How should the enthalpy be correctly specified when simulating the process of air injection into an aquifer using TOUGH3/EOS3?
Hi
I am currently attempting to conduct a simulation for CAESA, specifically modeling the process of air injection into an aquifer. Due to persistent convergence issues, I have developed a small-scale model for debugging purposes. For example, in this case, I constructed a model approximately 244 m × 244 m in size, with a target aquifer thickness of 8 m, an overlying and underlying caprock of 10 m each, at a depth of approximately 800 m. The injection well is located at the top of the target layer, and air is injected at a rate of 1 kg/s for 20 days to form a cushion gas bubble. However, the results indicate that the temperature quickly rises, reaching up to 244°C. My injection enthalpy was set to 314,700 J/kg, and I have also experimented with adjustments around this value. According to the literature, the post-injection temperature should not be so high, yet the simulation clearly exhibits abnormal temperature behavior. I would like to know how to modify the model and understand the correct method for setting the injection enthalpy. I would be most grateful for any guidance you could provide.
Thank you!
2 replies
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Hello Hanking,
For your purpose, you have two ways to handle this:
1. You probably want to inject at a constant temperature. When you specify rate, the pressure changes, therefore, enthalpy (function of temperature and pressure) changes. Give the injection element a different rock type that has a large density (1.e50) so the temperature stays constant.
2. If you are curious, make a two element model mimic you injection element and reservoir element, set MOP(5)=9, printout secondary variables. The Enthalpy in TOUGH may have a different reference point than what you used.
Hope this helps,
YIngqi