Detection and Quantification of Three-Dimensional Hydraulic Fractures With Horizontal Borehole Resistivity Measurements

摘要: This paper investigates the suitability of low-frequency borehole resistivity measurements for detecting and appraising hydraulic fractures. The effects logging tool's transmitter-receiver spacing, orientation, operating frequency, as well fracture's shape, cross-sectional area, dip, electrical-conductivity contrast with embedding formation, are quantified using an fast Fourier transform (FFT)-accelerated integral-equation solver. Simulation results a tool that consists one transmitter two receivers in homogeneous shale formation 1/3 S/m conductivity show following: 1) Longer spacings can differentiate larger fractures, while shorter detect smaller fractures; specifically, fractures up to ~1000 m 2 in area if 18 19.2 m away from transmitter, but this long-spacing configuration cannot than ~10 requires effective electrical fracture be 100 S/m. In comparison, small ~1 1.2 1.5 even is only 10 S/m, short-spacing distinguish area. 2) Coaxial sensitive same different shapes or dips. Transverse copolarized discern axially symmetric asymmetric ones; example, configuration, they elliptical aspect ratio 8 circular square their areas within to . Cross-polarized quantify dip become more angle increases; 15° dipping ~100 them, 60° range ~100-1000 3) mostly insensitive frequency Hz-1 kHz depend moderately on configuration. 4) relative strength measured signals proportional when ten times conductive compared rock formation. 5) Short-spacing exhibit higher resolution; long (4 m) each other (long-spacing) 6) complex networks, not major branches intermediate contribute shape magnitude signals; contributions mainly position branches.