Wave Reflection and Refraction

What can occur when the seismic data have not been correctly interpreted?

The 'bow tie' effect is produced

What is the primary purpose of mapping reflectors?

To create contour maps of the reflecting horizons

What is the term used to describe when the interpreter incorrectly jumps a reflecting horizon?

Leg

What type of maps are constructed from the reflectors picked on seismic lines?

Time maps Signup and view all the answers

What is the purpose of tracing reflectors from line to line in a loop?

To check that the reflector has been correctly picked Signup and view all the answers

What is the role of seismic surveying in petroleum exploration and production?

It is an essential part of the whole cycle Signup and view all the answers

What happens to some of the energy when a wave reaches a boundary between two media with different acoustic impedance?

Some of the energy is reflected back into the upper medium Signup and view all the answers

What is the relationship between velocity and density in a homogenous lithology?

Velocity and density generally increase with depth Signup and view all the answers

What is the range of possible values for a reflection coefficient?

-1 to +1 Signup and view all the answers

What is the characteristic of a strong reflector in terms of its reflection coefficient?

A reflection coefficient of +0.2 or -0.2 Signup and view all the answers

What is the reason for the occurrence of negative reflection coefficients?

A decrease in acoustic impedance across the reflecting interface Signup and view all the answers

What is the general tendency of the reflection coefficients at the boundary between two units?

They tend to appear with approximately equal frequency Signup and view all the answers

What is the primary purpose of 4D seismic surveys?

To monitor the movement of fluids during the life of a field Signup and view all the answers

What is seismic attribute analysis used for?

To make interpretations about reservoir characteristics Signup and view all the answers

What is the main application of seismic surveys in the petroleum industry?

To detect subsurface structures and reservoirs Signup and view all the answers

What is the term for the analysis of seismic data to identify patterns and trends?

Seismic attribute analysis Signup and view all the answers

What is the term for the use of seismic data to create a 3D model of the subsurface?

Seismic modeling Signup and view all the answers

How many geophysical methods are mentioned in the text?

8 Signup and view all the answers

What is the characteristic of oil in terms of uranium and thorium content?

High uranium but low thorium content Signup and view all the answers

What type of radiation is normally detected in geophysical work?

ɤ radiation Signup and view all the answers

Why are 'metalled' roads not suitable for radioactive surveys?

Because the radioactivity of the materials in the roads vitiates the observations Signup and view all the answers

What is the main factor contributing to the background radiation?

Cosmic rays, potassium-40, and uranium and thorium in rocks Signup and view all the answers

What is the minimum threshold for a reading to be considered significant?

3-4 times the background Signup and view all the answers

How are radioactive surveys typically conducted?

By walking along pre-laid lines holding the detector some 40-50 cm above the ground Signup and view all the answers

What is the primary reason behind the development of geophysical methods employing radioactivity?

To meet the demand for uranium metal in atomic reactors Signup and view all the answers

What happens to the energy of α and ß particles when they pass through matter?

It decreases exponentially with distance Signup and view all the answers

What is the approximate range of α particles in air at 18° C?

A few centimeters Signup and view all the answers

What can be used to completely stop β particles?

A thin sheet of lead Signup and view all the answers

What is the relationship between the intensity of γ rays and distance?

The intensity decreases exponentially with distance Signup and view all the answers

What is the scope of geophysical methods employing radioactivity?

Beyond just searching for ores of radioactive metals or minerals associated with them Signup and view all the answers