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<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=081044509-15012009>Hi Shengli,</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=081044509-15012009></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=081044509-15012009>as you know on the surface of bore hole shear stress is
zero, about your first boundary condition "<FONT color=#000000>total
radial stress sigma_rr = 0, shear stress sigma_rz = 0, and flux rate q =
q0" </FONT><FONT color=#0000ff>, please impose a surface load
for example with Dload on the surface of borehole which normally comes from the
pressure of drilling mud or injection fluid so the Sigmar=0 then
asign surface flux rate or node flux rate depends on your
problem,</FONT></SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=081044509-15012009><FONT color=#0000ff> and when it comes to your
second boundary condition "<FONT color=#000000>total radial stress segma_rr
= pore pressure p (which indicates zero Terzaghi effective stress), shear stress
sigma_rz = 0, and flux rate q = q0" </FONT></FONT><FONT
color=#0000ff>again here</FONT></SPAN></FONT></DIV>
<DIV><SPAN class=081044509-15012009></SPAN><FONT face=Arial><FONT
color=#0000ff><FONT
size=2>impose appropriate flux rate depends on the type of your problem, for considering effective stress zero on the borehole wall please assin<SPAN
class=081044509-15012009>g</SPAN> <SPAN class=081044509-15012009>a
</SPAN>surface load through Dload<SPAN class=081044509-15012009>
as equal as pore pressure on the surface of the borehole then the effective
pressure on the surface of borehole is zero.</SPAN></FONT></FONT></FONT></DIV>
<DIV><FONT face=Arial><FONT color=#0000ff><FONT size=2><SPAN
class=081044509-15012009></SPAN></FONT></FONT></FONT> </DIV>
<DIV><FONT face=Arial><FONT color=#0000ff><FONT size=2><SPAN
class=081044509-15012009>I hope that it helps</SPAN></FONT></FONT></FONT></DIV>
<DIV><FONT face=Arial><FONT color=#0000ff><FONT size=2><SPAN
class=081044509-15012009></SPAN></FONT></FONT></FONT> </DIV>
<DIV><FONT face=Arial><FONT color=#0000ff><FONT size=2><SPAN
class=081044509-15012009>Regards</SPAN></FONT></FONT></FONT></DIV>
<DIV><FONT face=Arial><FONT color=#0000ff><FONT size=2><SPAN
class=081044509-15012009></SPAN></FONT></FONT></FONT> </DIV>
<DIV><FONT face=Arial><FONT color=#0000ff><FONT size=2><SPAN
class=081044509-15012009>Manooch </SPAN></FONT></FONT></FONT></DIV>
<DIV><FONT face=Arial><FONT color=#0000ff><FONT size=2><SPAN
class=081044509-15012009></SPAN></FONT></FONT></FONT><BR> </DIV>
<DIV class=OutlookMessageHeader lang=en-us dir=ltr align=left>
<HR tabIndex=-1>
<FONT face=Tahoma size=2><B>From:</B>
geoqus-bounces+manooch.salehabadi=pet.hw.ac.uk@lists.ruhr-uni-bochum.de
[mailto:geoqus-bounces+manooch.salehabadi=pet.hw.ac.uk@lists.ruhr-uni-bochum.de]
<B>On Behalf Of </B>shengli chen<BR><B>Sent:</B> 12 January 2009
21:41<BR><B>To:</B> geoqus@lists.ruhr-uni-bochum.de<BR><B>Cc:</B>
shengli.chen@yahoo.com<BR><B>Subject:</B> [Geoqus] borehole injection boundary
conditions<BR></FONT><BR></DIV>
<DIV></DIV>
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<DIV dir=ltr><FONT face=Tahoma color=#000000 size=2>
<DIV dir=ltr><FONT face=tahoma size=2>Dear Geoqus members,</FONT></DIV>
<DIV dir=ltr><FONT face=tahoma size=2></FONT> </DIV>
<DIV dir=ltr><FONT face=tahoma size=2>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???</FONT></DIV>
<DIV dir=ltr><FONT face=tahoma size=2></FONT> </DIV>
<DIV dir=ltr><FONT face=tahoma size=2>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.</FONT></DIV>
<DIV dir=ltr> </DIV>
<DIV dir=ltr>Thanks in advance for any advice!!!</DIV>
<DIV dir=ltr> </DIV>
<DIV
dir=ltr>Shengli</DIV></FONT></DIV></TD></TR></TBODY></TABLE><BR></BODY></HTML>