Interpreting Synthetics and Pitfalls in Seismology

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What is the first step in the inversion preparation process?

Understanding the relationship between seismic data times and well borehole depths (correct)

Generating a set of Depth-Time curves

Reviewing various methods of deterministic wavelet extraction

Correlating well depths to seismic times

What is the purpose of Well-to-seismic tie in the seismic inversion workflow?

Establishing a reliable time to depth conversion for seismic data interpretation (correct)

Determining wavelet quality

Generating stable inversion wavelets

Conducting checkshot surveys

Why is Well-to-seismic tie important for deterministic wavelet extraction in the inversion workflow?

To rely on a good well-seismic match for stable inversion wavelets (correct)

To conduct checkshot surveys

To establish a correlation between well depths and seismic times

To generate Depth-Time curves

What type of data do checkshot surveys provide in the seismic inversion workflow?

Velocity of seismic waves at various depths along the borehole (A) Signup and view all the answers

In the Well-to-seismic tie process, what is involved in generating a set of Depth-Time curves?

Correlating well depths to Seismic times for each well (D) Signup and view all the answers

What role does the relationship between seismic data times and well borehole depths play in the seismic inversion workflow?

Understanding the time to depth conversion for seismic data interpretation (C) Signup and view all the answers

What type of information do VSP surveys provide directly beneath the wellbore?

High-resolution seismic information (A) Signup and view all the answers

What must be done before running sonic logging tools in a well?

Casing the loose near surface rocks (A) Signup and view all the answers

Why may the sonic log not perfectly match the seismic data?

The first layer velocity is unknown (A) Signup and view all the answers

What is extracted from the seismic data for the procedure of well-seismic tie?

Zero-phase statistical wavelet (A) Signup and view all the answers

What is computed by convolution of reflectivities with a zero-phase statistical wavelet in the well-seismic tie procedure?

Synthetic seismograms (B) Signup and view all the answers

What do global time shifts aim to improve in the well-seismic tie procedure?

Match with seismic data (B) Signup and view all the answers

Why is it important to consider elastic log quality in the well-seismic tie analysis?

A petrophysical revision before inversion study (A) Signup and view all the answers

What does the check shot correction aim to adapt to match surface seismic data?

Log time-depth curve (B) Signup and view all the answers

What is done with the drift curve during the check shot correction process?

It is interpolated to measure discrepancies (B) Signup and view all the answers

What does a zero offset synthetic trace typically consider?

The full stack or near-offset partial angle stack (D) Signup and view all the answers

What is the purpose of statistical wavelets extracted from seismic stacks?

To provide average seismic character in terms of amplitude and frequency spectrum (A) Signup and view all the answers

In the context of calibration, what is done if a residual time shift is detected between synthetic and seismic traces?

Apply the detected time shift to maximize the correlation (D) Signup and view all the answers

What should be done to improve the correlation in the 'Calibration / Stretch and Squeeze' step?

Stretch or squeeze the time-depth curve (B) Signup and view all the answers

Why is it important to limit the number of tie points in the 'Calibration / Stretch and Squeeze' step?

To prevent introducing a phase shift to the synthetic (D) Signup and view all the answers

What is a potential solution if large differences are observed between original and calibrated sonic logs?

Identify and remove bad points (A) Signup and view all the answers

What is the key principle when estimating phase shifts in seismic data?

Use different intervals for consistency checks (D) Signup and view all the answers

In the context of statistical wavelet extraction, what does a spectral analysis of the seismic provide?

Information on stationarity of the seismic signal (D) Signup and view all the answers

What is the main purpose of extracting statistical wavelets from seismic stacks?

Give average seismic character in terms of amplitude and frequency spectrum (A) Signup and view all the answers

In wavelet extraction, why should the analysis window be greater than twice the wavelet length?

To capture low-frequency information (D) Signup and view all the answers

What can be done if there are large differences between two sonic logs during calibration?

Check input information for possible errors (A) Signup and view all the answers

What is the main benefit of using the Roy White Algorithm for wavelet estimation?

Produces a series of diagnostic parameters to estimate reliability (A) Signup and view all the answers

In deterministic wavelet extraction, when is the Full Wavelet method typically used?

When several good events for correlation are available (C) Signup and view all the answers

What does the Proportion of Energy Predicted (PEP) measure in wavelet estimation?

Total energy in the seismic trace that can be predicted from well log reflectivity (B) Signup and view all the answers

Why is it recommended to extract single wavelets at each well during quality control?

To ensure the wavelets have similar phase and amplitude spectrum (B) Signup and view all the answers

What is the main difference between the Full Wavelet method and the Constant Phase method in deterministic wavelet estimation?

The Constant Phase method approximates phase as a constant value (B) Signup and view all the answers

What range does the Root Mean Square Error (RMSE) value typically fall into for an accurate wavelet?

0.0 - 0.5 (C) Signup and view all the answers

What is the primary advantage of the Constant Phase method over the Full Wavelet method in wavelet estimation?

It is more robust when logs do not tie well with seismic data (A) Signup and view all the answers

How is the amplitude and phase of the deterministic wavelet estimated in Roy White Algorithm?

Through cross-coherence analysis between seismic and synthetic reflectivity (D) Signup and view all the answers

'Given that tie location, determine the optimal wavelet.' Which step of the methodology does this statement refer to?

'Extracting the wavelet using well log data' (D) Signup and view all the answers

Why is it recommended to use multiple wells within a survey and the Multi-well (average) wavelet?

To generate stable inversion wavelets by comparing different well wavelets (B) Signup and view all the answers

Why is it critical to have a wavelet size that can describe frequencies down to 5Hz?

To prevent unstable results in the low-frequency range (B) Signup and view all the answers

What does it indicate if the phase spectra of a wavelet is not flat?

There is a mis-tie between the well and seismic data (C) Signup and view all the answers

Why does the inversion workflow rely on a good well-to-seismic match?

To ensure that the wavelet extraction is stable (A) Signup and view all the answers

What is the purpose of subjecting all extracted wavelets to Quality Control?

To compare between different wells and stacks (A) Signup and view all the answers

What is the significance of defining the correct wavelet scaling in the inversion process?

It enables accurate retrieval of reflectivity from inversion (B) Signup and view all the answers

Why is it important to know the phase and polarity of the seismic wavelet?

To correctly interpret seismic data by filtering through the wavelet (C) Signup and view all the answers

What is one of the pitfalls associated with synthetic seismograms mentioned in the text?

Failure to account for wavefront dispersion and absorption effects (B) Signup and view all the answers

What is a key difference between synthetic seismograms and actual seismic data mentioned in the text?

Synthetic seismograms involve only zero-offset traces (B) Signup and view all the answers

What is the general problem with wavelet extraction discussed in the text?

Issues with phase shifts and frequency content changes (D) Signup and view all the answers

Which approach uses both seismic data and wells to estimate the wavelet?

Deterministic estimation (C) Signup and view all the answers

What is involved in maximizing the match between wells and seismic during deterministic wavelet extraction?

Determining the seismic reflectivity convolutional operator (C) Signup and view all the answers

Why is the knowledge of the seismic wavelet crucial for interpreting seismic data?

To ensure the phase and polarity are correctly matched in the data (A) Signup and view all the answers

What must be done before extracting a deterministic wavelet using logs according to the text?

"Calibrate wells properly" (A) Signup and view all the answers

What strategy is recommended to address the 'chicken-and-egg' issue related to wavelet extraction according to the text?

Use zero-phase statistical wavelet for calibration (B) Signup and view all the answers

What does deterministic wavelet extraction aim to achieve according to the text?

Maximizing the match between well reflectivities and seismic data (A) Signup and view all the answers