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Questions and Answers
Which method is commonly used to remove noise from seismic data?
What is the formula used to estimate dipping layers?
What are DHIs?
What is the method used to correct for the different travel times of reflected events for different geophone positions?
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What is the process used to move reflections back to their point of origin and restore seismic reflectors to their proper x-y position?
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What is the method used to further remove noise from seismic traces and increase vertical resolution?
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What are the three types of DHIs mentioned in the text?
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What is the process used to improve data/image quality in seismic surveying?
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What is AVO analysis used for?
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Which method is commonly used to remove noise from seismic data?
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What is the formula used to estimate dipping layers?
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What are DHIs?
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What is the method used to correct for the different travel times of reflected events for different geophone positions?
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What is the process used to move reflections back to their point of origin and restore seismic reflectors to their proper x-y position?
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What is the method used to further remove noise from seismic traces and increase vertical resolution?
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What are the three types of DHIs mentioned in the text?
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What is the process used to improve data/image quality in seismic surveying?
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What is AVO analysis used for?
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Which method is commonly used to remove noise from seismic data?
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What is the purpose of stacking seismic traces?
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What is the fold in CMP stacking determined by?
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What is the purpose of deconvolution in seismic reflection processing?
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What is the formula for estimating dipping layers?
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What are DHIs in seismic surveying?
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What is the purpose of AVO analysis in seismic surveying?
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What are the two parameters used to quantify AVO response?
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How can DHIs be used to map the extent of gas-filled reservoirs?
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Seismic data is never contaminated by noise.
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Frequency domain filters are not commonly used to remove noise from seismic data.
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Stacking seismic traces is a method used to increase random noise.
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CMP stacking can only be vertical, not horizontal.
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Reflectivity and convolution do not affect the seismic trace recorded in the field.
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Determining dip angle θ requires solving for travel time values from different geophone positions and distances.
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NMO correction is not used to correct for the different travel times of reflected events for different geophone positions.
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Migration is used to move reflections back to their point of origin and restore seismic reflectors to their proper x-y position.
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Oil sands have higher impedance than water sands and shales.
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Study Notes
Seismic Reflection Processing
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Filtering data is a common method used to remove noise and enhance the vertical resolution of seismic data.
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Seismic data is often contaminated by noise from various sources, including wind, traffic, and cultural noise, electrical signals, ocean waves, and motion.
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Frequency domain filters, such as high pass, low pass, band pass, and notch filters, are commonly used to remove noise from seismic data.
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Stacking seismic traces is another method used to reduce random noise and increase the signal-to-noise ratio.
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Common-mid(depth)-point (CMP) stacking is a method of summing signals from similar input channels to improve the signal-to-noise ratio.
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CMP stacking can be vertical or horizontal, with the fold (number of times the same point on a reflector is sampled) determined by the number of geophones and array spacing.
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Reflectivity and convolution are two factors that determine the seismic trace recorded in the field.
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Deconvolution (inverse filtering) is a method used to further remove noise from seismic traces and increase vertical resolution.
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Travel time curve is a hyperbola, but asymmetric where the axial plane is at x = -2hsinθ.
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Determining dip angle θ requires solving for travel time values from different geophone positions and distances.
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NMO correction is a method used to correct for the different travel times of reflected events for different geophone positions.
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Migration is a process used to move reflections back to their point of origin and restore seismic reflectors to their proper x-y position.Introduction to Seismic Surveying and Direct Hydrocarbon Indicators (DHIs)
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Dipping layers can be estimated using the formula Δtd = t2 - t1 ~ to (s sinθ /h) ~ 2s sinθ /V, where Δtd is dip moveout, s is distance, h is thickness, and θ is dip angle.
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Seismic surveying involves pre-migration, migrated stack, and seismic migration techniques to improve data/image quality.
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Seismic interpretation involves working from the top of the section towards the bottom to distinguish major reflectors and geometries of seismic sequences.
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DHIs (Direct Hydrocarbon Indicators) are anomalous seismic responses related to the presence of hydrocarbons, caused by the acoustic impedance of porous rock decreasing as hydrocarbon replaces brine in pore spaces.
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DHIs include amplitude anomaly, fluid contact reflection, and fit to structural contours.
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Oil sands have lower impedance than water sands and shales, and gas sands have lower impedance than oil sands.
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The larger the impedance difference between the HC sand and its encasing shale, the greater the anomaly.
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DHIs can be detected through techniques such as Amplitude Variation with Offset (AVO), which uses pre-stack seismic data to determine thickness, porosity, density, velocity, lithology, and fluid content of rocks.
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AVO analysis helps unravel lithology and fluid effects, especially at the top of a reservoir, by examining variations in amplitude with angle or offset.
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Maps or crossplots of AVO responses can be used to detect pore-fill anomalies, i.e. hydrocarbons, and map their lateral extent.
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AVO response is quantified in terms of two parameters: intercept (A) and slope (B).
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Seismic data can be used to estimate A and B, and to map the extent of gas-filled reservoirs using DHIs.
Seismic Reflection Processing
-
Filtering data is a common method used to remove noise and enhance the vertical resolution of seismic data.
-
Seismic data is often contaminated by noise from various sources, including wind, traffic, and cultural noise, electrical signals, ocean waves, and motion.
-
Frequency domain filters, such as high pass, low pass, band pass, and notch filters, are commonly used to remove noise from seismic data.
-
Stacking seismic traces is another method used to reduce random noise and increase the signal-to-noise ratio.
-
Common-mid(depth)-point (CMP) stacking is a method of summing signals from similar input channels to improve the signal-to-noise ratio.
-
CMP stacking can be vertical or horizontal, with the fold (number of times the same point on a reflector is sampled) determined by the number of geophones and array spacing.
-
Reflectivity and convolution are two factors that determine the seismic trace recorded in the field.
-
Deconvolution (inverse filtering) is a method used to further remove noise from seismic traces and increase vertical resolution.
-
Travel time curve is a hyperbola, but asymmetric where the axial plane is at x = -2hsinθ.
-
Determining dip angle θ requires solving for travel time values from different geophone positions and distances.
-
NMO correction is a method used to correct for the different travel times of reflected events for different geophone positions.
-
Migration is a process used to move reflections back to their point of origin and restore seismic reflectors to their proper x-y position.Introduction to Seismic Surveying and Direct Hydrocarbon Indicators (DHIs)
-
Dipping layers can be estimated using the formula Δtd = t2 - t1 ~ to (s sinθ /h) ~ 2s sinθ /V, where Δtd is dip moveout, s is distance, h is thickness, and θ is dip angle.
-
Seismic surveying involves pre-migration, migrated stack, and seismic migration techniques to improve data/image quality.
-
Seismic interpretation involves working from the top of the section towards the bottom to distinguish major reflectors and geometries of seismic sequences.
-
DHIs (Direct Hydrocarbon Indicators) are anomalous seismic responses related to the presence of hydrocarbons, caused by the acoustic impedance of porous rock decreasing as hydrocarbon replaces brine in pore spaces.
-
DHIs include amplitude anomaly, fluid contact reflection, and fit to structural contours.
-
Oil sands have lower impedance than water sands and shales, and gas sands have lower impedance than oil sands.
-
The larger the impedance difference between the HC sand and its encasing shale, the greater the anomaly.
-
DHIs can be detected through techniques such as Amplitude Variation with Offset (AVO), which uses pre-stack seismic data to determine thickness, porosity, density, velocity, lithology, and fluid content of rocks.
-
AVO analysis helps unravel lithology and fluid effects, especially at the top of a reservoir, by examining variations in amplitude with angle or offset.
-
Maps or crossplots of AVO responses can be used to detect pore-fill anomalies, i.e. hydrocarbons, and map their lateral extent.
-
AVO response is quantified in terms of two parameters: intercept (A) and slope (B).
-
Seismic data can be used to estimate A and B, and to map the extent of gas-filled reservoirs using DHIs.
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Test your knowledge on Seismic Reflection Processing and Direct Hydrocarbon Indicators (DHIs) with this quiz! Learn about common methods used to remove noise and enhance vertical resolution of seismic data, including frequency domain filters and stacking seismic traces. Explore the process of seismic surveying, interpretation, and migration to improve data quality. Discover the different types of DHIs, including amplitude anomaly, fluid contact reflection, and fit to structural contours, and how they can be detected through techniques such as Amplitude Variation with
