TABLE OF CONTENTS These logs indicate the presence of fractures if the laterolog 8 reads less than the induction curve (Schlumberger). The laterolog 8 is a vertically focused, short-spacing resistivity tool that may respond to thin bedded formations and/or to vertical fractures when they are filled with filtrate of resistivity lower than that of the formation.
The induction log reads horizontal conductivity, which is presented in the induction log as the inverse, i.e., as resistivity (R Il). Consequently the presence of fractures in the wall of a borehole might be detected if the laterolog 8 indicates less resistivity than the induction log.
Figure 3 10 shows an example of a fractured zone located with dual induction laterolog 8. Since the induction log depends on induced currents which, in general flow in horizontal loops, it can be concluded that the induction-log curve is affected negligibly by the conductive fluid-filled vertical fracture. This method must be used with care because R mf/R w ratio; resistivity of fluid in the fractures; fracture width, length, configuration, and lateral extent; lithology and porosity; shaliness; and borehole size affect the resolution of the method (Beck et al, 1977).
