# How to define a reasonable heat source term in a THM model in OGS?

Dear all,

I am testing the effects of the injecting fluid temperature on fault stability with a 2D THM model in OGS. But I am not sure how to give a reasonable heat source term in the prj?

For example, I want to inject cold water into a geothermal reservoir:
cold water temperature: 30℃ (303.15K)
geothermal reservoir temperature: 150℃ (423.15K)
injection rate: 1e-6 kg*m^(-2)*s^(-1)

Could anybody tell me how I can set this heat source term?

Best,
Rui

More specifically, I would like to know whether this method shown below to calculate the input value of heat source term is correct in OGS?

In other words, how could they define this point heat source Q is equal to 150W？How could they get this 150W? Is there any deriving proof?

Solved. Not ΔT, but T. It is because heat is always together with mass. Q should be like this,

In THM process, after my testings, I found when this Q is equal to 0, the temperature would not change; when Q is larger than 0, the temperature would go up; when Q is smaller than 0, the temperature would go down.

So, in summary, Q=cmT is correct in physical law side, but Q=cmΔT is used to set the temperature source term in my case.