Simulation of Carbon Dioxide Dense Phase Fluid Hammer Effect

Summary Carbon dioxide (CO2) transportation in its supercritical state has gained traction because of its efficiency. The challenge posed by CO2 fluid-hammer effects includes significant risks during operational processes, particularly during system shut-ins. A fluid hammer is a shock wave generated by the sudden cessation or reduction in fluid flow. When CO2 is compressed into its supercritical phase, modeling these shock waves becomes highly complex. These transient pressure surges, if unchecked, lead to potential system failures, including compressors and instrumentations. In this paper, we present a comprehensive study focused on the transient multiphase flow behavior in CO2 pipelines with an emphasis on characterizing fluid-hammer effects during system shut-ins. The study leverages fully transient flow simulations to model pressure transients and flow-rate variations under various operational conditions. Simulation results provide insights into the duration and magnitude of these pressure surges and their impact on surface systems. The study results show that CO2 fluid-hammer effects are highly dependent on the location of shut-in valves, pipeline diameter, CO2 flowrates, compressor stroke closing time, but less sensitive to the CO2 impurities and the elasticity of the pipeline material. Non-elastic walls predict higher pressures than reality, leading to a more conservative result. This study also helps the operator predict the timing when the compressor or mass flow source of CO2 will be shut -in, to avoid the pipeline pressure reaching beyond its maximum allowable operating pressure. This pioneering work addresses a critical gap in the knowledge of CO2 transportation by proposing robust modeling solutions that can be directly applied to surface-facility design and operational strategies. By enhancing the understanding of CO2 fluid-hammer effects, this study offers practical guidance for mitigating operational risks, improving system reliability, and supporting field operations such as pressure-transient analysis, facility maintenance, and workovers. The findings have significant implications for flow assurance and the overall safety and efficiency of CO2 pipeline systems.