WorksheetsPetrophysics Raya Quiz
Total questions: 21
Worksheet time: 15mins
Which scenario is most likely to result in a higher Δt (μsec/ft) value in a sonic log?
High porosity sandstone with oil
Low porosity limestone with water
Compacted dolomite
Dense granite with no fluids
What is the relationship between Δt and acoustic velocity?
They are directly proportional
Both are constant
They are inversely proportional
No relationship exists
Using the Wyllie Equation, calculate sonic porosity for a formation with:
Δtlog = 85 μsec/ft,
Δtma = 55 μsec/ft,
Δtfl = 190 μsec/ft
0.10
0.22
0.27
0.32
Which unit is used to represent interval transit time in sonic logs?
ms
ft/s
μsec/ft
dB/m
Why might a gas-bearing formation show a “negative separation” between density and neutron logs?
Gas absorbs neutrons rapidly
Hydrogen index is high
Neutron log underestimates porosity
Gas has low hydrogen content
What is the effect of higher fluid density on gamma ray count in density logging?
What is the primary purpose of the neutron log in petrophysical analysis?
Given:
Bulk density (ρb): 2.50 g/cm³
Matrix density (ρma): 2.65 g/cm³
Fluid density (ρfl): 1.0 g/cm³
What is the porosity (ΦD) of the formation?
What does a high hydrogen index in a formation suggest in neutron logging?
High porosity with fluids
Absence of water
What abbreviation is commonly used for bulk density on a log?
RHOB
GR
DT
SP
Why might a shale show high neutron porosity but low true porosity?
Shales trap helium
Hydrogen in clays gives false high readings
Shale is denser than sandstone
Shale blocks neutron flow
In neutron logging, thermal neutrons are detected after losing energy due to:
Collisions with hydrogen atoms
Gas absorption
A formation with low bulk density and high neutron porosity might indicate:
Shale effect
Gas effect
Tight carbonate
Evaporite presence
Which tool combination would most reliably detect a gas-bearing zone?
SP and Gamma Ray Logs
Sonic and Caliper Logs
Neutron and Density Logs
Sonic and Resistivity Logs
In density logging, what happens to gamma ray count when the formation density increases?
What energy level defines a neutron as “thermal” in neutron logging?
1.0 eV
0.0205 eV
0.0001 eV
10 eV
Which of the following statements correctly describes a feature shown in the neutron log image?
The coal layer shows a neutron porosity reading of approximately 35%.
The sandstone gas zone exhibits a neutron porosity reading lower than expected due to gas effect.
The salt layer causes a high neutron porosity reading because of its low density.
The dolomite interval shows a neutron porosity of 18%, indicating very high porosity.
At a depth of approximately 7100 ft, what is the bulk density value observed from the log?
1.95 g/cm³
2.10 g/cm³
2.50 g/cm³
2.85 g/cm³
What is the neutron porosity reading in the gas-bearing zone?
35%
25%
10%
-5%
Why is the resistivity log critical in identifying the hydrocarbon zone in this well?
Hydrocarbons reduce resistivity
It confirms clay content in shales
It shows higher resistivity in hydrocarbon-bearing zones
It replaces the need for density logs
How does the neutron-density separation differ between the gas and oil zones?
The separation in gas zone is larger
The separation in oil zone is larger
The separation in gas zone is smaller
No separation in both zones
