Which log is used to determine borehole diameter and may help identify constrictions along the wellbore?

Which log is used to determine borehole diameter and may help identify constrictions along the wellbore?

• A. Gamma ray log
• B. Resistivity log
• C. Caliper log
• D. Neutron log

Answer: (C)

Measuring the borehole’s geometry along depth is the purpose here. A caliper log uses a tool with extendable arms that touch the borehole wall, recording the distance to the wall as it moves along depth. This creates a profile of borehole diameter and can reveal constrictions, enlargements, or washouts where the hole isn’t uniform. This information is essential for understanding where the hole is undersized or oversized, which can affect casing, cementing, and the interpretation of other logs. The other logs monitor properties of the surrounding rock rather than the hole itself: a gamma ray log detects natural gamma radiation to help identify lithology and shale content; a resistivity log measures how resistant the formation is to electrical flow to infer fluids; a neutron log responds to hydrogen content to estimate porosity. They don’t directly report borehole size, so the caliper log is the best match for identifying borehole diameter and constrictions.

Measuring the borehole’s geometry along depth is the purpose here. A caliper log uses a tool with extendable arms that touch the borehole wall, recording the distance to the wall as it moves along depth. This creates a profile of borehole diameter and can reveal constrictions, enlargements, or washouts where the hole isn’t uniform. This information is essential for understanding where the hole is undersized or oversized, which can affect casing, cementing, and the interpretation of other logs.

The other logs monitor properties of the surrounding rock rather than the hole itself: a gamma ray log detects natural gamma radiation to help identify lithology and shale content; a resistivity log measures how resistant the formation is to electrical flow to infer fluids; a neutron log responds to hydrogen content to estimate porosity. They don’t directly report borehole size, so the caliper log is the best match for identifying borehole diameter and constrictions.