Nonlinear pairwise alignment of seismic traces

Geophysics ◽  
2004 ◽  
Vol 69 (6) ◽  
pp. 1552-1559 ◽  
Author(s):  
Christopher L. Liner ◽  
Robert G. Clapp
Keyword(s):  
Seismic Data ◽  
Field Data ◽  
Pairwise Alignment ◽  
Optimization Method ◽  
Synthetic Seismograms ◽  
Amino Acid Sequences ◽  
Global Alignment ◽  
Global Optimization Method ◽  
S Wave ◽  
Alignment Problem

Seismic trace alignment is a recurring need in seismic processing and interpretation. For global alignment via static shift, there are robust tools available, including crosscorrelation. However, another kind of alignment problem arises in applications as diverse as associating synthetic seismograms to field data, harmonizing P‐ and S‐wave data, residual NMO, and final multilevel flattening of common image gathers. These cases require combinations of trace compression, extension, and shift—all of which are time variant. The difficulty is to find a mapping between the traces that is in some senseoptimum. This problem is solved here using a modified form of the Needleman‐Wunsch algorithm, a global optimization method originally developed for aligning amino acid sequences in proteins. Applied to seismic traces, this algorithm provides a nonlinear mapping of one seismic trace onto another. The method extends to multitrace alignment since that problem can be broken down into a cascade of pairwise alignments. Seismic implementation of the Needleman‐Wunsch algorithm is a promising new tool for nonlinear alignment and flattening of seismic data.

scholarly journals High-resolution coherency functionals for velocity analysis: An application for subbasalt seismic exploration

Geophysics ◽  
2013 ◽  
Vol 78 (5) ◽  
pp. U53-U63 ◽  
Author(s):  
Andrea Tognarelli ◽  
Eusebio Stucchi ◽  
Alessia Ravasio ◽  
Alfredo Mazzotti
Keyword(s):  
High Resolution ◽  
Seismic Data ◽  
Field Data ◽  
Signal To Noise Ratio ◽  
Synthetic Seismograms ◽  
Seismic Exploration ◽  
Velocity Analysis ◽  
Signal To Noise ◽  
Geologic Setting ◽  
Analytic Signals

We tested the properties of three different coherency functionals for the velocity analysis of seismic data relative to subbasalt exploration. We evaluated the performance of the standard semblance algorithm and two high-resolution coherency functionals based on the use of analytic signals and of the covariance estimation along hyperbolic traveltime trajectories. Approximate knowledge of the wavelet was exploited to design appropriate filters that matched the primary reflections, thereby further improving the ability of the functionals to highlight the events of interest. The tests were carried out on two synthetic seismograms computed on models reproducing the geologic setting of basaltic intrusions and on common midpoint gathers from a 3D survey. Synthetic and field data had a very low signal-to-noise ratio, strong multiple contamination, and weak primary subbasalt signals. The results revealed that high-resolution coherency functionals were more suitable than semblance algorithms to detect primary signals and to distinguish them from multiples and other interfering events. This early discrimination between primaries and multiples could help to target specific signal enhancement and demultiple operations.

Full‐waveform processing and interpretation of kilohertz cross‐well seismic data

Geophysics ◽  
1993 ◽  
Vol 58 (9) ◽  
pp. 1248-1256 ◽  
Author(s):  
Ashraf A. Khalil ◽  
Robert R. Stewart ◽  
David C. Henley
Keyword(s):  
Oil Recovery ◽  
Seismic Data ◽  
Shear Waves ◽  
Synthetic Seismograms ◽  
Oil Field ◽  
S Wave ◽  
Sonic Log ◽  
The Cross ◽  
Interval Velocities ◽  
The Individual

High‐frequency, cross‐well seismic data, from the Midale oil field of southeastern Saskatchewan, are analyzed for direct and reflected energy. The goal of the analysis is to produce interpretable sections to assist in enhanced oil recovery activities ([Formula: see text] injection) in this field. Direct arrivals are used for velocity information while reflected arrivals are processed into a reflection image. Raw field data show a complex assortment of wave types that includes direct compressional and shear waves and reflected shear waves. A traveltime inversion technique (layer stripping via ray tracing) is used to obtain P‐ and S‐wave interval velocities from the respective direct arrivals. The velocities from the cross‐well inversion and the sonic log are in reasonable agreement. The subsurface coverage of the cross‐well geometry is investigated; it covers zones extending from the source well to the receiver well and includes regions above and below the source/receiver depths. Upgoing and downgoing primary reflections are processed, in a manner similar to the vertical seismic profiling/common‐depth‐point (VSP/CDP) map, to construct the cross‐well images. A final section is produced by summing the individual reflection images from each receiver‐gather map. This section provides an image with evidence of strata thicknesses down to about 1 m. Synthetic seismograms are used to interpret the final sections. Correlations can be drawn between some of the events on the synthetic seismograms and the cross‐well image.

APPARENT ATTENUATION DUE TO INTRABED MULTIPLES, II

Geophysics ◽  
1978 ◽  
Vol 43 (4) ◽  
pp. 730-737 ◽  
Author(s):  
M. Schoenberger ◽  
F. K. Levin
Keyword(s):  
Seismic Data ◽  
Field Data ◽  
Seismic Waves ◽  
Synthetic Seismograms ◽  
Frequency Dependent ◽  
Total Attenuation ◽  
The World ◽  
Apparent Attenuation

In a paper with the same title published in Geophysics (June 1974), we showed that synthetic seismograms from two wells gave a frequency‐dependent attenuation due to intrabed multiples of about 0.06 dB/wavelength. This loss was 1/3 to 1/2 of the total attenuation found for field data on lines near the wells. Our data sufficed to confirm the conclusion of O’Doherty and Anstey that attenuation caused by intrabed multiples may be appreciable, but the number of wells was insufficient to establish the magnitude of that attenuation in general. To get a better feel for intrabed multiple‐generated attenuation, we have computed losses for 31 additional wells from basins all over the world. Sonic and, where available, density logs were digitized every foot and converted into synthetic seismograms with 50 orders of intrabed multiples. Using the technique of the 1974 paper of extending the logs and placing an isolated reflector 2000 ft below the bottom of the wells, we computed attenuation constants for plane seismic waves that had traveled down and back through the subsurfaces defined by the logs. Computed constants varied from 0.01 dB/wavelength to 0.22 dB/wavelength. Total traveltimes ranged from 0.7 to 2.7 sec; the average was 1.9 sec. Attenuation constants computed from surface seismic data near four of the 31 wells gave values 1.3 to 7 times the corresponding intrabed constants. Thus, attenuation due to intrabed multiples accounts for an appreciable fraction of the observed attenuation but by no means all of it.

Source-side spatial wavefield gradients in land seismic exploration

Geophysics ◽  
2019 ◽  
Vol 84 (5) ◽  
pp. P73-P85 ◽  
Author(s):  
Cédéric Van Renterghem ◽  
Cédric Schmelzbach ◽  
David Sollberger ◽  
Mauro Häusler ◽  
Johan Olof Anders Robertsson
Keyword(s):  
Seismic Data ◽  
Field Data ◽  
Seismic Exploration ◽  
Gradient Estimates ◽  
Spatial Gradient ◽  
Receiver Side ◽  
S Wave ◽  
Wave Source ◽  
Rotational Components ◽  
Gradient Based

The recording of seismic data using arrays of densely spaced receivers enables the estimation of the spatial gradient components of the wavefield, in addition to the acquisition of conventional translational motion. We have extended the concept of array-based receiver-side gradiometry to the source-side and investigated the potential of combining source- and receiver-side gradient estimates for land seismic exploration. The robustness of array-based gradient source formation is demonstrated with a field data reciprocity experiment. We apply a gradient-based elastic wavefield decomposition technique to small arrays of densely spaced vertically and horizontally oriented force sources and determine with synthetic and field data examples that the processing of data obtained from multicomponent source arrays allows us to simulate a composite source that theoretically only emits S-waves at all emergence angles. A promising application of the gradient-based S-wave source is downhole S-wave imaging. Finally, by combining source- and receiver-side gradient estimates, 49C seismic data can be obtained comprising three translational components, three rotational components, and one divergence component on the source and receiver side. This concept could have a significant potential to enhance the acquisition and processing of data from locally dense arrays in land seismic exploration.

A case study showing the value of multioffset synthetic seismograms in seismic data interpretation

2016 ◽  
Vol 4 (4) ◽  
pp. T455-T459 ◽  
Author(s):  
J. Helen Isaac ◽  
Don C. Lawton
Keyword(s):  
Seismic Data ◽  
Upper Cretaceous ◽  
Normal Incidence ◽  
High Amplitude ◽  
Synthetic Seismogram ◽  
Synthetic Seismograms ◽  
Seismic Survey ◽  
Research Station ◽  
S Wave ◽  
Low Amplitude

A baseline 3D3C seismic survey was acquired in May 2014 at a Field Research Station in Southern Alberta, Canada, which is the site of experimental [Formula: see text] injection into an Upper Cretaceous sandstone at approximately 300 m depth. We have created synthetic seismograms from sonic and density logs to identify reflectors seen on the processed seismic data. The high-amplitude positive response (peak) at the top of the Upper Cretaceous Milk River Formation sandstone on the normal incidence PP synthetic seismogram does not match the response seen on the migrated PP seismic data, which is a very low amplitude peak. For such a high impedance, low Poisson’s ratio sandstone, the Zoeppritz equations predict a high-amplitude reflection coefficient at zero offset, then a decrease in amplitude, and even a change in polarity with increasing source-receiver offset. To match the stacked seismic data better, we have created offset synthetic seismograms using P- and S-wave sonic logs and density logs. The character of the top Milk River reflection on the seismic data stacked using all offset traces resembles that observed on the stacked offset synthetic seismogram, which is a similar low-amplitude peak. The character of the top Milk River reflection on the seismic data stacked using only near-offset traces to 250 m looks like that seen on the normal incidence synthetic seismogram.

Practical aspects of an elastic migration/inversion of crosshole data for reservoir characterization: A Paris basin example

Geophysics ◽  
1989 ◽  
Vol 54 (12) ◽  
pp. 1587-1595 ◽  
Author(s):  
W. B. Beydoun ◽  
J. Delvaux ◽  
M. Mendes ◽  
G. Noual ◽  
A. Tarantola
Keyword(s):  
Seismic Data ◽  
Field Data ◽  
Reservoir Characterization ◽  
Residual Energy ◽  
Paris Basin ◽  
S Wave ◽  
Depth Level ◽  
Surface Reflection ◽  
Depth Images ◽  
And Migration

The main obstacle for a detailed study of a reservoir is the lack of geophysical and petrophysical information between producing wells. Crosshole seismic data can aid reservoir geologists and engineers in (1) estimating the volume of oil in place, (2) mapping permeability/porosity barriers, and ultimately (3) monitoring and designing enhanced off‐recovery experiments. Due to their high‐frequency content, crosshole seismic data offer an ideal information link between conventional seismic data (surface reflection, VSPs, etc.) and full‐waveform sonic acoustic logs. Using a weightdrop downhole source located at one depth level, acoustic and multicomponent data at two different wells were collected in the Paris basin with interwell distances of about 100 m. The target zone includes three sand reservoir levels between depths of 575 and 600 m. A 2‐D elastic migration/inversion (M/I) of the scattered S‐S and S‐P crosshole field data produced high‐resolution S‐wave velocity and density depth images of the subsurface, extending information away from wells and identifying reservoirs. The residual energy reduction between synthetic seismograms derived from M/I images and field data is 18 percent, confirming that images contain elastic information. Structural dips obtained are very reasonable, the observed vertical spatial resolution being of the order of 3 m. We believe that this is the first time that such techniques have been applied to crosshole data. Elastic M/I images are generally better than elastic VSP‐CDP and migration images and have the advantage of producing global quality measures of images. Such a technique uses as input a background velocity, e.g., a tomogram obtained by traveltime tomography, and complements the background by recovering subsurface discontinuities and changes in elastic parameters within the signal bandwidth.

Geometrical spreading in a layered transversely isotropic medium with vertical symmetry axis

Geophysics ◽  
2003 ◽  
Vol 68 (6) ◽  
pp. 2082-2091 ◽  
Author(s):  
Bjørn Ursin ◽  
Ketil Hokstad
Keyword(s):  
Ray Tracing ◽  
Seismic Data ◽  
Symmetry Axis ◽  
Transversely Isotropic ◽  
Analytical Approximation ◽  
Geometrical Spreading ◽  
S Wave ◽  
Weak Anisotropy ◽  
P Waves ◽  
Amplitude Versus

Compensation for geometrical spreading is important in prestack Kirchhoff migration and in amplitude versus offset/amplitude versus angle (AVO/AVA) analysis of seismic data. We present equations for the relative geometrical spreading of reflected and transmitted P‐ and S‐wave in horizontally layered transversely isotropic media with vertical symmetry axis (VTI). We show that relatively simple expressions are obtained when the geometrical spreading is expressed in terms of group velocities. In weakly anisotropic media, we obtain simple expressions also in terms of phase velocities. Also, we derive analytical equations for geometrical spreading based on the nonhyperbolic traveltime formula of Tsvankin and Thomsen, such that the geometrical spreading can be expressed in terms of the parameters used in time processing of seismic data. Comparison with numerical ray tracing demonstrates that the weak anisotropy approximation to geometrical spreading is accurate for P‐waves. It is less accurate for SV‐waves, but has qualitatively the correct form. For P waves, the nonhyperbolic equation for geometrical spreading compares favorably with ray‐tracing results for offset‐depth ratios less than five. For SV‐waves, the analytical approximation is accurate only at small offsets, and breaks down at offset‐depth ratios less than unity. The numerical results are in agreement with the range of validity for the nonhyperbolic traveltime equations.

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