[Geoqus] Effective stress or Total Stress

[Manooch Salehabadi]

Dear All:

Hi

I have built up a plain strain model of well bore, the model is like a
two co-centre circles the inner circle is modelled by continuum elements
(CP8R) and the outer is modelled by continuum elements (CP8RP) with pore
pressure to simulate cement and formation around of it. The pore
pressure is 18 MPa and is constant. The contact between these two
circles are modelled by ABAQUS surface to surface interaction 

There are 20 Mpa fluid pressures inside of inner circle and I do not
know how I should model it.
 
I really confused how I should exert this pressure?

1-Should I exert this pressure as an effective pressure (effective
pressure=20 -18 (pore pressure)) or not?

2-If I want to exert this pressure directly on the formation elements
rather than on continuum element without pore pressure, again should I
exert it as an effective or total pressure?

Generally if I want to exert a fluid pressure on the porous element
should it be effective or total?


I will be really happy if you can help me 
You kind attention is much appreciated 

Regards
Manooch