Reconstruction of reflecting structures from vertical seismic profiles with a moving source

Geophysics ◽  
1986 ◽  
Vol 51 (10) ◽  
pp. 1923-1938 ◽  
Author(s):  
K. Köhler ◽  
M. Koenig
Keyword(s):  
Seismic Profile ◽  
Seismic Velocities ◽  
Reflection Point ◽  
Constant Depth ◽  
Seismic Profiles ◽  
Point Mapping ◽  
Resolution Power ◽  
Vertical Seismic Profiles ◽  
Kirchhoff Migration ◽  
Walkaway Vsp

When a vertical seismic profile (VSP) is recorded, the illuminated part of a reflector depends upon the shape and position of the reflector itself as well as on the seismic velocities and the positions of sources and receivers. A preferable arrangement for the investigation of structures of reflectors is to fix the receiver(s) at constant depth(s) in the well and move the source horizontally along a line at the Earth’s surface, usually called a “multioffset VSP” (MSP) or “walkaway VSP.” As a test of the resolution power of this survey geometry, synthetic records were generated from a subsurface model by inverse Kirchhoff migration. Three different methods were applied for the reconstruction. Wavefront construction leads to the correct shape of the reflectors, thus assuring the validity of the modeling method applied. Reflection‐point mapping delivered a near similarity to the model, but without focusing fault edges. Kirchhoff migration resulted in a detailed image of the reflectors with fault edges focused. Application of reflection‐point mapping and Kirchhoff migration to a real survey delivered results consistent with results from a survey at the Earth’s surface.

Traveltime inversion of offset vertical seismic profiles—A feasibility study

Geophysics ◽  
1984 ◽  
Vol 49 (3) ◽  
pp. 250-264 ◽  
Author(s):  
L. R. Lines ◽  
A. Bourgeois ◽  
J. D. Covey
Keyword(s):  
Inverse Method ◽  
Synthetic Data ◽  
Real Data ◽  
Seismic Profile ◽  
Inversion Method ◽  
Earth Model ◽  
Seismic Profiles ◽  
Traveltime Inversion ◽  
Vertical Seismic Profiles ◽  
Inversion Techniques

Traveltimes from an offset vertical seismic profile (VSP) are used to estimate subsurface two‐dimensional dip by applying an iterative least‐squares inverse method. Tests on synthetic data demonstrate that inversion techniques are capable of estimating dips in the vicinity of a wellbore by using the traveltimes of the direct arrivals and the primary reflections. The inversion method involves a “layer stripping” approach in which the dips of the shallow layers are estimated before proceeding to estimate deeper dips. Examples demonstrate that the primary reflections become essential whenever the ratio of source offset to layer depth becomes small. Traveltime inversion also requires careful estimation of layer velocities and proper statics corrections. Aside from these difficulties and the ubiquitous nonuniqueness problem, the VSP traveltime inversion was able to produce a valid earth model for tests on a real data case.

Multichannel Wiener deconvolution of vertical seismic profiles

Geophysics ◽  
1994 ◽  
Vol 59 (10) ◽  
pp. 1500-1511 ◽  
Author(s):  
Jakob B. U. Haldorsen ◽  
Douglas E. Miller ◽  
John J. Walsh
Keyword(s):  
Least Squares ◽  
Amplitude Spectrum ◽  
Seismic Source ◽  
Seismic Profile ◽  
Signal Spectrum ◽  
Seismic Profiles ◽  
Vertical Seismic Profiles ◽  
Vsp Data ◽  
Zero Offset ◽  
Noise Signature

We describe a technique for performing optimal, least‐squares deconvolution of vertical seismic profile (VSP) data. The method is a two‐step process that involves (1) estimating the source signature and (2) applying a least‐squares optimum deconvolution operator that minimizes the noise not coherent with the source signature estimate. The optimum inverse problem, formulated in the frequency domain, gives as a solution an operator that can be interpreted as a simple inverse to the estimated aligned signature multiplied by semblance across the array. An application to a zero‐offset VSP acquired with a dynamite source shows the effectiveness of the operator in attaining the two conflicting goals of adaptively spiking the effective source signature and minimizing the noise. Signature design for seismic surveys could benefit from observing that the optimum deconvolution operator gives a flat signal spectrum if and only if the seismic source has the same amplitude spectrum as the noise.

New insights into the structure of the Sudbury Igneous Complex from downhole seismic studies

2002 ◽  
Vol 39 (6) ◽  
pp. 943-951 ◽  
Author(s):  
David Snyder ◽  
Gervais Perron ◽  
Karen Pflug ◽  
Kevin Stevens
Keyword(s):  
Seismic Data ◽  
Seismic Profile ◽  
Seismic Profiles ◽  
Igneous Complex ◽  
Impact Melt ◽  
Vertical Seismic Profiles ◽  
Sudbury Igneous Complex ◽  
Common Depth Point ◽  
Deformation Models ◽  
The Impact

New vertical seismic profiles from the northwest margin of the Sudbury impact structure provide details of structural geometries within the lower impact melt sheet (usually called the Sudbury Igneous Complex) and the sublayer norite layer. Vertical seismic profile sections and common depth point transformation images display several continuous reflections that correlate with faults and stratigraphic boundaries logged from drill cores. Of four possible mechanisms that explain repeated rock units, late-stage flow or normal faulting that occurred within the last layers to cool and crystallize might best explain the observations, especially the most prominent reflectors observed in the seismic data. These results reaffirm previously proposed two-stage cooling and deformation models for the impact melt sheet.

Synthetic finite‐offset vertical seismic profiles for laterally varying media

Geophysics ◽  
1985 ◽  
Vol 50 (4) ◽  
pp. 627-636 ◽  
Author(s):  
George A. McMechan
Keyword(s):  
Drill Hole ◽  
Seismic Profile ◽  
Rock Properties ◽  
Seismic Profiles ◽  
One Dimensional ◽  
Vertical Seismic Profiles ◽  
Vsp Data ◽  
Lateral Variations ◽  
Lateral Structure

The analysis of vertical seismic profile (VSP) data is generally directed toward determination of rock properties (such as velocity, impedance, attenuation, and anisotropy) as functions of depth (that is, in a one‐dimensional model). If VSPs are extended to include observations from sources at multiple, finite offsets, then lateral variation in structure near the drill hole can be studied. Synthetic offset VSPs are computed by an acoustic finite‐difference algorithm for two‐dimensional models that include the main types of structural traps. These show that diagnostic lateral variations can be detected and interpreted in VSPs. In a VSP, lateral structure variations may produce changes in the type and number of arrivals, in amplitudes, in time and phase shifts, in interference patterns, in curvature of arrival branches, and in the focusing and defocusing of energy. All of these effects are functions of the positions of the source(s) and receiver(s); numerical modeling is a potentially useful tool for interpretation of VSP data from laterally varying structure.

Borehole seismic surveys for fault delineation in the Dutch North Sea

Geophysics ◽  
1989 ◽  
Vol 54 (9) ◽  
pp. 1091-1100 ◽  
Author(s):  
N. J. van der Poel ◽  
B. R. Cassell
Keyword(s):  
North Sea ◽  
Seismic Data ◽  
Hybrid Approach ◽  
Gas Production ◽  
Reflection Point ◽  
Seismic Profiles ◽  
Point Mapping ◽  
Field Development ◽  
Precise Knowledge ◽  
Borehole Seismic

A significant share of gas production in the Dutch sector of the southern North Sea Basin comes from Permian Rotliegend fault blocks. Precise knowledge of the positions of these faults is necessary for efficient exploitation of the reservoir structures and for future field development strategies. Two areas are presented where the lateral resolution of the surface seismic data was not sufficient to determine positions of major fault block boundaries accurately. Walkaway borehole seismic profiles were shot over each of these areas with the objective of illuminating the fault boundaries to obtain an image with a higher resolution. The images were generated using borehole seismic reflection‐point mapping and migration techniques. Large‐aperture migrations tend to produce unacceptable migration smiles, while reflection‐point mapping is a model‐dependent process. A hybrid approach to these processes was necessary to avoid problems associated with the limited angular illumination permitted by the field acquisition geometries. Reliable images of the fault boundaries were obtained using migration apertures of less than ±5° relative to the structural dips in the background model and by matching that model with the surface seismic and borehole seismic data. The stability of the process and, therefore, the accuracy of the lateral positioning were verified by testing the migration process using a range of apertures.

Migration-based filtering: Applications to geophysical imaging data

Geophysics ◽  
2019 ◽  
Vol 84 (4) ◽  
pp. S219-S228 ◽  
Author(s):  
Jianjian Huo ◽  
Binzhong Zhou ◽  
Qing Zhao ◽  
Iain M. Mason ◽  
Ying Rao
Keyword(s):  
Seismic Profile ◽  
Stoneley Wave ◽  
Imaging Data ◽  
Seismic Profiles ◽  
Coherent Signals ◽  
Vertical Seismic Profiles ◽  
Full Waveform ◽  
Ground Roll ◽  
Geophysical Imaging ◽  
Sonic Logging

Migration is used to collapse “diffractions,” i.e., to focus hyperbolic events that appear in the space-time of a seismic profile — into spots of finite area in the image space. These usually represent scattering objects. However, there are situations in which some of the energy can be focused by migration, and muted without significantly damaging the remaining echoes. Demigration or forward modeling then restores the remaining data, and the removed signals can be rebuilt by subtracting these restored data from the original records. This process can be classified as migration-based filtering. It is demonstrated by synthetic and field data that this filter can be used for suppressing unwanted coherent signals or separating/extracting wavefields of interest: (1) the suppression of ground roll in seismic shot gathers, (2) the suppression of axially guided arrivals in borehole radar profiles, (3) suppressing the direct arrivals to enhance Stoneley-wave reflections in full-waveform sonic logging data, and (4) separating up- and downgoing waves in vertical seismic profiles.

Computer processing of vertical seismic profile data

Geophysics ◽  
1983 ◽  
Vol 48 (3) ◽  
pp. 272-287 ◽  
Author(s):  
Myung W. Lee ◽  
Alfred H. Balch
Keyword(s):  
Seismic Profile ◽  
Computer Processing ◽  
Acoustic Properties ◽  
Well Logs ◽  
Seismic Exploration ◽  
Profile Data ◽  
Seismic Profiles ◽  
Vertical Seismic Profiles ◽  
Processing Techniques ◽  
Rock Parameters

Vertical seismic profiles (VSP) are a powerful tool in a variety of seismic exploration situations. Only after extensive computer processing of the raw field data, however, can the full value of this tool be realized. With the help of processing, relations between important rock parameters and acoustic properties can sometimes be established and highly reliable ties from well logs to surface seismic profiles can usually be obtained. The basic theory of the processing techniques is well known. However, the techniques used in processing standard surface seismic profiles usually must be modified to adapt them to the unique conditions associated with VSPs. Processing procedures, and their relevance to the interpretation of VSP and surface seismic profile data, are described.

Wave‐field transformations of vertical seismic profiles

Geophysics ◽  
1987 ◽  
Vol 52 (3) ◽  
pp. 307-321 ◽  
Author(s):  
Liang‐Zie Hu ◽  
George A. McMechan
Keyword(s):  
Fourier Transform ◽  
Wave Field ◽  
Seismic Profile ◽  
Seismic Profiles ◽  
P Waves ◽  
S Waves ◽  
Vertical Seismic Profiles ◽  
Slice Theorem ◽  
Vsp Data ◽  
T Domain

Vertical seismic profile (VSP) data may be partitioned in a variety of ways by application of wave‐field transformations. These transformations provide insights into the nature of the data and aid in the design of processing operations. Transformations are implemented in a reversible sequence that takes the observed VSP data from the depth‐time (z-t) domain through the slowness‐time intercept (p-τ) domain (by a slant stack), to the slowness‐frequency (p-ω) domain (by a 1-D Fourier transform over τ), to the wavenumber‐frequency (k-ω) domain (by resampling using the Fourier central‐slice theorem), and finally back to the z-t domain (by an inverse 2-D Fourier transform). Multidimensional wave‐field transformations, combined with k-ω, p-ω, and p-τ filtering, can be applied to wave‐field resampling, interpolation, and extrapolation; separation of P-waves and S-waves; separation of upgoing and downgoing waves; and wave‐field decomposition for isolation, identification, and analysis of arrivals.

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