CO2 System Water Solubility and Water Condensation Rate Modelling for Pipeline Integrity Management

Abstract

In carbon capture and storage (CCS) projects, the fluid streams typically contain various impurities such as H2, N2, CO, Ar, O2, H2S, CH4 and also water. When it comes to transporting CO2 through pipelines, it is crucial to investigate the potential risks associated with hydrate formation and corrosion. These investigations often rely on the use of software modeling tools, and ensuring the accuracy of the model's parameters is of utmost importance. Key model parameters in relation to hydrate and corrosion risk include water solubility and hydrate dissociation temperatures. The accuracy of the modelling results would ultimately depend on the selection of the appropriate Equation of State (EOS) and polar model combination. This study shows how the optimal EoS model can be selected by comparing CO2 saturation pressure and solubility calculations, as well as hydrate formation temperatures, with various experimental data. This could lead to the selection of the most suitable EoS models and allow engineers to quantify the safety margin in a more effective manner. In addition, simulations were conducted to determine water solubility limits for CO2 rich fluids with various levels of impurities, providing insights into the distinct impact of each impurity has on water solubility. The impact of impurities and various design and operating factors on free water drop out along pipeline were demonstrated via a CO2 pipeline transportation case study. A separate depressurization study using a transient simulation was carried out to better understand the hydrate formation potential in such undersaturated CCS systems. In particular, the selection of most suitable EoS for CCS applications was discussed. Through this analysis it was possible to highlight the strength and limitation of various models which offers a new dimension in selecting the appropriate model.