Using a case study from the Sajaa Field, onshore Sharjah, United Arab Emirates (UAE), we devised several workflows to set up a fully thermal dynamic simulation case for carbon dioxide (CO2) storage in a depleted gas reservoir.
The construction of the thermal dynamic model started with the setup of dissolution tables for CO2. A published dataset to model CO2 dissolution was used. This was followed by the setup of enthalpy tables for each component of the equation of state (EoS). The thermal capacity of the reservoir and caprock formations was also computed while considering the mineral composition of the rocks. Additionally, the thermal conductivity of the formations was calculated and corrected for formation temperature, considering the mineral composition of the formation as well as the saturation of the rocks.
A thermal dynamic model enables the user to capture several important processes while injecting CO2 in a depleted gas reservoir. These processes include the wellbore changes of temperature due to expansion of injected fluid (Joule-Thomson cooling), the salting-out effect near the wellbore, and the impact of temperature and pressure changes on the rock mechanical properties for the reservoir and caprock.
Dissolution is one of the most important trapping mechanisms for CO2. To capture the CO2 dissolution accurately, it is important to capture the dissolution changes with pressure, temperature, and brine salinity. The thermal properties of the reservoirs are crucial to capture the heat transfer between injected CO2 and the rocks.
Several novel workflows were established during this study, including setting up dissolution tables for CO2 and impurities being injected, tabulating the enthalpy of each component, and computing reservoir and caprock formations’ thermal capacity and thermal conductivity. This paper will provide a complete guideline for thermal modeling for carbon capture and storage (CCS) projects in a depleted gas field.