[Geoqus] borehole injection boundary conditions

[shengli chen]

Dear Geoqus members,
 
I am working on the borehole prolem but recently got stuck with the specification of the boundary conditions. Consider a borehole subjected at its surface r =  R (R is the borehole radius) to a uniform fluid injection rate q0, What should be the boundary condition at the borehole wall r = R looks like? (1) total radial stress sigma_rr = 0, shear stress sigma_rz = 0, and flux rate q = q0; or (2) total radial stress segma_rr = pore pressure p (which indicates zero Terzaghi effective stress), shear stress sigma_rz = 0, and flux rate q = q0???
 
If (1) is correct then we can easily impose q = q0 in the Abaqus and just do nothing with the sigma_rr = sigma_rz = 0. However, I think the boundary condtions (2) is more reasonable as the injection of fluid will be accompanied by an induced pore pressure thus the total radial stress segma_rr should be equal to the pore pressure p. If so, how can we assign at the borehole surface sigma_rr = p (both sigma_rr and p are unknown) or Terzaghi effective stress equal to zero in additon to q = q0??? In my understanding, the applied surface stress in ABAQUS should have a meaning of total stress for porous medium.
 
Thanks in advance for any advice!!!
 
Shengli


      
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.ruhr-uni-bochum.de/pipermail/geoqus/attachments/20090112/035cb44f/attachment.html>