Figure F19.
Resistivity-at-the-bit images of borehole breakouts (dark low-resistivity
parallel lines) at 1-in (shallow), 3-in (medium,) and 5-in (deep) penetration
from the borehole, 280-325 mbsf. Breakouts occur ~100 m above the frontal thrust
zone within log Unit 2. The high-conductivity breakouts indicate elongation of
the borehole in the direction of minimum horizontal compressive stress (
2
in this case). The two breakout lines occur opposite each other (~180° apart)
in the borehole. The orientation of breakouts (northeast-southwest, or
~220°-230°) is in good agreement with the plate convergence vector of
~310°-315° that would be expected to be in alignment with the maximum
compressive stress, 1.
Notice that the resistivity of the breakouts increases from the shallow to deep
image, suggesting minimal invasion and deformation 5 in away from the borehole.
