Errors in stacking velocity—True velocity conversion over complex geologic situations

Blackburn, G

doi:10.1190/1.1441043

Cited by 22 publications

(10 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…When we do not see this relationship, we tend to consider this as ‘error’ in the stacking velocity. The word ‘error’ appears in the title (Blackburn 1980) or in the text of papers. For example, ‘(i)n the presence of velocity anomalies, stacking velocities show systematic errors’ (Armstrong, McAteer and Connolly 2001, p. 81).…”

Section: Shallow Velocity Anomalies and Stacking Velocity ‘Errors’mentioning

confidence: 99%

Stacking velocities in the presence of overburden velocity anomalies

Blias¹

2009

Geophysical Prospecting

View full text Add to dashboard Cite

Lateral velocity changes (velocity anomalies) in the overburden may cause significant oscillations in normal moveout velocities. Explicit analytical moveout formulas are presented and provide a direct explanation of these lateral fluctuations and other phenomena for a subsurface with gentle deep structures and shallow overburden anomalies. The analytical conditions for this have been derived for a depth‐velocity model with gentle structures with dips not exceeding 12°. The influence of lateral interval velocity changes and curvilinear overburden velocity boundaries can be estimated and analysed using these formulas. An analytical approach to normal moveout velocity analysis in a laterally inhomogeneous medium provides an understanding of the connection between lateral interval velocity changes and normal moveout velocities. In the presence of uncorrected shallow velocity anomalies, the difference between root‐mean‐square and stacking velocity can be arbitrarily large to the extent of reversing the normal moveout function around normal incidence traveltimes. The main reason for anomalous stacking velocity behaviour is non‐linear lateral variations in the shallow overburden interval velocities or the velocity boundaries. A special technique has been developed to determine and remove shallow velocity anomaly effects. This technique includes automatic continuous velocity picking, an inversion method for the determination of shallow velocity anomalies, improving the depth‐velocity model by an optimization approach to traveltime inversion (layered reflection tomography) and shallow velocity anomaly replacement. Model and field data examples are used to illustrate this technique.

show abstract

Section: Shallow Velocity Anomalies and Stacking Velocity ‘Errors’mentioning

confidence: 99%

Stacking velocities in the presence of overburden velocity anomalies

Blias¹

2009

Geophysical Prospecting

View full text Add to dashboard Cite

show abstract

“…The use of stacking velocities for depth conversion has been discussed by Al‐Chalabi (1979) and Blackburn (1980). Such use of stacking velocities assumes that anisotropy has been compensated for because stacking velocities are biased towards the ‘horizontal component’ and it is the ‘vertical component’ (which is slower) that is needed for depth conversion.…”

Section: Effects Of Overburden Velocity Anomaliesmentioning

confidence: 99%

Removal of overburden velocity anomaly effects for depth conversion

Armstrong

McAteer²,

Connolly

2001

Geophysical Prospecting

View full text Add to dashboard Cite

A method of compensating for the presence of discrete overburden velocity anomalies during depth conversion of time horizons interpreted on conventional, post‐stack time‐migrated seismic data is presented. Positive and negative time delays are estimated either from the push‐down or pull‐up of reflectors directly beneath the anomalies or from interpreted time thickness of the anomalous body and interval velocities estimated from well data. The critical steps are pre‐stack simulation of seismic acquisition across the velocity anomalies, incorporating the effects of a Fresnel volume which changes its width as a function of depth, and simulation of common‐midpoint (CMP) stacking using a linear regression of time delay, Δt, versus offset‐squared, X2. The time‐correction method predicts the time distortion for any target horizon and the distortion is removed as a correction in time. Depth conversion is then performed using a background velocity function. The final average velocity map is calculated from the resulting depth structure and the raw times at the target horizon. The method is implemented by manipulating time grids within an industry‐standard mapping package. The final average velocity map shows steep lateral velocity gradients which are constrained by the interpreted boundaries of the velocity anomalies.

show abstract

“…1-2, the presence of r e f r a c t i o n and particularly d i f f r a c t i o n energy deteriorates the applicability of CMP velocity analysis techniques. This was also mentioned by Taner et al (1970) and later by Blackburn (1980). Arguing that downward wave field extrapolation focusses diffraction energy and thus diminishes its smearing effect, Doherty and Claerbout (1976) Gardner et al (1974) and Sattlegger (1975), and applied in practice by Dohr and Stiller (1975) and Sattlegger et al (1976).…”

Section: Velocity Analysis Techniques Concerning Reflection Energymentioning

confidence: 99%

“…As mentioned in the previous subsections, and more systematically analyzed by Taner et al (1970) and Blackburn (1980), CMP gathers loose their simple geometric properties when comprising an abundant amount of scattering d i ff r a c t i o n energy. Hence, for complex, laterally discontinuous structures, velocity analysis techniques based on the hyperbolic CMP concept are not applicable.…”

Section: Velocity Analysis Techniques Concerning Diffraction Datamentioning

confidence: 99%

Velocity analysis based on minimum entropy

Vries

1984

GEOPHYSICS

View full text Add to dashboard Cite

Seismic resolution is determined by the sparsity of reflection events together with the dispersion of the wavelets representing those events. In this paper, minimum entropy (ME) norms are introduced as a measure of spatial resolving power. It is shown that the lateral dispersion of inverted diffractor responses (inverted spatial wavelets) increases with increasing velocity error. Using this property, minimum entropy velocity analysis (MEVA) is proposed to extract velocity information from diffraction energy. MEVA can be successfully applied to zero‐offset (including poststack) data and common‐offset data with a sufficient amount of diffraction energy. In addition, MEVA can be used as an alternative to existing CMP velocity estimation techniques.

show abstract

Errors in stacking velocity—True velocity conversion over complex geologic situations

Cited by 22 publications

References 14 publications

Stacking velocities in the presence of overburden velocity anomalies

Stacking velocities in the presence of overburden velocity anomalies

Removal of overburden velocity anomaly effects for depth conversion

Velocity analysis based on minimum entropy

Contact Info

Product

Resources

About