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.

Traveltime inversion using transmitted waves of offset VSP data

Geophysics ◽  
1990 ◽  
Vol 55 (8) ◽  
pp. 1089-1097 ◽  
Author(s):  
Myung W. Lee
Keyword(s):  
Seismic Profile ◽  
Inversion Method ◽  
Earth Model ◽  
Computationally Efficient ◽  
Arrival Times ◽  
Traveltime Inversion ◽  
Interval Velocity ◽  
Vsp Data ◽  
First Arrival ◽  
Interval Velocities

Estimation of layer parameters such as interval velocity, reflector depth, and dip can be formulated as a generalized linear inverse problem using observed arrival times. Based on a 2-D earth model, a computationally efficient and accurate formula is derived for traveltime inversion. This inversion method is applied to offset vertical seismic profile (VSP) data for estimating layer parameters using only transmitted first‐arrival times. As opposed to a layer‐stripping method, this method estimates all layer parameters simultaneously, thus reducing the cumulative error resulting from the errors in the upper layers. This investigation indicates (1) at least two source locations are required to estimate layer parameters properly, and (2) accurate arrival times are essential for computing the dip of a layer reliably. Bulk time shifts, such as static shifts, do not affect the parameter estimation significantly if the amount of shift is not too large. The result of real and modeled VSP data inversions indicates that traveltime inversion using transmitted first‐arrival times from at least two source locations is a viable method for estimating interval velocities, reflector depths, and reflector dips.

Detection and measure of the shear‐wave birefringence from vertical seismic data: Theory and applications

Geophysics ◽  
1992 ◽  
Vol 57 (11) ◽  
pp. 1463-1481 ◽  
Author(s):  
Frédéric Lefeuvre ◽  
Laurence Nicoletis ◽  
Valérie Ansel ◽  
Christian Cliet
Keyword(s):  
Shear Wave ◽  
Least Squares Method ◽  
Synthetic Data ◽  
Real Data ◽  
Original Method ◽  
Depth Interval ◽  
Seismic Profiles ◽  
Data Set ◽  
Vertical Seismic Profiles ◽  
The Matrix

An original method is presented that allows us to measure the local shear‐wave birefringence properties over any depth interval. It requires the acquisition of two shear‐wave vertical seismic profiles (VSPs), each with different initial polarizations of the shear wave. The method is based on the estimation of a two by two matrix (called the propagator matrix) that represents a linear operator between two states of polarization. No information is required about layering above the zone of interest (in particular, about the weathering zone). If these two states of polarization correspond to the direct downgoing shear wave at two different depths [Formula: see text] and [Formula: see text], the operator represents the transmission properties between the two depths. Under the previous hypothesis, this operator is independent of the source polarization and can be accurately estimated by a least‐squares method in the frequency domain. Physically, this operator is a multicomponent deconvolution, whose column vectors represent the state of polarizations at a depth [Formula: see text] for two linear and mutually perpendicular polarizations at depth [Formula: see text]. This allows for the measurement of the birefringence properties in all azimuthal directions to determine the directions for which a linearly polarized shear‐wave propagates. In addition, the method can be applied to perform the deconvolution of the upgoing wavefield by the downgoing wavefield to obtain a reflection matrix. Then the matrix can be interpreted in terms of anisotropy below the receiver depths (particularly below the well bottom) and in terms of anisotropy of the reflector itself. The proposed method is validated on synthetic data and is applied to real data from the Paris basin. For this particular data set, the birefringence is located in two layers; the first layer consists of unproductive sands and clays while the second one corresponds to a carbonate oil reservoir from the Dogger formation. The natural directions in both layers are very close to the main directions known for the regional stress field. The presence of fractures in the reservoir layer can explain the strong birefringence ratio (>6 percent).

Vertical seismic profile migration using the Kirchhoff integral

Geophysics ◽  
1988 ◽  
Vol 53 (6) ◽  
pp. 786-799 ◽  
Author(s):  
P. B. Dillon
Keyword(s):  
Wave Equation ◽  
Wave Field ◽  
Near Field ◽  
Synthetic Data ◽  
Real Data ◽  
Seismic Profile ◽  
Processing Strategies ◽  
Receiver Array ◽  
Vsp Data ◽  
Kirchhoff Integral

Wave‐equation migration can form an accurate image of the subsurface from suitable VSP data. The image’s extent and resolution are determined by the receiver array dimensions and the source location(s). Experiments with synthetic and real data show that the region of reliable image extent is defined by the specular “zone of illumination.” Migration is achieved through wave‐field extrapolation, subject to an imaging procedure. Wave‐field extrapolation is based upon the scalar wave equation and, for VSP data, is conveniently handled by the Kirchhoff integral. The migration of VSP data calls for imaging very close to the borehole, as well as imaging in the far field. This dual requirement is met by retaining the near‐field term of the integral. The complete integral solution is readily controlled by various weighting devices and processing strategies, whose worth is demonstrated on real and synthetic data.

Measurements of attenuation from vertical seismic profiles by iterative modeling

Geophysics ◽  
1985 ◽  
Vol 50 (6) ◽  
pp. 931-949 ◽  
Author(s):  
Michel Dietrich ◽  
Michel Bouchon
Keyword(s):  
Velocity Dispersion ◽  
Synthetic Data ◽  
Layered Media ◽  
Spectral Ratio ◽  
Ratio Method ◽  
Seismic Profiles ◽  
Vertical Seismic Profiles ◽  
Anelastic Attenuation ◽  
Vsp Data ◽  
Intrinsic Dissipation

We present a numerical simulation of vertical seismic profiles (VSP) using the discrete horizontal wavenumber representation of seismic wave fields. The theoretical seismograms are computed in the acoustic case for flat layered media, and they include the effects of absorption and velocity dispersion. A study using the synthetic seismograms was conducted to investigate the accuracy and resolution of attenuation measurements from VSP data. It is shown that in finely layered media estimates of the anelastic attenuation obtained by use of the reduced spectral ratio method are usually inaccurate when the attenuation is measured over a small vertical extent. An iterative method is presented which improves the resolution of the measurements of intrinsic dissipation. This method allows determination for synthetic data of the quality factor over depth intervals of about one wavelength of the dominant seismic frequency.

Curved‐ray traveltime inversion of shallow vertical seismic profiles

2002 ◽  
Author(s):  
Geoff Moret ◽  
William P. Clement ◽  
Michael D. Knoll
Keyword(s):  
Seismic Profiles ◽  
Traveltime Inversion ◽  
Vertical Seismic Profiles

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.

Tomographic determination of three‐dimensional seismic velocity structure using well logs, vertical seismic profiles, and surface seismic data

Geophysics ◽  
1987 ◽  
Vol 52 (8) ◽  
pp. 1085-1098 ◽  
Author(s):  
Stephen K. L. Chiu ◽  
Robert R. Stewart
Keyword(s):  
Velocity Structure ◽  
Seismic Velocity ◽  
Random Noise ◽  
Three Dimensional ◽  
Real Data ◽  
Well Logs ◽  
Seismic Profiles ◽  
Vertical Seismic Profiles ◽  
The Earth ◽  
Vsp Data

A tomographic technique (traveltime inversion) has been developed to obtain a two‐ or three‐dimensional velocity structure of the subsurface from well logs, vertical seismic profiles (VSP), and surface seismic measurements. The earth was modeled by continuous curved interfaces (polynomial or sinusoidal series), separating regions of constant velocity or transversely isotropic velocity. Ray tracing for each seismic source‐receiver pair was performed by solving a system of nonlinear equations which satisfy the generalized Snell’s law. Surface‐to‐borehole and surface‐to‐surface rays were included. A damped least‐squares formulation provided the updating of the earth model by minimizing the difference between the traveltimes picked from the real data and calculated traveltimes. Synthetic results indicated the following conclusions. For noise‐free cases, the inversion converged closely from the initial guess to the true model for either surface or VSP data. Adding random noise to the observations and performing the inversion indicated that (1) using surface data alone allows reconstruction of the broad velocity structure but with some inaccuracy; (2) using VSP data alone gives a very accurate but laterally limited velocity structure; and (3) the integration of both data sets produces a more laterally extensive, accurate image of the subsurface. Finally, a field example illustrates the viability of the method to construct a velocity structure from real data.

scholarly journals PEMODELAN INVERSI DATA MAGNETOTELLURIK 1-D MENGGUNAKAN METODA GENETIC ALGORITHM (GA) DENGAN POPULASI MICRO GENETIC ALGORITHM KASUS 3 LAYER DAN 5 LAYER

2019 ◽  
Vol 8 (2) ◽  
pp. 167-180
Author(s):  
Nia Maharani
Keyword(s):  
Genetic Algorithm ◽  
Natural Selection ◽  
Selection Process ◽  
Synthetic Data ◽  
Inversion Method ◽  
Earth Model ◽  
Observation Data ◽  
Linear Inversion ◽  
Synthetic Model ◽  
Micro Genetic Algorithm

This paper discusses non-linear inversion method with Genetic Algorithm (GA) which inspired by natural selection process (survival for the fittest) and genetic using 20 populations (micro genetic algorithm). The method is applied to 1-D magnetotelluric inverted data with model parameter is resistivity as a function of depth. This research only uses synthetic data obtained from synthetic model. The model is homogeneous earth model with 3 and 5 layers. Perturbation of model is performed until minimum misfit between theoritical and observation data achieved. The 3 layers and 5 layers inversion processes are applied to 3 layers and 5 layers earth model respectively, with satisfactory results in other words it can reproduce the synthetic model.

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.

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