90 Questions
What type of AVO anomalies are derived AVO attributes helpful in recognizing?
Class 3
Which attribute performed poorly due to predominantly class 4 AVO in the provided text?
Fluid Factor
What is the recommended way to examine the AVO response according to the text?
Combine intercept and gradient for derived AVO attributes
Which inversion method provided better results compared to amplitude/reflectivity methods?
Gradient inversion
Why do near/far stack operations and intercept-gradient product not yield meaningful results?
Due to class 4 AVO predominance
What is the primary purpose of generating angle gathers from offset gathers?
To analyze amplitudes and their variation with offsets
Why are super-gathers formed by combining adjacent locations in both inline and crossline directions?
To form windows of different sizes based on data quality
Why is it recommended to create super-gathers with adjustments for the structural dips in the case of steep dip horizons?
To avoid signal degradation
Which technique is suitable for examining large volumes of data in AVO analysis?
Comparing near-offset, mid offset, and far offset stacks
What is the main advantage of forming different offset or angle range-limited stacks?
To display pre-stack information in a more compact way
How are angle gathers related to offset gathers in AVO analysis?
Angle gathers are generated from offset gathers using a transform that needs a velocity model
What are the basic AVO attributes that can be calculated from seismic gathers?
Intercept and Gradient
How are AVO attribute stacks primarily used in seismic data analysis?
To locate anomalous amplitude behavior
What does the Aki-Richards equation predict in relation to AVO attributes?
A linear relationship
In the context of AVO analysis, what does a negative Gradient (B) value indicate?
Low acoustic impedance
What do Class 2 gas sands typically exhibit in terms of impedance contrast?
Near-zero impedance contrast
Which mathematical operation results in the AVO Product, a potential hydrocarbon indicator?
Multiplication of Intercept and Gradient
What is Scaled Poisson’s Ratio Change derived from?
Shuey’s equation
How do Class 1 gas sands behave with increasing offset?
Peak decreases and changes polarity
What does the AVO Sum (A+B) show at the top and base of the reservoir?
Negative response at the top and positive response at the base
What can be used as a tool for prospect reconnaissance of Class 3 gas sands?
Scaled Poisson’s Ratio Change
Which attribute is not affected by fluid changes but only by changes in matrix or lithology?
AVO Difference (A-B)
What attribute is based on Castagna’s Mudrock equation and highlights potential hydrocarbon zones?
Fluid Factor
In the Fluid Factor attribute, what do deviations from Castagna’s Mudrock line indicate?
Other lithologies and/or pore fluids
Match the following seismic processing effects with their descriptions:
NMO Correction = Correction of reflection arrival times to match those of the zero-offset trace Residual NMO = Common reason for distorted AVO response due to inaccurate velocity analysis or azimuthal velocity variations NMO Stretch = Stretching of individual events and broadening of wavelet shape at further offsets Migration = Corrects moveout and requires an accurate velocity model
Match the following noise-related terms with their descriptions:
Reverberations = Cause interference of the primary wavefield by creating 'multiples' Tuning effects = Can cause interference with primary wavefield and tuning effects Processing Noise attenuation = Techniques to attenuate noise while preserving primary amplitudes Directivity of source wavefield = Effect related to orientation of directionally sensitive receivers
Match the following concepts related to seismic data analysis with their definitions:
AVO Analysis = Qualitative tool to detect anomalies by preserving relative amplitudes as a function of offset Intercept and Gradient = Parameters used to analyze the AVO response from seismic data Offset-dependent Reflectivity = Reflectivity that may be distorted by residual NMO or NMO stretch AVO Product = Result of mathematical operation used as a potential hydrocarbon indicator
Match the following physical effects in seismic processing with their impact on data quality:
Attenuation, dispersion, transmission effects = Can contribute to changes in amplitude due to wave spreading or subsurface interactions Noise interference = Can obscure desired signal amplitudes and cause interference with primary wavefield Residual Moveout correction = Phenomenon that distorts offset-dependent reflectivity and should be addressed Correct focussing and positioning of primary signal = Important for processing techniques to achieve while correcting for noise
Match the following concepts related to AVO analysis with their effects on seismic data:
Distorted offset-dependent reflectivity = Result of residual NMO or NMO stretch phenomena that need to be addressed Sparse velocity analysis = May lead to residual NMO distortion in AVO response and requires denser analysis Higher order corrections = Applied to reduce impact of residual NMO in AVO analysis AVO Attribute stacks = Primarily used in seismic data analysis for qualitative detection of anomalies
Match the seismic noise type with its description:
Random noise = Uncorrelated spatially and cannot easily be modelled Coherent noise = Annotated by dashed lines indicating greater move out than flat primary events Ground roll = Linear noise energy affecting near offsets Multiples = Crosscutting primary signal and causing amplitude effects varying with offset
Match the seismic processing step with its purpose:
NMO Correction = Addressing NMO stretch to prevent frequency distortion Noise Attenuation = Removing random noise and improving signal-to-noise ratio SuperGather Formation = Reducing random noise and preserving offset-dependent amplitude variations Post Imaging Processing = Preparing data for AVO analysis by attenuating multiples and distortions
Match the seismic attribute with its impact on AVO analysis:
AVO gradients = Restricting range of angles and increasing error of estimated AVO attributes Multiple attenuation = Impacting AVO analysis by causing interference on amplitude effects varying with offset Ground roll attenuation = Affecting near offsets and impacting true primary AVO measurement Structural dip smoothing = Smoothing out structural variations in steep dip locations
Match the seismic data feature with its corresponding method for improvement:
Gradient section anomalies = Method attempting to remove NMO stretch effects Flat seismic events obscured by noise = Forming SuperGathers to reduce random noise Multiple energy interference = Attenuating multiples before AVO analysis Ground roll amplitude distortion = Post imaging processing prior to AVO analysis
Match the seismic data visualization with its corresponding purpose:
Gradient section after NMO correction = Illustrating anomalous AVO gradients in red in shallow section Synthetic forward modelled gather = Showing predicted AVO response for comparison SuperGathers for noise reduction = Preserving offset-dependent amplitude variations Amplitude Vs incidence angle plots = Used for analyzing amplitude distortion before and after processing
Match the seismic amplitude processing technique with its description:
NMO correction = Correction for the velocity variation with offset Trace Muting = Elimination of noisy or unreliable traces Noise removal = Process to eliminate unwanted signal interference Amplitude-preserved processing = Technique that maintains the original amplitude values
Match the seismic amplitude distortion type with its category:
Wave propagation and geologic effects = Phenomena related to natural geological structures and wave behavior Acquisition and noise effects = Phenomena caused by data collection and external disturbances Processing artifacts = Issues introduced during data processing steps Energy losses during travel = Attenuation of seismic waves through subsurface materials
Match the seismic amplitude processing goal with its objective:
Estimate and remove energy losses = Ensure accurate representation of subsurface properties Remove noise effects = Enhance data clarity by eliminating unwanted disturbances Avoid processing-related artifacts = Prevent artificial distortions in the data Preserve amplitude changes = Maintain the true amplitudes for reliable interpretation
Match the seismic amplitude factor with its main cause:
Factors affecting seismic amplitudes = Categorized by their primary causes Factors related to wave propagation = Influences from natural geological and wave phenomena Factors due to acquisition noise = Disturbances introduced during data collection Processing-induced factors = Artifacts introduced during data processing
Match the AVO analysis term with its definition:
Amplitude-preserved processing = Approach to maintain original amplitude values True-amplitude processing = Technique ensuring accurate representation of subsurface properties AVO anomalies recognition = Identifying abnormal variations in seismic amplitudes Angle gathers creation = Generating seismic data grouped by reflection angles
Match the seismic amplitude correction method with its purpose:
NMO correction = Compensate for velocity differences at various offsets Trace Muting = Eliminate noisy traces for cleaner data analysis Noise removal = Get rid of unwanted signal disturbances for clearer interpretation Processing artifacts removal = Eliminate distortions introduced during data processing
Match the seismic data processing technique with its description:
AVO Analysis = Involves extracting amplitude and phase information from seismic data NMO Correction = Corrects for the differences in arrival times of seismic waves Trim Statics = Aligns traces within a time window using time shifts Super-gathers = Combine adjacent locations in both inline and crossline directions
Match the AVO attribute with its characteristics:
Gradient (B) = Measures the rate of change of amplitudes with offset Intercept (A) = Measures the zero-offset response Fluid Factor = Affected by changes in matrix or lithology AVO Sum (A+B) = Shows amplitude changes at top and base of reservoir
Match the AVO moveout term with its definition:
Two term NMO = Application of the first 2 terms in the NMO equation Higher Order NMO = Includes terms raised to the 4th power of velocity Time-variant Trim Statics = Performs cross-correlation over smaller, overlapping windows Conventional Trim Statics = Calculates a single time shift for each trace in a gather
Match the seismic event alignment technique with its features:
Conventional Trim Statics = Limited by calculation windows, may not align separated events Time-Variant Trim Statics = Interpolates shifts over overlapping windows for consistent flattening NMO Correction = Requires correct velocity for flat gathers and peak amplitude extraction Super-gathers = Combine data from adjacent locations to create more comprehensive datasets
Match the description with the correct AVO anomaly correction method:
Trim Statics - Conventional = Calculates single shifts for trace alignment within a time window Trim Statics - Time-variant = Performs cross-correlation over smaller, overlapping windows and interpolates shifts Super-gathers = Combine data from adjacent locations to improve overall alignment NMO Correction = Corrects for differences in arrival times to ensure flat gathers
Match the following terms with their descriptions:
Residual moveout effects = Addressed to flatten events in seismic gathers Ground roll = Distorts near-offset traces and has high amplitude NMO stretching = Related to Normal Moveout, can distort offset-dependent reflectivity Trace Mute = Used to limit the influence of long offset traces in stack processing
Match the following actions with their impact on AVO analysis:
Aggressive ground roll removal = Causes decrease in primary amplitudes and false AVO interpretation Noise removal = Can lead to a distortion of the AVO response if not performed carefully Muting in traditional processing = May restrict the maximum range of angles for AVO analysis Unmuting data = Recommended before AVO analysis to keep the range of offsets wide
Match the following statements with their recommendations for AVO analysis:
Energy losses and noise effects = Should be estimated and removed during seismic-data processing Effects of the near surface = Should be removed to avoid processing-related artifacts Muting in traditional processing = Should be done separately from that used for generating stacks in AVO analysis Factors affecting amplitudes in pre-stack domain = Must be understood and considered before running an AVO analysis
Match the following factors with their effects on amplitude variability:
Pre-imaging processing = Shows great variability in amplitudes but matches general trend Post-imaging processing = Produces more consistent plots with better attenuation of noise and energy Class 3 AVO response = Does not match with synthetic response in near and middle angle range Class 4 AVO response = Performed poorly due to predominantly in the text
Match the seismic amplitude distortion type with its category:
Wave propagation and geologic effects = Category 1 Acquisition and noise effects = Category 2 Processing artifacts = Category 3 Energy losses during subsurface travel = Category 1
Match the seismic amplitude correction method with its purpose:
NMO correction = Correct for wave propagation effects Trace muting = Remove noise effects Noise removal = Eliminate acquisition-related distortions Amplitude-preserved processing = Avoid processing artifacts
Match the seismic amplitude factor with its main cause:
Noise effects = Acquisition-related distortions Wave propagation effects = Energy losses during subsurface travel Geologic effects = Wave propagation and geologic effects Processing artifacts = Errors introduced during data processing
Match the AVO moveout term with its definition:
Gradient (B) value = Indicator of fluid properties AVO sum (A+B) = Shows variations at top and base of reservoirs AVO product = Potential hydrocarbon indicator Scaled Poisson’s Ratio Change = Derived from rock properties changes
Match the seismic event alignment technique with its features:
Near/far stack operations = Aligns seismic events for better interpretation Intercept-gradient product = Attempts to align events using gradients Super-gathers formation = Combines adjacent locations for comprehensive analysis Angle gathers creation = Generates data for AVO analysis based on offsets
Match the seismic attribute with its impact on AVO analysis:
Fluid Factor attribute = Highlights potential hydrocarbon zones Class 2 gas sands behavior with offset = Impacts impedance contrast understanding Class 1 gas sands behavior with offset = Influences AVO Sum (A+B) results Derived AVO attributes for anomaly recognition = Helps in identifying specific AVO anomalies
Match the following seismic event alignment techniques with their descriptions:
Conventional Trim Statics = Calculating a single time shift for each trace in the gather to align traces within a time window Time-Variant Trim Statics = Performing cross-correlation calculation over smaller, overlapping windows and interpolating the shifts for a more consistent flattening
Match the seismic attribute correction methods with their characteristics:
Super-gathers = Combining adjacent locations in both inline and crossline directions for better analysis Trim Statics = Applying time shifts to align traces within a gather, constrained by the Normal Moveout equation
Match the seismic amplitude correction techniques with their purposes:
AVO Sum (A+B) = Highlighting potential hydrocarbon zones by summing the intercept and gradient attributes AVO Product = Mathematical operation indicator for hydrocarbons, based on the intercept and gradient attributes
Match the seismic processing issue with its impact on AVO analysis:
Residual moveout effects = Distortion of near-offset traces High amplitude noise = Restriction of angle range NMO stretching = Removal of energy losses Noise removal = Distortion of AVO response
Match the seismic attribute processing step with its purpose:
Trace Mute = Optimum stack production Ground roll removal = Limit influence of long offset traces Energy loss estimation = Avoid processing-related artifacts Muting in traditional processing = Restrict maximum angle range
Match the seismic moveout terms with their definitions:
Higher Order NMO = Applying corrections related to anisotropy and velocity heterogeneity using terms beyond the standard NMO equation Two Term NMO = Utilizing the first 2 terms of the NMO equation to correct for moveout, with an optional additional 4th order term
Match the seismic processing steps with their purposes:
Gather Flattening using NMO = Correcting non-flat gathers by applying NMO correction based on velocity models Cross-correlation = Calculating time shifts to align traces within a gather for improved data consistency
Match the seismic amplitude correction method with its objective:
AVO analysis = Estimate and remove energy losses Super-gathers formation = Remove noise effects Amplitude vs angle plot = Remove near-surface effects Wave propagation factors = Avoid processing-related artifacts
Match the seismic data visualization technique with its purpose:
Amplitude vs angle plot = Show impact on data quality AVO attribute stacks = Highlight hydrocarbon zones AVO Sum (A+B) = Examine amplitude variability Negative Gradient (B) value = Prospect reconnaissance of gas sands
Match the AVO anomaly corrections with their impacts on seismic data quality:
Trim Statics = Addressing residual non-flatness after NMO correction to improve alignment Higher Order NMO = Reducing deviations in seismic events across gathers, especially at far offsets
Match the seismic noise types with their descriptions:
Class 1 gas sands = Exhibiting behavior indicating gas presence as offset increases Class 2 gas sands = Showing typical impedance contrast characteristics related to gas presence
Match the seismic amplitude distortion type with its effect on seismic data:
Noise effects removal = False AVO interpretation Class 3 AVO response mismatch = Decrease in primary amplitudes Ground roll distortion = Great variability in amplitudes Structural dip adjustment = Residual moveout correction
Match the seismic event alignment technique with its impact on wave propagation:
Class 1 gas sands behavior = Variability in amplitudes Fluid changes effect = Energy better attenuated Scaled Poisson’s Ratio Change = Random noise attenuation Intercept-gradient product result = Meaningful AVO interpretation
Match the AVO analysis terms with their definitions:
AVO Intercept = Measures the zero-offset response of amplitudes AVO Gradient = Indicates the rate of change of amplitudes with offset
Match the seismic data processing techniques with their descriptions:
NMO Correction = Aligning events by applying corrections based on velocity models Interpolated Shift Corrections = Applying time-variant series of shifts to traces for consistent flattening
Match the seismic amplitude distortion types with their categories:
AVO Anomalies = Incorporate amplitude and phase changes, resembling time shifts in analysis Fluid Factor Deviations = Indicate variations from Castagna’s Mudrock line, highlighting potential hydrocarbon zones
Match the seismic noise type with its description:
Random noise = Uncorrelated spatially and cannot easily be modelled Coherent noise = Causes interference affecting the amplitude of seismic events Linear noise energy = Represents seismic wave travelling in the very shallow sub-surface Ground roll = Affects just the near offsets and interferes with primary signal
Match the seismic processing effect with its description:
SuperGather formation = Reduces random noise and preserves offset-dependent amplitude variations NMO correction = Stretches traces as a function of time and offset, causing frequency distortion Far offset muting = Prevents lower frequency events from affecting stack resolution Multiple attenuation = Reduces amplitude effects caused by events with greater moveout than primary signals
Match the AVO analysis term with its definition:
AVO anomaly = Anomalous AVO gradients observed in seismic sections AVO attribute = Quantitative measurement derived from amplitude variation with offset or angle AVO moveout = Variation in moveout time of seismic reflections due to changes in rock properties AVO product = Result of multiplying intercept and gradient values from AVO analysis
Match the seismic amplitude distortion type with its category:
NMO stretch = Shifts events to lower frequencies, affecting event amplitudes Amplitude effect from multiples = Interference affecting event amplitudes based on offset variations Linear noise energy (ground roll) = Affects near offsets and interferes with primary signal amplitudes Coherent noise interference = Crosscuts primary signals, causing amplitude variation
Match the seismic attribute with its impact on AVO analysis:
Fluid factor attribute = Indicates deviations from Castagna’s Mudrock line related to fluid changes Impedance contrast attribute = Helpful in recognizing Class 2 gas sands based on impedance differences Poisson’s Ratio Change attribute = Derived from Scaled Poisson’s Ratio Change for AVO analysis AVO sum (A+B) attribute = Shows top and base reservoir characteristics in AVO analysis
Match the seismic amplitude processing technique with its description:
AVO attribute stacks = Primary use is for quantitative analysis of amplitude variations with offset or angle Angle gathers from offset gathers = Used to examine AVO response based on different angles of incidence Intercept-gradient product calculation = Results in AVO Product which is a potential hydrocarbon indicator Near/far stack operations = Do not yield meaningful results in AVO analysis due to various factors
Match the physical effects in seismic processing with their impact on data quality:
NMO correction stretch functions = Result in frequency distortion, shifting events to lower frequencies SuperGather formation on steep dips = Can smooth out structural variations by stacking adjacent locations Noise attenuation techniques = Reduce random and coherent noise to improve signal-to-noise ratio Ground roll amplitude distortion near offsets = Interferes with primary signal amplitudes, impacting measurements
Match the following concepts related to AVO analysis with their effects on seismic data:
Class 1 gas sands behavior with increasing offset = 'Gas sands exhibit increasing negative intercept values as offset increases' AVO anomaly recognition using derived attributes = 'Helps recognize different types of AVO anomalies in seismic sections' AVO attribute impact on seismic data interpretation = 'Quantitative measurements provide insights into subsurface rock properties' AVO moveout term understanding for reflection patterns = 'Variation in moveout time helps understand rock property changes'
Match the seismic data feature with its corresponding method for improvement:
Seismic flat events obscured by random noise = 'Partial stacking using SuperGathers can improve S/N ratio' Coherent noise crossing primary signals causing interference = 'Multiple attenuation techniques can reduce amplitude effects' Strong linear noise energy affecting near offsets interfering with signal amplitude = 'Ground roll removal methods can help improve data quality' Flat seismic events affected by NMO stretch shifting to lower frequencies = 'Post-imaging processing can correct amplitude distortion due to NMO stretch'
Match the seismic effect with its impact on data quality:
Reverberations or 'multiples' = Causes interference with the primary wavefield Tuning effects = Can cause interference with the primary wavefield Residual NMO = Distorts offset-dependent reflectivity NMO Stretch = Broadens the shape of the wavelet at further offsets
Match the seismic processing step with its purpose:
NMO Normal Moveout correction = Corrects reflection arrival times for amplitude analysis Migration or imaging = Corrects moveout and aligns events across a gather Residual Moveout correction = Addresses residual NMO effects Calculation of Intercept and Gradient = Quantifies the impact of residual NMO on AVO response
Match the seismic attribute with its impact on AVO analysis:
Residual NMO = Distorts AVO response and requires higher order corrections NMO Stretch = Broadens wavelet shape and affects near offsets more Fluid Factor = Indicates deviations from Castagna's Mudrock line for hydrocarbon zones AVO Sum (A+B) = Shows potential hydrocarbon indicators at top and base of reservoir
Match the physical effect in seismic processing with its impact on data quality:
Noise interference = Obscures desired primary signal amplitudes Acquisition related effects = Can cause interference due to source wavefield directivity Processing Noise attenuation techniques = Attenuate noise while preserving primary amplitudes Understanding distortions in offset-dependent reflectivity = Essential for successful AVO analysis
Match the seismic amplitude processing technique with its description:
NMO Normal Moveout correction = Corrects reflection arrival times for amplitude analysis Residual Moveout correction = Addresses residual NMO effects for accurate velocity analysis Calculation of Intercept and Gradient = Quantifies the impact of residual NMO on AVO response AVO Sum (A+B) = Shows potential hydrocarbon indicators at top and base of reservoir
Match the noise-related term with its description:
Noise interference with primary wavefield = Obscures desired signal amplitudes Noise attenuation techniques = Preserve primary amplitudes while reducing noise Acquisition noise issues = Related to source wavefield directivity or receiver orientation Processing noise removal = Efficiently removes noise while maintaining primary signal
Match the seismic data feature with its corresponding method for improvement:
Residual NMO correction = Improves AVO response by addressing velocity variations Migration or imaging step correction = Corrects moveout and aligns events for accurate imaging Calculation of Intercept and Gradient analysis = Quantifies impact of residual NMO on AVO attributes NMO Stretch correction = Reduces broadening of wavelets at far offsets
Match the physical effect in seismic processing with its impact on data quality:
Reverberations or 'multiples' = Causes interference with the primary wavefield Tuning effects = Can cause interference with the primary wavefield Residual NMO = Distorts offset-dependent reflectivity NMO Stretch = Broadens the shape of the wavelet at further offsets
Match the seismic processing step with its purpose:
NMO Normal Moveout correction = Corrects reflection arrival times for amplitude analysis Migration or imaging = Corrects moveout and aligns events across a gather Residual Moveout correction = Addresses residual NMO effects Calculation of Intercept and Gradient = Quantifies the impact of residual NMO on AVO response
Match the seismic attribute with its impact on AVO analysis:
Residual NMO = Distorts AVO response and requires higher order corrections NMO Stretch = Broadens wavelet shape and affects near offsets more Fluid Factor = Indicates deviations from Castagna's Mudrock line for hydrocarbon zones AVO Sum (A+B) = Shows potential hydrocarbon indicators at top and base of reservoir
Learn about the AVO Sum and AVO Difference concepts in geophysics, and how they can be utilized for prospect reconnaissance of Class 3 gas sands. Understand the significance of Scaled Poisson’s Ratio Change as a tool in geophysical exploration.
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