EFFECT OF PERMEABILITY DISTRIBUTION ON MISCIBLE DISPLACEMENT IN A HETEROGENEOUS CARBONATE CORE

Three-dimensional miscible brine displacement simulations have been pe rformed for flow through a 10.2 cm (4 inch) diameter heterogeneous cor e containing a residual oil phase. The displacement front, as expected , is found to be a strong function of the permeability distribution as sumed for the core. The porosity and residual oil saturations were mea sured previously using X-ray CT. These experimental distributions were used as input for the simulations. Since the permeability distributio n cannot be measured directly in three dimensions for the core, two di fferent empirical relationships were used to estimate the permeability distribution based on the experimental porosity and residual oil satu ration distributions. The position of the saturation front is calculat ed and shown for various injection volumes for simulations using the t wo porosity-permeability relationships. Semilog and exponential porosi ty-permeability models were tested. For our case the semilog relations hip tends more toward the piston-like displacement, with only a couple of fingers developing. The exponential fit has a more irregular front . The two porosity-permeability models yield significantly different i n situ saturation distributions with roughly equivalent matches of the experimental effluent profiles from the displacement experiments. Thr ough the use of CT measured in situ saturations, the porosity-permeabi lity relationships were evaluated. The semilog relationship performed slightly better for the core studied even though both models gave equi valent results for the effluent profiles. This demonstrates the import ance of developing techniques such as CT which will monitor the in sit u saturations as well as the effluent saturations when attempting to d evelop and validate flow models.