We numerically evaluate the possibility of using borehole electromagnetic measurements to diagnose and quantify hydraulic fractures that have been artificially generated in a horizontal well. Hydrofractures are modeled as thin disks perpendicular to the well and filled with either sand-based or electrically conductive proppant. The study focuses on the effect of thickness and length (radius) of hydrofractures to assess their effects on specific configurations of borehole-resistivity instruments. Numerical results indicate that several measurements (e.g., those obtained with low- and high-frequency solenoids) could be used to assess the thickness of a fracture. However, only low-frequency measurements performed with electrodes and large-spacing between transmitter and receivers (18 m) exhibit the necessary sensitivity to reliably and accurately estimate the length of long hydrofractures (up to 150 m) in open-hole wells. In the case of steel-cased wells, the casing acts as a long electrode, whereby conventional low-frequency short-spaced, through-casing measurements are suitable for the accurate diagnosis of long hydrofractures (up to 150 m in length).
Sensitivity analysis for the appraisal of hydrofractures in horizontal wells with borehole resistivity measurements