Wave Reflection and Refraction
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Questions and Answers

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

  • The interpretor is guaranteed to pick the correct reflector
  • Seismic lines are shot on a non-intersecting grid
  • Reflectors can be mapped accurately
  • The 'bow tie' effect is produced (correct)

What is the primary purpose of mapping reflectors?

  • To identify the location of seismic lines
  • To create contour maps of the reflecting horizons (correct)
  • To determine the type of rock present at the reflector
  • To calculate the depth of the reflecting horizon

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

  • Leg (correct)
  • Syncline
  • Isochron
  • Bow tie

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

<p>Time maps (B)</p> Signup and view all the answers

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

<p>To check that the reflector has been correctly picked (A)</p> Signup and view all the answers

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

<p>It is an essential part of the whole cycle (A)</p> 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?

<p>Some of the energy is reflected back into the upper medium (B)</p> Signup and view all the answers

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

<p>Velocity and density generally increase with depth (C)</p> Signup and view all the answers

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

<p>-1 to +1 (D)</p> Signup and view all the answers

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

<p>A reflection coefficient of +0.2 or -0.2 (C)</p> Signup and view all the answers

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

<p>A decrease in acoustic impedance across the reflecting interface (D)</p> Signup and view all the answers

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

<p>They tend to appear with approximately equal frequency (B)</p> Signup and view all the answers

What is the primary purpose of 4D seismic surveys?

<p>To monitor the movement of fluids during the life of a field (A)</p> Signup and view all the answers

What is seismic attribute analysis used for?

<p>To make interpretations about reservoir characteristics (A)</p> Signup and view all the answers

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

<p>To detect subsurface structures and reservoirs (D)</p> Signup and view all the answers

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

<p>Seismic attribute analysis (D)</p> Signup and view all the answers

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

<p>Seismic modeling (B)</p> Signup and view all the answers

How many geophysical methods are mentioned in the text?

<p>8 (D)</p> Signup and view all the answers

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

<p>High uranium but low thorium content (D)</p> Signup and view all the answers

What type of radiation is normally detected in geophysical work?

<p>ɤ radiation (C)</p> Signup and view all the answers

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

<p>Because the radioactivity of the materials in the roads vitiates the observations (B)</p> Signup and view all the answers

What is the main factor contributing to the background radiation?

<p>Cosmic rays, potassium-40, and uranium and thorium in rocks (C)</p> Signup and view all the answers

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

<p>3-4 times the background (A)</p> Signup and view all the answers

How are radioactive surveys typically conducted?

<p>By walking along pre-laid lines holding the detector some 40-50 cm above the ground (D)</p> Signup and view all the answers

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

<p>To meet the demand for uranium metal in atomic reactors (D)</p> Signup and view all the answers

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

<p>It decreases exponentially with distance (C)</p> Signup and view all the answers

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

<p>A few centimeters (D)</p> Signup and view all the answers

What can be used to completely stop β particles?

<p>A thin sheet of lead (D)</p> Signup and view all the answers

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

<p>The intensity decreases exponentially with distance (A)</p> Signup and view all the answers

What is the scope of geophysical methods employing radioactivity?

<p>Beyond just searching for ores of radioactive metals or minerals associated with them (A)</p> Signup and view all the answers

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