Seismic Exploration Depth Stretching
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Questions and Answers

What is the primary objective of interpolating input data to determine the value of YI at points XI?

  • To sort seismic data into Common MidPoint (CMP) gathers
  • To apply Normal Moveout (NMO) correction to seismic data
  • To increase the velocity analysis accuracy
  • To improve the Signal-to-Noise Ratio (SNR) in seismic data (correct)

    • What is the purpose of applying Normal Moveout (NMO) correction to seismic data?

  • To sort seismic data into Common MidPoint (CMP) gathers
  • To correct for the effects of velocity variations on seismic wave arrival times (correct)
  • To improve the spatial resolution of seismic images
  • To increase the frequency content of seismic data

    • What is the primary application of Common MidPoint (CMP) stacking in seismic imaging?

  • To generate high-resolution seismic images of the subsurface (correct)
  • To increase the velocity analysis accuracy
  • To sort seismic data into offset sections
  • To improve the Signal-to-Noise Ratio (SNR) in seismic data

    • What is the main benefit of sorting seismic data into offset sections?

    <p>To reduce the effects of noise on seismic data</p> Signup and view all the answers

    What is the purpose of velocity analysis in seismic imaging?

    <p>To determine the velocity structure of the subsurface</p> Signup and view all the answers

    What is the primary advantage of using Common MidPoint (CMP) stacking in seismic imaging?

    <p>To reduce the effects of noise on seismic data</p> Signup and view all the answers

    What is the main difference between onshore and offshore seismic data?

    <p>The complexity of the subsurface velocity structure</p> Signup and view all the answers

    What is the purpose of generating a Common Offset section?

    <p>To visualize the seismic data in a more meaningful way</p> Signup and view all the answers

    What is the primary benefit of using velocity analysis in seismic imaging?

    <p>To determine the correct velocity model for seismic imaging</p> Signup and view all the answers

    What is the main application of seismic imaging in the oil and gas industry?

    <p>To identify potential hydrocarbon reservoirs</p> Signup and view all the answers

    Study Notes

    Depth Stretching after NMO-Stack

    • Depth stretching maps the sample at time t0 into the sample at depth.
    • NMO removes the additional delay due to offset.
    • The corrected depth is calculated using the equation: z = sqrt(t0^2 + (h/V)^2).

    NMO-Stack: Imaging for a Flat Earth

    • NMO-stack is an imaging algorithm that assumes:
      • Reflectors are flat.
      • Layer velocities are constant.
    • When these assumptions are met, NMO-stack is suitable for imaging.
    • One CMP gather contributes to the image for a specific midpoint only.
    • NMO-stack is extremely fast and can be used for quick processing QC.
    • It is also used when layers are almost flat.

    NMO Correction

    • NMO correction involves calculating the corrected time using the equation: t_NMO(h) = t + 2h^2 / V^2.
    • The corrected time is used to calculate the corrected depth.

    CMP Gather

    • A CMP gather is a collection of seismic data with a common midpoint.
    • The data is sorted into CMPs, and NMO is applied, followed by stacking.

    Multiple Layers and Constant Velocities

    • In the presence of multiple layers with constant velocities, the NMO correction equation is used to calculate the corrected time.
    • The equation is: t_NMO(h) = t + 2h^2 / V^2.

    Matlab/Octave Code

    • The provided Matlab/Octave code calculates the NMO correction using the equation: dNMO(:,h) = interp1(t, data(:,h), tNMO).
    • The code iterates over each offset, calculates the corrected time, and then interpolates the data using the corrected time.

    Stack: SNR Improvement

    • The NMO corrected CMP gather is stacked to produce a final image.
    • The stacking process improves the signal-to-noise ratio (SNR).
    • The resulting image shows an improvement in SNR compared to the original CMP gather.

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    Related Documents

    theory_practice_migration_1_8.pptx

    Description

    This quiz covers the concept of depth stretching after NMO-stack in seismic exploration. It deals with the relationship between offset and depth.

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