Breakout measurement

Breakouts and tensile induced fractures (Section 6.4) can be identified and measured with borehole imaging tools (Fig. 6.12). Breakouts appear as wide bands of longer travel time or higher electrical resistivity in borehole images. Tensile fractures appear as narrow bands of longer travel time or higher electrical resistivity. Borehole images also permit identifying the direction of the stresses that caused such breakouts or tensile induced fractures. For example, the azimuth of breakouts coincides with the direction of $S_{hmin}$ in vertical wells.

Figure 6.12: Examples of wellbore breakouts and tensile fractures in borehole images. Learn more about wellbore imaging tools here: http://petrowiki.org/Borehole_imaging.

Breakouts can also be detected from caliper measurements. Caliper tools permit measuring directly the size and shape of the borehole (Fig. 6.13). Thus, the caliper log is extremely useful to measure breakouts and extended breakouts (washouts). For the same mud density, the caliper log reflects changes of rock properties along the well and correlate with other well logging measurements.

Figure 6.13: Example of caliper measurements to identify wellbore breakouts.