Temperature strange behavior

Dear TOUGH-community,

I am simulating CO2 injection into a saline aquifer using T2Well/ECO2N - the model geometry is attached. Initially, the model is under hydrostatic equilibrium, and the wellbore is filled with 100% water, while the caprock and reservoir - filled with 95% water and 5% NaCl. The caprock and reservoir have 10 layers of 5m each. The whole reservoir was perforated along its 50m thickness. The rate is 32 kg/s (1 million tonn/year).

When plotting the results, I get this behavior in the temperature proI get this behavior in the temperature profile (attached) when plotting the results (file attached). If going horizontally, we can see the temperature decreases due to convection, but if going vertically, the T increases until the perforation section. We can see strong cooling in the wellbore at the perforation section (about 30C), especially when going deeper to the bottom layer of the wellbore (last perforation with the reservoir). Could anyone help me understand this behavior, please? Is this related to wrong input or to the numerical simulation of T2Well? Or is it because of the reservoir layering that causes this behavior when colder CO2 (Tinj=35C reaches the warmer reservoir (70 C)?

PD: I have tried reducing the rate, and the temperature decrease is less. I also tried with 1 big reservoir layer,

Thanks!