SPE Formation Evaluation and Logging 2

Question 1

Which neutron log measurement is most directly affected by the presence of gas in the formation?

Accepted Answer

Decreased neutron porosity reading

Answer

Gas has very low hydrogen index compared to water or oil, causing the neutron log to read anomalously low porosity in gas-bearing zones.

Question 2

What is the primary purpose of a caliper log in formation evaluation?

Accepted Answer

Determining borehole diameter and shape

Answer

The caliper log measures the diameter of the borehole, identifying washouts, key seats, and zones of good mudcake formation critical for correcting other log measurements.

Question 3

In a density-neutron crossplot, a gas crossover occurs when:

Accepted Answer

Density porosity exceeds neutron porosity

Answer

Gas crossover occurs when density porosity reads higher than neutron porosity due to gas having low density and low hydrogen index simultaneously.

Question 4

The formation factor (F) in Archie's equation relates to which petrophysical property?

Accepted Answer

Cementation and tortuosity of pore space

Answer

The formation factor F = R0/Rw reflects how the geometry, tortuosity, and cementation of pore channels affect resistivity relative to the pore fluid alone.

Question 5

Which log is most commonly used to identify fractures in a formation?

Accepted Answer

Fullbore Formation MicroImager (FMI)

Answer

The FMI (or similar microresistivity imaging logs) produces high-resolution borehole wall images that clearly reveal fracture orientations and apertures.

(SPE) Society of Petroleum Engineers Certification Practice Test

(SPE) Society of Petroleum Engineers Certification Practice Test

SPE Formation Evaluation and Logging 2