Discussion Forum

Dear all,

I was trying to simulation electromagnetic induction well logging and met a problem.

As showing in the attached figure 1, there are three loops that represent for one transmitter (the lower loop)and two receivers (the upper two). An edge current is applied in the lower loop to excite the e.m. field. I used the module of Electromagnetic Waves, Frequency Domain to simulate the e.m. field. After the calculation, I did a line integration on the upper two loops in order to calculate the induced voltage that can be recorded.

The simulated was done for different conductivity values of the block (it simulates rocks in the subsurface). I am expecting that the integral value should increase with increased conductivity value. Because from what I understand, induced voltage in the receiver should be directly proportional to rock conductivity. However, as I increase the conductivity of the block (rock matrix), the integration value decreased. I could not figure out what the problem is in the model, and here are some points that might have problem:

1. I am not sure whether the model is calculating the primary field that is created by the transmitter, or it also calculates the secondary field that is induced by the primary field. I think only the secondary field is needed to calculate the conductivity of the rock. If the secondary field affects, is it possible to separate these two fields?

2. I am not quite sure whether doing the line integration is right way to get the induced voltage if the physics set up is correct.

3. Would AC/DC module be a better choice than EMW frequency domain module in induction modeling?

Could you please provide me with some suggestions? Thank you so much. I really appreciate your help.