High CO2 Depressurization
Dry Ice Risk Analysis and Mitigations
Increasingly, operators are looking to exploit oil & gas fields rich in CO2 (>50-60 mol%). The main challenges introduced by high content of CO2 in the design of safety depressurization systems are:
- Complex thermodynamic behaviour:
- Physical properties that are not accurately predicted by standard equation of state methods
- Narrow phase envelope with dense phase depressurization – These result in large amounts of “boiling” liquid accumulated across the system, with a significant effect on metal wall temperatures.
- Formation of dry ice during depressurization leading to blockages.
- Use Validated gFLARE models for predicting fluid and wall temperatures.
- Use advanced EoS options such as GERG or SAFT-γ Mie, if required for accurate prediction of physical properties.
- Distributed / geometric approach to dry ice risk analysis and mitigations.
- Identify specific locations where dry ice formation potential exists, from either gas or liquid phase during depressurization.
- Use saltation correlations to determine if solids deposit in specific locations and whether blockage risks occur.
- Propose suitable design mitigations and operating philosophies to avoid formation of dry ice.