REAL-TIME FRACTURE DETECTION AND FRACTURE ORIENTATION ESTIMATION

摘要

A method for determining existence of a fracture in a formation surrounding a wellbore drilled through subsurface rock formations includes calculating vertical resistivity, horizontal resistivity, apparent formation dip, apparent formation azimuth and axial resistivity for a plurality of longitudinal instrument spacings using measurements from a triaxial induction well logging instrument disposed in the formation. A spread in the axial resistivity values is determined and the axial resistivity spread threshold therefrom. Fracture indicator values and fracture orientation values are calculated from transverse components of the triaxial induction measurements. Presence of a fracture is indicated when at least one of the fracture indicator value exceeds a selected threshold, the axial resistivity spread exceeds the spread threshold and when the apparent formation dip exceeds a selected threshold.