METHOD OF USING ELECTRICAL AND ACOUSTIC ANISOTROPY MEASUREMENTS FOR FRACTURE IDENTIFICATION

Measurements made by a cross-dipole acoustic logging tool in a borehole are processed to determine the principal directions of azimuthal anisotropy of a subsurface formation. Measurements such as in data tracks (601, 603) are als o made for correlation and comparison purposes of a Gamma Ray Log (621), a Caliper Log (623), a Density Log (631) and a Neutron Porosity Log (633). Measurements indicative of azimuthal resistivity logging variations and conductivity logging variations (605, 607, 609, 611) are also made with a multicomponent induction logging tool that is capable of performing electric al measurements at a number of different frequencies that also covers a range o f different downhole depths. These electrical measurements are processed using the principal direction determined from acoustic measurements to give an estimate of azimuthal resistivity variations. Based on modeling results, azimuthal resistivity variations are interpreted to estimate a fracture dept h in the rock for known fluids therein. >