Yl. Wang et E. Papamichos, CONDUCTIVE HEAT-FLOW AND THERMALLY-INDUCED FLUID-FLOW AROUND A WELL BORE IN A POROELASTIC MEDIUM, Water resources research, 30(12), 1994, pp. 3375-3384
Transient analytical solutions for temperature and pore pressure chang
es near a circular borehole under instantaneous temperature and fluid
pressure changes inside the borehole are presented. The solutions coup
le conductive heat transfer with Darcy fluid flow, and a borehole unde
r a nonhydrostatic far-field stress state is simulated. The heat condu
ction equation is decoupled from the coupled system of isothermal gove
rning equations, and the complete solution is obtained by superimposin
g this decoupled solution on the isothermal one. The solution is there
fore applicable to low-permeability media, where heat transfer is domi
nated by conduction only. Both cold and warm injection processes are s
tudied, and the applications to hydraulic fracture initiation and ther
mally induced fluid flow are discussed. Taking Westerly granite as an
example, it is concluded that the maximum thermally induced pore press
ure inside the rock formation can be 30% higher than the isothermal po
re pressure, with a borehole temperature and fluid pressure change rat
io (Delta T/Delta p) = 1 degrees C/MPa. It is emphasized that the ther
mally induced pore pressure change can be significant inside a low-per
meability porous medium, and a coupled solution must be obtained to ad
dress the mechanical, hydraulic, and thermal responses appropriately.