Flow experiments were performed on a ten-inch diameter by fifteen-inch long thick-walled cylindrical sample of poorly consolidated sandstone, with a 1.25-inch diameter borehole. The purpose was to evaluate the effect of changing stress regimes on near-wellbore permeability and liner loading. A one-inch diameter screened liner was installed in the wellbore to preclude sand production. The liner was instrumented with strain gages, in order to determine stresses resulting from borehole deformation during production. The cylindrical sample was instrumented with pore pressure probes, placed at different distances from the wellbore, in order to assess variation in formation permeability with evolving effective confining stresses and production regimes. The major conclusions of this experiment are as follows:
if sand ablation does not occur and if an adequate annular space exists between the liner and the wellbore, load transfer to the liner is mitigated. If sand ablates and fills the annular gap, the complexity of the load transfer mechanism increases dramatically. This has been addressed elsewhere (Abou-Sayed et al., 1995; Willson and Abou-Sayed, 1998).
Apparent dilatant behavior in the near-wellbore region leads to permeability increase.
An intermediate interval experiences a reduction in permeability, due to stress transfer, following yielding of the inner zone, adjacent to the wellbore.