Marti Bayer

Dear Colleagues,

We are modeling some field scale geothermal experiments using heat flow with FEFLOW 5.414. In our system, there is a pumping well and an injection well operating at the same rate. Injected water is previously heated and temperature evolution at several locations near the wells is recorded.

In order to report energy balances, we would like to quantify:
1- The amount of energy that is transported by advection in the downstream direction.
2- The amount of energy that is transferred to the atmosphere by convection.

The model is transient for both flow and heat transport.
We use the tool “budget analyzer” and define a control volume (POLIGON) within the model that contains both wells with the option “IMBALANCE”. Our  (transient) simulation is 30 days long.
At first, we want to quantify the total amount of WATER entering and leaving the control volume. There is water entering in the control volume through the lateral surface, water leaving the control volume through the lateral surface and water leaving and entering the control volume through the pumping/injection wells.
As output we get FLUX_IN(+),FLUX_OUT(-), ACC_MASS_IN(+) and ACC_MASS_OUT(-) as a function of time for the following variables: BC123_FLUXES, WELL_FLUXES, AREAL_FLUXES and IMBALANCE
WELL_FLUXES correspond to pumping and injection rates at the wells. BC123_FLUXES are inputs/output through node belonging to the boundaries. Since the control volume (polygon) is within the model domain and does not touch any boundary, there is no inflow/outflow through boundary nodes and therefore BC123_FLUXES is zero for all time steps. Similarly, since there is no recharge the value of AREAL_FLUXES is also reported as zero for all time steps.
According to the manual,
Imbalance = BorderIn + BorderOut + WellIn + WellOut + ArealIn + ArealOut
And then IMBALANCE is also zero for all time steps. (because BorderIn =BorderOut = ArealIn= ArealOut=0  AND WellIn =-WellOut).
All numbers make sense, but the problem is that the water entering/leaving  the model through the lateral area is not written. How can we quantify the total amount of water going through the control volume?

Any help will be highly appreciated.

Martí Bayer