Title:
Numerical study of the influence of fluid viscosity on wellbore spalling in drained fractured rock
Numerical study of the influence of fluid viscosity on wellbore spalling in drained fractured rock
Author(s)
Jin, W.
Zhu, Cheng
Arson, Chloé
Pouya, A.
Zhu, Cheng
Arson, Chloé
Pouya, A.
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Abstract
The objective of this work is to model the influence of shear stresses induced by viscous fluid flow on wellbore
spalling. We simulated a drop of stress and pore pressure at the wall of a meter-scale borehole with a plane strain
Finite Element model. The rock mass was modeled as a jointed continuum. Block sliding was predicted from the
tangential displacements in the joint after the shear failure criterion was reached. Simulations show that: (1) Higher
far field stresses induce more normal stress in the joints, which prevents the occurrence of shear plastic strains in the
joints and reduces block sliding at the wall; (2) Shear stresses and consequent shear plastic strains that are induced by
viscous fluid flow in the joints are higher for higher fluid viscosities, and decrease over time as the blocks on each
side of the joint slide on each other; (3) In joints that are in contact with the borehole, a change of one order of
magnitude in the fluid viscosity results in a change in joint shear stress by a factor of 2. Results suggest that if
drainage had been simulated over a longer period of time or for a smaller borehole diameter, the failure criterion
would have been reached on a larger zone around the borehole, which could have a critical impact on the risk of
borehole spalling. The numerical approach proposed in this work is expected to be useful to recommend wellbore
operation modes so as to avoid excessive spalling and clogging.
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Date Issued
2015-07
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