CPG Exploration Techniques & Seismic Interpretation 2

Question 1

What does a flat spot on a seismic section typically indicate?

Accepted Answer

A horizontal fluid contact such as a gas-water or oil-water interface

Answer

Flat spots are horizontal reflections that cross stratigraphic dip and represent fluid contacts where acoustic impedance changes at the phase boundary.

Question 2

In seismic stratigraphy, what is an 'onlap' configuration?

Accepted Answer

Reflectors terminate against an underlying surface in an up-dip direction

Answer

Onlap occurs when initially horizontal or inclined strata terminate progressively against an inclined surface in an updip direction, indicating transgression or basin filling.

Question 3

Which seismic attribute is most directly related to pore fluid type?

Accepted Answer

Poisson's ratio derived from Vp/Vs ratio

Answer

Poisson's ratio (derived from the Vp/Vs ratio) is highly sensitive to pore fluid type because shear waves are less affected by fluid content than P-waves.

Question 4

What is the purpose of applying a Normal Moveout (NMO) correction in seismic processing?

Accepted Answer

To align reflections from the same subsurface point recorded at different offsets

Answer

NMO correction removes the hyperbolic moveout effect so that reflections from the same subsurface point at different source-receiver offsets can be stacked coherently.

Question 5

A geologist observes high-amplitude seismic anomalies (bright spots) in a gas-prone basin. Which scenario would cause a FALSE bright spot?

Accepted Answer

A tight carbonate with high acoustic impedance overlying a low-impedance shale

Answer

A hard kick from high-impedance carbonate over low-impedance shale produces a strong reflection that mimics a bright spot but contains no hydrocarbons.

(CPG) Certified Petroleum Geologist Practice Test

(CPG) Certified Petroleum Geologist Practice Test

CPG Exploration Techniques & Seismic Interpretation 2