Abstract
The possibility of dynamic failure and deterioration of the sealing capacity of critically stressed rock due to the infiltration of a compressible non-wetting phase fluid is examined through laboratory experiments. Rock samples were regarded as critically stressed under normal faulting conditions, and was set up to mimic the conditions of the cap rock just above a reservoir layer. Two kinds of external stress conditions were applied to the sample, i.e., close to an isotropic stress condition and close to a critical condition for failure. Air in a gas accumulator was infiltrated into the sample from the bottom end. Axial and circumferential strains of the sample and air pressure at the inlet were monitored during the experiment. Experimental results showed that the sample under stress conditions close to the critical condition became more deformable, resulting in failure, while that under a hydrostatic condition did not deform significantly and behaved elastically. An increase in the permeability of the critically stressed sample was also suggested. Understanding an in-situ stress state and considering a possible progressive failure of the cap rock are considered to be important when evaluating sealing capacity.
