Separation of signal and coherent noise by migration filtering

Geophysics ◽  
2000 ◽  
Vol 65 (2) ◽  
pp. 574-583 ◽  
Author(s):  
Tamas Nemeth ◽  
Hongchuan Sun ◽  
Gerard T. Schuster
Keyword(s):  
Forward Modeling ◽  
P Wave ◽  
Wave Reflections ◽  
S Wave ◽  
Coherent Noise ◽  
Signal Model ◽  
Model Estimate ◽  
Wavefield Separation ◽  
Order Of Magnitude ◽  
Magnitude Increase

A key issue in wavefield separation is to find a domain where the signal and coherent noise are well separated from one another. A new wavefield separation algorithm, called migration filtering, separates data arrivals according to their path of propagation and their actual moveout characteristics. This is accomplished by using forward modeling operators to compute the signal and the coherent noise arrivals. A linearized least‐squares inversion scheme yields model estimates for both components; the predicted signal component is constructed by forward modeling the signal model estimate. Synthetic and field data examples demonstrate that migration filtering improves separation of P-wave reflections and surface waves, P-wave reflections and tube waves, P-wave diffractions, and S-wave diffractions. The main benefits of the migration filtering method compared to conventional filtering methods are better wavefield separation capability, the capability of mixing any two conventional transforms for wavefield separation under a general inversion framework, and the capability of mitigating the signal and coherent noise crosstalk by using regularization. The limitations of the method may include more than an order of magnitude increase in computation costs compared to conventional transforms and the difficulty of selecting the proper modeling operators for some wave modes.

Wavefield separation by 3-D filtering in crosshole seismic reflection processing

Geophysics ◽  
1994 ◽  
Vol 59 (7) ◽  
pp. 1065-1071 ◽  
Author(s):  
Peter S. Rowbotham ◽  
Neil R. Goulty
Keyword(s):  
Seismic Reflection ◽  
Primary Energy ◽  
P Wave ◽  
Head Wave ◽  
Common Source ◽  
S Wave ◽  
Coherent Noise ◽  
Data Set ◽  
Seismic Reflection Data ◽  
Wavefield Separation

In processing crosshole seismic reflection data, it is necessary to separate the upgoing and downgoing primary reflections from each other, from the direct waves, and from other wave types in the data. We have implemented a 3-D f-k-k filter for wavefield separation that is applied in a single pass. The complete data set is treated as a data volume, with each sample defined by the three coordinates of source depth, receiver depth, and time. The filter works well because upgoing primaries, downgoing primaries, and direct waves lie in different quadrants in f-k-k space. The strongest multiples, including mode‐converted multiples, lie in the same quadrants in f-k-k space as the direct waves, so they are readily rejected together. Tube waves and mode‐converted primaries are also suppressed as most of the energy in these wave types lies outside the pass volume for P‐wave primaries. Some head wave and S‐wave primary energy will be passed by the filter; however, these waves tend to have low amplitudes and late arrival times, respectively, and will be smeared out on imaging with the P‐wave velocity field. We have processed a real crosshole data set using two different methods of wavefield separation: applying 2-D f-k filtering to common source gathers and applying a 3-D f-k-k filter to the whole data set. The migrated image produced after 3-D f-k-k filtering contains less coherent noise and consequently shows improved continuity of reflectors.

P-wave and S-wave azimuthal anisotropy at a naturally fractured gas reservoir, Bluebell‐Altamont Field, Utah

Geophysics ◽  
1999 ◽  
Vol 64 (4) ◽  
pp. 1312-1328 ◽  
Author(s):  
Heloise B. Lynn ◽  
Wallace E. Beckham ◽  
K. Michele Simon ◽  
C. Richard Bates ◽  
M. Layman ◽  
...  
Keyword(s):  
Azimuthal Anisotropy ◽  
P Wave ◽  
Fracture Density ◽  
Wave Reflections ◽  
S Wave ◽  
Gas Reservoir ◽  
Green River ◽  
Wave Data ◽  
Reflection Data ◽  
Naturally Fractured

Reflection P- and S-wave data were used in an investigation to determine the relative merits and strengths of these two data sets to characterize a naturally fractured gas reservoir in the Tertiary Upper Green River formation. The objective is to evaluate the viability of P-wave seismic to detect the presence of gas‐filled fractures, estimate fracture density and orientation, and compare the results with estimates obtained from the S-wave data. The P-wave response to vertical fractures must be evaluated at different source‐receiver azimuths (travelpaths) relative to fracture strike. Two perpendicular lines of multicomponent reflection data were acquired approximately parallel and normal to the dominant strike of Upper Green River fractures as obtained from outcrop, core analysis, and borehole image logs. The P-wave amplitude response is extracted from prestack amplitude variation with offset (AVO) analysis, which is compared to isotropic‐model AVO responses of gas sand versus brine sand in the Upper Green River. A nine‐component vertical seismic profile (VSP) was also obtained for calibration of S-wave reflections with P-wave reflections, and support of reflection S-wave results. The direction of the fast (S1) shear‐wave component from the reflection data and the VSP coincides with the northwest orientation of Upper Green River fractures, and the direction of maximum horizontal in‐situ stress as determined from borehole ellipticity logs. Significant differences were observed in the P-wave AVO gradient measured parallel and perpendicular to the orientation of Upper Green River fractures. Positive AVO gradients were associated with gas‐producing fractured intervals for propagation normal to fractures. AVO gradients measured normal to fractures at known waterwet zones were near zero or negative. A proportional relationship was observed between the azimuthal variation of the P-wave AVO gradient as measured at the tops of fractured intervals, and the fractional difference between the vertical traveltimes of split S-waves (the “S-wave anisotropy”) of the intervals.

Detection of near-surface hydrocarbon seeps using P- and S-wave reflections

2016 ◽  
Vol 4 (3) ◽  
pp. SH21-SH37 ◽  
Author(s):  
Mathieu J. Duchesne ◽  
André J.-M. Pugin ◽  
Gabriel Fabien-Ouellet ◽  
Mathieu Sauvageau
Keyword(s):  
P Wave ◽  
Unconsolidated Sediments ◽  
Fluid Migration ◽  
Wave Reflections ◽  
S Wave ◽  
Abrupt Decrease ◽  
Seismic Reflection Data ◽  
Near Surface ◽  
Wave Data ◽  
Hydrocarbon Seeps

The combined use of P- and S-wave seismic reflection data is appealing for providing insights into active petroleum systems because P-waves are sensitive to fluids and S-waves are not. The method presented herein relies on the simultaneous acquisition of P- and S-wave data using a vibratory source operated in the inline horizontal mode. The combined analysis of P- and S-wave reflections is tested on two potential hydrocarbon seeps located in a prospective area of the St. Lawrence Lowlands in Eastern Canada. For both sites, P-wave data indicate local changes in the reflection amplitude and slow velocities, whereas S-wave data present an anomalous amplitude at one site. Differences between P- and S-wave reflection morphology and amplitude and the abrupt decrease in P-velocity are indirect lines of evidence for hydrocarbon migration toward the surface through unconsolidated sediments. Surface-gas analysis made on samples taken at one potential seeping site reveals the occurrence of thermogenic gas that presumably vents from the underlying fractured Utica Shale forming the top of the bedrock. The 3C shear data suggest that fluid migration locally disturbs the elastic properties of the matrix. The comparative analysis of P- and S-wave data along with 3C recordings makes this method not only attractive for the remote detection of shallow hydrocarbons but also for the exploration of how fluid migration impacts unconsolidated geologic media.

Separation of S‐wave and P‐wave reflections offshore western Florida

Geophysics ◽  
1984 ◽  
Vol 49 (5) ◽  
pp. 493-508 ◽  
Author(s):  
Robert H. Tatham ◽  
Donald V. Goolsbee
Keyword(s):  
Mode Conversion ◽  
Hard Water ◽  
P Wave ◽  
Angle Of Incidence ◽  
Wave Reflections ◽  
S Wave ◽  
Seismic Reflection Data ◽  
Reflection Time ◽  
Processing Techniques ◽  
Independent Confirmation

Hard water‐bottom marine environments, such as offshore western Florida, have presented particular problems in the acquisition and processing of seismic reflection data. One problem has been the limited angle of incidence (less than critical) available to P‐wave penetration into the subsurface. Mode conversion from P‐wave to S‐waves (SV), however, is quite efficient over a broad range of angles of incidence. After the success of a previously reported physical model experiment, an experimental line was acquired offshore western Florida. The 19 mile line, located approximately 100 miles west of Key West, Florida, was shot and processed. Three key factors have contributed to the successful recording of mode‐converted S‐wave reflections: (1) recognition of the effect of the group length on attenuation of energy arriving at large angles of incidence; (2) tau‐p processing techniques that allow separation of energy by angle of incidence; and (3) velocity filtering over a range of hyperbolic normal‐moveout (NMO) velocities as part of the forward tau‐p transform. These three factors, two of them data processing techniques, have allowed separation of P‐ and S‐wave energy in the marine environment. Overall, S‐wave reflections have been unambiguously identified to a reflection time of 2 sec and may be interpreted to a reflection time of 2 sec. Integrating an S‐wave section with P‐wave interpretations of offshore Florida data allows an independent confirmation of structural events. This independent confirmation may be more significant than improvements in the P‐wave data quality alone. Lateraly stable [Formula: see text] values are computed in intervals 1500 to 5000 ft thick and to S‐wave reflection times as great as 3 sec. The opportunity of [Formula: see text], interpretations for lithologic identification, gas thickness estimates, and general stratigraphic trap exploration makes mode‐converted shear waves a new tool in this area.

Modeling sensitivity of 3D, 9-C wide azimuth data to changes in fluid content and crack density in cracked reservoirs

Geophysics ◽  
2010 ◽  
Vol 75 (5) ◽  
pp. T155-T165 ◽  
Author(s):  
Herurisa Rusmanugroho ◽  
George A. McMechan
Keyword(s):  
Practical Importance ◽  
Crack Density ◽  
Maximum Amplitude ◽  
P Wave ◽  
Staggered Grid ◽  
Wave Reflections ◽  
S Wave ◽  
Reservoir Properties ◽  
Fluid Content ◽  
Isotropic Media

The volume density of cracks and the fluids contained in them are salient aspects of characterization of cracked reservoirs. Thus, it is of practical importance to investigate whether variations in these reservoir properties are detectable in seismic observations. Eighth-order staggered-grid, 3D finite-difference simulations generate nine-component amplitude variations with offset and azimuth (AVOAZ) for reflections from the top of a vertically cracked zone embedded in an isotropic host. The T-matrix method is used to calculate elastic stiffness tensors. Responses for various crack densities and fluid contents show sensitivity to the spatial orientation of, and variation in, anisotropy. In isotropic media, when source and receiver components have the same orientation (such as XX and YY), reflection amplitude contours align approximately perpendicular to the particle motion. Mixed components (such as XY and YX) have amplitude patterns thatare symmetrical pairs of the same, or opposite, polarity on either side of the diagonal of the 9-C response matrix. In anisotropic media, AVOAZ data show the same basic patterns and symmetries as for isotropic media but with a superimposed tendency for alignment parallel to the strike of the vertical cracks. The data contain combined effects related to the source, receiver, and crack orientations. The sensitivity of data to changes in fluid content is quantified by comparing the differences between responses to various fluid conditions, to the maximum amplitude of oil-filled crack responses. For a crack density of 0.1, amplitude differences are [Formula: see text] for oil-dry and [Formula: see text] for oil-brine. The corresponding values for S-wave reflections are [Formula: see text] for oil-dry and [Formula: see text] for oil-brine. Amplitude changes caused by changing the oil-filled crack density from 0.1 to 0.2 are [Formula: see text] for P-wave reflections and [Formula: see text] for S-wave reflections. These differences are visible in AVOAZ data and are potentially diagnostic for reservoir characterization.

VECTOR WAVEFIELD-SEPARATION TECHNIQUES FOR IMPROVED MULTI-COMPONENT SEISMIC EXPLORATION

2002 ◽  
Vol 42 (1) ◽  
pp. 613
Author(s):  
N. Hendrick ◽  
S. Hearn
Keyword(s):  
Vertical Component ◽  
P Wave ◽  
Seismic Exploration ◽  
Ocean Bottom ◽  
Production Environment ◽  
S Wave ◽  
Reflection Data ◽  
Wavefield Separation ◽  
Polarisation Analysis ◽  
Vector Separation

Analysis of multi-component seismic data commonly involves scalar processing of the vertical component to provide a conventional P-wave image, and scalar processing of the horizontal component(s) to yield an Swave image. A number of convincing examples now exist where such S-wave imagery has significantly enhanced hydrocarbon exploration.There is potential to achieve cleaner P- and S-wave images by more fully exploiting the true vector nature of multi-component reflection data. The simplest form of vector analysis, termed polarisation analysis, allows identification of different wave types. It does not, however, generally lead to effective wavefield separation, due to significant interference between the different waves in a typical exploration-seismic recording.More effective vector separation is possible if the particle-motion information from polarisation analysis is coupled with the more familiar tools of frequency and velocity filtering. Three related separation algorithms, termed MUSIC, IWSA and PIM are considered here. These techniques all utilise a parametric approach whereby wavefield slowness and polarisation are modelled simultaneously in the frequency domain.Synthetic and ocean-bottom cable examples are used to demonstrate practical issues relating to the use of these tools. The PIM algorithm is considered to be the most generally useful of the three multi-component wavefield separation algorithms. Implementation of these tools in a highly automated production environment is considered non-trivial. Hence, it is envisaged that such vector separation schemes will have most application for specialised data processing over identified target zones. Vector wavefield separation has the potential to amplify the considerable success already achieved with integrated P- and S-wave exploration.

Multicomponent VP/VS correlation analysis

Geophysics ◽  
1996 ◽  
Vol 61 (4) ◽  
pp. 1137-1149 ◽  
Author(s):  
James E. Gaiser
Keyword(s):  
Correlation Analysis ◽  
Wave Velocity ◽  
Seismic Profile ◽  
P Wave ◽  
Rock Properties ◽  
Wave Reflections ◽  
S Wave ◽  
Long Wavelength ◽  
Amplitude Inversion ◽  
P Wave Velocity

An important step in the simultaneous interpretation or inversion of multicomponent data sets is to quantitatively estimate the ratio of P‐wave velocity to S‐wave velocity [Formula: see text]. In this endeavor, I have developed correlation techniques to determine long‐wavelength components of [Formula: see text] that can lead to more accurate measurements of rock properties and processing parameters. P‐wave reflections are correlated with converted P‐ to S‐wave reflections (or S‐wave reflections) from the same location to determine which events are related to the same subsurface impedance contrasts. Shear waves are transformed (compressed) to P‐wave time via average [Formula: see text] conjugate operators before correlation. Aided by conventional P‐wave velocity information and petrophysical relationships, this technique provides optimal [Formula: see text] estimates in a similar manner that semblance analyses provide stacking velocities. These estimates can be used to transform the entire S‐wave trace to P‐wave time for short‐wavelength amplitude inversion. Also, a target‐oriented correlation analysis quantitatively determines interval [Formula: see text] at a specific horizon or group of horizons. Data from vertical seismic profile (VSP) stacked traces are used to evaluate these techniques. Long‐wavelength average and interval [Formula: see text] estimates obtained from the correlation analyses agree closely with [Formula: see text] results determined from VSP direct‐arrival traveltimes.

A hierarchical elastic full-waveform inversion scheme based on wavefield separation and the multistep-length approach

Geophysics ◽  
2016 ◽  
Vol 81 (3) ◽  
pp. R99-R123 ◽  
Author(s):  
Zhiming Ren ◽  
Yang Liu
Keyword(s):  
Wave Velocity ◽  
Waveform Inversion ◽  
P Wave ◽  
Model Parameters ◽  
Full Waveform Inversion ◽  
S Wave ◽  
Wave Velocities ◽  
Full Waveform ◽  
Wavefield Separation ◽  
P Wave Velocity

Elastic full-waveform inversion (FWI) updates model parameters by minimizing the residuals of the P- and S-wavefields, resulting in more local minima and serious nonlinearity. In addition, the coupling of different parameters degrades the inversion results. To address these problems, we have developed a hierarchical elastic FWI scheme based on wavefield separation and a multistep-length gradient approach. First, we have derived the gradients expressed by different wave modes; analyzed the crosstalk between various parameters; and evaluated the sensitivity of separated P-wave, separated S-wave, and P- and S-wave misfit functions. Then, a practical four-stage inversion workflow was developed. In the first stage, conventional FWI is used to achieve rough estimates of the P- and S-wave velocities. In the second stage, we only invert the P-wave velocity applying the separated P-wavefields when strong S-wave energy is involved, or we merely update the S-wave velocity by matching the separated S-wavefields for the weak S-wave case. The PP and PS gradient formulas are used in these two cases, respectively. Therefore, the nonlinearity of inversion and the crosstalk between parameters are greatly reduced. In the third stage, the multistep-length gradient scheme is adopted. The density structure can be improved owing to the use of individual step lengths for different parameters. In the fourth stage, we make minor adjustments to the recovered P- and S-wave velocities and density by implementing conventional FWI again. Synthetic examples have determined that our hierarchical FWI scheme with the aforementioned steps obtains more plausible models than the conventional method. Inversion results of each stage and any three stages reveal that wavefield decomposition and the multistep-length approach are helpful to improve the accuracy of velocities and density, respectively, and all the stages of our hierarchical FWI method are necessary to give a good recovery of P- and S-wave velocities and density.

scholarly journals Post-collisional mantle delamination in the Dinarides implied from staircases of Oligo-Miocene uplifted marine terraces

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Philipp Balling ◽  
Christoph Grützner ◽  
Bruno Tomljenović ◽  
Wim Spakman ◽  
Kamil Ustaszewski
Keyword(s):  
Balkan Peninsula ◽  
Receiver Functions ◽  
P Wave ◽  
S Wave ◽  
Slab Geometry ◽  
Surface Uplift ◽  
River Incision ◽  
Marine Terraces ◽  
Convergence System ◽  
Internal Dinarides

AbstractThe Dinarides fold-thrust belt on the Balkan Peninsula resulted from convergence between the Adriatic and Eurasian plates since Mid-Jurassic times. Under the Dinarides, S-wave receiver functions, P-wave tomographic models, and shear-wave splitting data show anomalously thin lithosphere overlying a short down-flexed slab geometry. This geometry suggests a delamination of Adriatic lithosphere. Here, we link the evolution of this continental convergence system to hitherto unreported sets of extensively uplifted Oligocene–Miocene (28–17 Ma) marine terraces preserved at elevations of up to 600 m along the Dinaric coastal range. River incision on either side of the Mediterranean-Black Sea drainage divide is comparable to the amounts of terrace uplift. The preservation of the uplifted terraces implies that the most External Dinarides did not experience substantial deformation other than surface uplift in the Neogene. These observations and the contemporaneous emplacement of igneous rocks (33–22 Ma) in the internal Dinarides suggest that the Oligo-Miocene orogen-wide uplift was driven by post-break-off delamination of the Adriatic lithospheric mantle, this was followed by isostatic readjustment of the remaining crust. Our study details how lithospheric delamination exerts an important control on crustal deformation and that its crustal signature and geomorphic imprint can be preserved for millions of years.

scholarly journals S-wave experiments for the exploration of a deep geothermal carbonate reservoir in the German Molasse Basin

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Britta Wawerzinek ◽  
Hermann Buness ◽  
Hartwig von Hartmann ◽  
David C. Tanner
Keyword(s):  
Upper Jurassic ◽  
Carbonate Reservoir ◽  
P Wave ◽  
Seismic Survey ◽  
Seismic Exploration ◽  
Molasse Basin ◽  
S Wave ◽  
Induced Earthquakes ◽  
Conversion Point ◽  
Facies Classification

AbstractThere are many successful geothermal projects that exploit the Upper Jurassic aquifer at 2–3 km depth in the German Molasse Basin. However, up to now, only P-wave seismic exploration has been carried out. In an experiment in the Greater Munich area, we recorded S-waves that were generated by the conventional P-wave seismic survey, using 3C receivers. From this, we built a 3D volume of P- to S-converted (PS) waves using the asymptotic conversion point approach. By combining the P-volume and the resulting PS-seismic volume, we were able to derive the spatial distribution of the vp/vs ratio of both the Molasse overburden and the Upper Jurassic reservoir. We found that the vp/vs ratios for the Molasse units range from 2.0 to 2.3 with a median of 2.15, which is much higher than previously assumed. This raises the depth of hypocenters of induced earthquakes in surrounding geothermal wells. The vp/vs ratios found in the Upper Jurassic vary laterally between 1.5 and 2.2. Since no boreholes are available for verification, we test our results against an independently derived facies classification of the conventional 3D seismic volume and found it correlates well. Furthermore, we see that low vp/vs ratios correlate with high vp and vs velocities. We interpret the latter as dolomitized rocks, which are connected with enhanced permeability in the reservoir. We conclude that 3C registration of conventional P-wave surveys is worthwhile.

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