The response of a four-arm caliper (dual caliper) log in a drilled section is shown in the figure. The borehole features associated with the three identified sections P, Q, and R are:
The response of a four-arm caliper (dual caliper) log in a drilled section is shown in the figure. The borehole features associated with the three identified sections P, Q, and R are:
Show Hint
- P: washout; Q: in-gauge hole; R: key-seat
- P: key-seat; Q: in-gauge hole; R: washout
- P: under-gauge hole; Q: in-gauge hole; R: washout
- P: dog-leg; Q: in-gauge hole; R: key-seat
The Correct Option is A
Solution and Explanation
- At P, both caliper traces shift to the positive side with increased separation, showing an overall enlarged borehole from erosion $\Rightarrow$ washout.
- At Q, both traces cluster near zero with minimal separation, indicating the hole is close to bit size $\Rightarrow$ in-gauge.
- At R, the two orthogonal calipers diverge strongly, with one reporting much smaller diameter (negative) while the other differs, indicating a slot-like, one-sided wear $\Rightarrow$ key-seat.
Therefore, the mapping is P: washout; Q: in-gauge; R: key-seat.
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