simulations are routinely performed to assess the requirements for safe- and cost-effective production and transportation systems, including lengthy subsea tie-backs.
The thermodynamic properties of a fluid however change dramatically from a typical hydrocarbon mixture to pure CO2. Additionally, the presence of impurities in a CO2-rich mixture has proven to have a major impact on the thermodynamic behaviour of the fluid. A CO2-rich fluid has a critical point at a pressure and temperature typically within the operating envelope of hydrocarbon production facilities and transportation systems. This thermodynamic characteristic makes the transportation of CO2-rich systems challenging as non-desired phase transitions may compromise stable operations and / or the mechanical integrity of the pipeline.
Accurate thermodynamic modelling of CO2-rich systems is therefore crucial. Only when simulation tools are able to predict phase transitions and thermodynamic properties with a higher level of certainty, the dynamic flow simulations will produce robust and reliable thermohydraulic results.
At Wintershall Dea we have developed an internal project to study the behaviour of a CO2-rich mixture during transportation and injection. In the first part of the presentation we will discuss the phase behaviour of CO2-rich mixtures in contrast to pure CO2 and how to describe this with commercial software tools. The second part shows the thermohydraulic behaviour of the system during its transportation along the pipeline and into a typical injection well to store the CO2 in a depleted gas or oil reservoir.