  Squeeze cementing is a process used to repair leaking oil and gas wells, in
which a cement slurry is driven under pressure to fill an uneven leakage
channel. This results in a Hele-Shaw type flow problem involving a yield stress
fluid. We solve the flow problem using an augmented Lagrangian approach and
advect forward the fluid concentrations until the flow stops. A planar invasion
and a radial (perforation hole) invasion flow are studied. The characteristics
of the flow penetration are linked to the channel thickness profile. The
distribution of streamlines, flowing and non-flowing zones, evolves during the
invasion flow. An interesting aspect of the results is the extreme variability
in penetration metrics computed. These depend not only on the stochastic nature
of the microannulus thickness, which has significant natural variation in both
azimuthal and axial directions, but also on the ``luck'' of where the
perforation hole is, relative to the larger/smaller microannulus gaps. This may
explain the unreliability of the process.
