ACOUSTIC SIGNATURES OF PATCHY SATURATION

We consider two saturation patterns in a partially saturated geomateri al. The first is the homogeneous pattern where saturation is the same at the pore scale at any location in the rock. The second is the patch y pattern where a large fully-saturated patch is surrounded by a dry r egion. In both cases the global saturation in a large volume of the-ro ck is the same. At the same global saturation, the effective acoustic properties of the rock vary depending on the saturation pattern. We of fer a practical method for identifying the dominating saturation patte rn from dynamic Poisson's ratio obtained from sonic well-log measureme nts. This method performs well in soft rocks whose acoustic properties are most sensitive to the way fluid is distributed in the pore space. (C) 1998 Elsevier Science Ltd. All rights reserved.