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Keywords: horizontal velocity

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Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the SEG International Exposition and Annual Meeting, September 15–20, 2019

Paper Number: SEG-2019-3211288

... king abdullah university efficient wavefield inversion reservoir characterization inversion optimization problem velocity model acoustic vti media upstream oil & gas

**horizontal****velocity**equation Alkhalifah , T. , 2016 , Research note: Insights into the data dependency...
Abstract

ABSTRACT Full-waveform inversion (FWI) is now often used to retrieve high-resolution velocity models in marine datasets. Directly matching the predicted data with the recorded ones at the sensor locations, results in a highly nonlinear optimization problem. Besides its inherent high nonlinearity (manifested in one form in the cycle-skipping problem), considering the anisotropic reality of the true Earth, a multi-parameter inversion imposes additional Null space and the tradeoff issues. To solve these problems, we formulate an optimization problem referred to as an efficient wavefield inversion (EWI) to retrieve multi-parameters. EWI uses background models to reconstruct the wavefield efficiently by introducing an enhanced source function (which includes secondary sources). In this setup, the inversion for the wavefield is linear and efficient. The anisotropic parameters are inverted in a separate direct optimization using the wavefield and the enhanced source function in an efficient matter (no modeling involved). We demonstrate the effectiveness of the proposed method on an Australian marine real data, and compare inverted results with check shot velocity information from a well. Presentation Date: Tuesday, September 17, 2019 Session Start Time: 9:20 AM Presentation Time: 9:20 AM Location: Poster Station 13 Presentation Type: Poster

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 2017 SEG International Exposition and Annual Meeting, September 24–29, 2017

Paper Number: SEG-2017-17740527

... underestimated. Analysis of simple reflection coef- ficient solutions based on linearized approximations helps to explain why the inversion obtains the

**horizontal****velocity**of the shale. Though the linearized results are only applicable for lower values of kerogen volume fraction, the nonlinear in- version based...
Abstract

ABSTRACT Reliable estimation of seismic and geomechanical properties of organic-rich shale provides important constraints to guide production by identifying sweet spots and locations for effective hydraulic fracturing. We investigate the feasibility of amplitude variation with offset (AVO) inversion based on the full Zoeppritz solutions for reflection amplitudes and the ability of the inversion to constrain important properties. By theoretical analysis and inversion tests, we determine behaviors of the AVO inversion solutions developed for isotropic media when the target shale formation instead has seismic anisotropy related to organic content. The anisotropy of the model shale is related to the kerogen volume fraction values using published laboratory data. Both theoretical results and inversion tests show that the inversion accurately determines normal incidence impedance, but that the velocity value corresponds to the horizontal P-wave velocity in the shale so that density is typically underestimated. Analysis of simple reflection coefficient solutions based on linearized approximations helps to explain why the inversion obtains the horizontal velocity of the shale. Though the linearized results are only applicable for lower values of kerogen volume fraction, the nonlinear inversion based on the full Zoeppritz results obtains reliable results even for strong anisotropy. The results also allow the estimation of Young’s modulus and the Poisson ratio. Based on the results and the analysis, we propose a workflow using this approach for shale reservoir characterization to define geophysical and geomechanical properties in both horizontal and vertical directions. Presentation Date: Monday, September 25, 2017 Start Time: 2:15 PM Location: Exhibit Hall C, E-P Station 3 Presentation Type: EPOSTER

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 2017 SEG International Exposition and Annual Meeting, September 24–29, 2017

Paper Number: SEG-2017-17587478

... parameterized perturbation approximation defined by vertical and

**horizontal****velocities**and three cross-term anellipticity parameters results in the best accuracy comparing with the perturbation approximation using other parameterizations. Introduction The traveltime approximations are commonly used in seismic...
Abstract

ABSTRACT We define the new parameterizations for P-wave in acoustic orthorhombic (ORT) media with three cross-term anellipticity parameters and NMO velocities. Using proposed parameterizations, we develop the perturbation series for traveltime function. To stabilize the perturbation series and improve the accuracy, the Shanks transform is applied for all approximations. From the comparison in numerical examples, the new parameterized perturbation approximation defined by vertical and horizontal velocities and three cross-term anellipticity parameters results in the best accuracy comparing with the perturbation approximation using other parameterizations. Presentation Date: Tuesday, September 26, 2017 Start Time: 3:30 PM Location: 360D Presentation Type: ORAL

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 2016 SEG International Exposition and Annual Meeting, October 16–21, 2016

Paper Number: SEG-2016-13867221

... variables are the

**horizontal****velocity**, = and the perturbation. Application to the anisotropic version of Marmousi model with a single frequency of 2.5 Hz shows that this method can converge to the accurate result starting from a linearly increasing isotropic initial velocity. Application to a real...
Abstract

ABSTRACT Reflected waveform inversion (RWI) provides a method to reduce the nonlinearity of the standard full waveform inversion (FWI) by inverting for the background model using a single scattered wavefield from an inverted perturbation. However, current RWI methods are mostly based on isotropic media assumption. We extend the idea of the combining inversion for the background model and perturbations to address transversely isotropic with a vertical axis of symmetry (VTI) media taking into consideration of the optimal parameter sensitivity information. As a result, we apply Born modeling corresponding to perturbations in only for the variable to derive the relative reflected waveform inversion formulation. To reduce the number of parameters, we assume the background part of and work with a single variable to describe the anisotropic part of the wave propagation. Thus, the optimization variables are the horizontal velocity , = and the perturbation. Application to the anisotropic version of Marmousi model with a single frequency of 2.5 Hz shows that this method can converge to the accurate result starting from a linearly increasing isotropic initial velocity. Application to a real dataset demonstrates the versatility of the approach. Presentation Date: Tuesday, October 18, 2016 Start Time: 1:25:00 PM Location: 146 Presentation Type: ORAL

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 2016 SEG International Exposition and Annual Meeting, October 16–21, 2016

Paper Number: SEG-2016-13863627

... Date: Tuesday, October 18, 2016 Start Time: 1:50:00 PM Location: 166 Presentation Type: ORAL

**horizontal****velocity**non-uniqueness problem optimization seg seg international exposition log measurement correction anisotropy log analysis well logging annual meeting vti parameter...
Abstract

ABSTRACT This paper proposes a method for the correction of sonic logs for anisotropy (deviation) effects using constrained optimization for formations with vertically transverse isotropic (VTI) symmetry. The accuracy of this technique was investigated using sonic data from several wells as well as ultrasonic velocity measurements. Only the results obtained from ultrasonic measurements are presented because of data confidentiality. A point by point correction is proposed, which does not necessarily require borehole angle coverage within the anisotropic formation. It also does not require compaction effects removal because each data point is processed independently from the data points above and below it. In the absence of angle coverage in the anisotropic formation, both point by point and interval-based approaches become an under-determined problem because, in this case, there will be more unknowns than equations. To address the non-uniqueness of the point by point approach, this paper shows how velocity trends can be used to constrain the solutions. Simulation results using lab data show that a rough estimate of Thomsen parameters (e.g., using average values for each shale from published values) can be used to reconstruct vertical, horizontal, and 45° velocities with average correlation coefficients of more than 95%. The other type of S-wave (V), which is assumed not to be measured using a monopole source, can be also recovered with correlation coefficient more than 95%. Presentation Date: Tuesday, October 18, 2016 Start Time: 1:50:00 PM Location: 166 Presentation Type: ORAL

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 2016 SEG International Exposition and Annual Meeting, October 16–21, 2016

Paper Number: SEG-2016-13953250

...) to the long and short wavelength components of the anisotropic parameters. Considering the low sensitivity of FWI to the anellipticity parameter when parametrizing the acoustic transversely isotropic model with the

**horizontal****velocity**, and , we develop a combined FWI and reflection waveform inversion (RWI...
Abstract

ABSTRACT Addressing anisotropy in full wavenumber inversion (FWI) is crucial to obtaining credible models, and it is extremely challenging considering the multi parameter nature of the inversion. A successful FWI in anisotropic media takes into account the sensitivity of the data (or the wave) to the long and short wavelength components of the anisotropic parameters. Considering the low sensitivity of FWI to the anellipticity parameter when parametrizing the acoustic transversely isotropic model with the horizontal velocity, and , we develop a combined FWI and reflection waveform inversion (RWI) to invert for the anisotropic parameters that influence surface seismic data. This practical waveform inversion (PWI) separates the parameters to their resolvable scales, with information accessed from the data fitting (FWI) and the image focusing (RWI) objectives. With this parametrization, the RWI role is to obtain a smooth model, as well as velocity, while FWI focusses on the scattering potential of the horizontal velocity. The parameter is used to produce the Born scattered wave-field for the RWI part and eventually fit the amplitude for the imperfect physics in the FWI part. Presentation Date: Wednesday, October 19, 2016 Start Time: 2:20:00 PM Location: 162/164 Presentation Type: ORAL

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 2016 SEG International Exposition and Annual Meeting, October 16–21, 2016

Paper Number: SEG-2016-13611846

... and

**horizontal****velocities**. We start with transversely isotropic medium with a vertical symmetry axis (VTI) and extend this approach to orthorhombic (ORT) medium. In order to stabilize the perturbation series, the Shanks transform is applied for the cases. The new moveout approximations result in better accuracy...
Abstract

ABSTRACT We propose a new moveout approximation based on an alternative background model. The standard approach is based on elliptical background model with two velocities, vertical and normal moveout ones. We suggest to use another elliptical background model defined with vertical and horizontal velocities. We start with transversely isotropic medium with a vertical symmetry axis (VTI) and extend this approach to orthorhombic (ORT) medium. In order to stabilize the perturbation series, the Shanks transform is applied for the cases. The new moveout approximations result in better accuracy comparing with the standard perturbation based methods. Presentation Date: Wednesday, October 19, 2016 Start Time: 2:20:00 PM Location: Lobby D/C Presentation Type: POSTER

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 2015 SEG Annual Meeting, October 18–23, 2015

Paper Number: SEG-2015-5856899

... geophysics upstream oil & gas media annual international meeting gradient

**horizontal****velocity**inversion hess vti model reflectivity jmi berkhout cost function Robust anisotropy estimation using joint migration inversion Abdulrahman Alshuhail and D.J. Verschuur, Delft University...
Abstract

Summary Several methods utilize the full waveform to estimate anisotropy from surface seismic data. Their apparent weaknesses is usually in the dependency on initial model and in the non-uniqueness of the inverted parameters. In this paper we investigate the feasibility and robustness of incorporating anisotropic inversion in JMI, in that we estimate reflectivity, velocity, and anisotropy on the fly. We do this by analyzing the cost function associated with anisotropic inversion in JMI. By coupling anisotropy and velocity inversion with reflectivity inversion it is possible to reduce the dependency on the initial model. Hence, making the method less susceptible to local minima. On the other hand, the non-uniqueness problem is mitigated by acquiring the far offsets, we show the effect of acquiring the far offsets on the cost function as a comparison. We present the new gradient for anisotropic inversion and test its effectiveness on the HESS VTI model. Introduction Obtaining an accurate image of the subsurface is imperative in seismic exploration. However, in order to obtain an accurate image an accurate velocity model is needed. Nonetheless, obtaining an accurate velocity model is not straight forward. We have seen a shift in the industry to couple velocity estimation with imaging (Sava and Biondi, 2004). We have also seen a shift in the industry to utilize the full waveform (Virieux and Operto, 2009). JMI proposed by Berkhout (2012, 2014c) and implemented by Staal and Verschuur (2012, 2013) combines both. It couples estimation of these two parameters (reflectivity and velocity) while minimizes the error in a full waveform way. The method is completely data driven in that it minimizes the error between the observed data and the calculated data. JMI utilizes both the internal and surface-related multiples in defining the reflectivity and velocity models. Since multiples generally spend more time bouncing in the subsurface they are generally more sensitive to the velocity model. This not only translates to a better image and a better velocity model but it also means that the crosstalk issue is automatically taken into account. Accounting and honoring anisotropy (when it is present) produces superior results in JMI as opposed to ignoring them (Alshuhail and Verschuur, 2014). This is especially the case for wide azimuth and wide aperture surveys, since more waves travel in a horizontal sense. However, in order to account for anisotropy one must know the anisotropy model. Therefore, estimating anisotropy on the fly along with reflectivity and velocity will present a more complete framework for the JMI method in anisotropic media. The modeling engine behind JMI is Full Wavefield Modeling (FWMod). It explains seismic reflection response in terms of amplitude and phase changes, which translate to reflectivity and velocity respectively (Berkhout, 2014a). Alshuhail and Verschuur (2014) updated the FWMod method to account for Vertical Transpose Isotropy (VTI) media. They build upon this work and incorporated anisotropy in the JMI framework. In this paper we investigate the robustness of anisotropic inversion in JMI.

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 2012 SEG Annual Meeting, November 4–9, 2012

Paper Number: SEG-2012-0730

... by the squares of vertical and

**horizontal****velocity**results in vertical velocity and e updates with opposite signs. On the other hand, a model space parametrized by the logarithm of the vertical velocity squared and epsilon has more reasonable updates. However, ambiguity does exist in the inversion results...
Abstract

SUMMARY In this paper I introduce two different model-space parametrizations for early-arrival waveform inversion of velocity and anisotropic parameter. More specifically, I jointly invert for vertical velocity and e parameter, while keeping the d parameter fixed. A model space parametrized by the squares of vertical and horizontal velocity results in vertical velocity and e updates with opposite signs. On the other hand, a model space parametrized by the logarithm of the vertical velocity squared and epsilon has more reasonable updates. However, ambiguity does exist in the inversion results between vertical velocity and e. I demonstrate these using a synthetic example.

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 2011 SEG Annual Meeting, September 18–23, 2011

Paper Number: SEG-2011-2799

... of the Hessian from Bayesian estimation theory and synthetic examples. Our analysis shows that, in the context of macromodel building, namely background estimation, acoustic VTI FWI mainly depends on the normal moveout (NMO) velocity and the

**horizontal****velocity**(or equivalently a combination of these two...
Abstract

ABSTRACT Full waveform inversion (FWI) estimates an optimal set of model parameters by minimizing the error misfit between the modeled and observed data. Here, we study the parametrization for FWI in vertical transversely isotropic (VTI) media by means of eigenvalue/eigenvector analysis of the Hessian from Bayesian estimation theory and synthetic examples. Our analysis shows that, in the context of macromodel building, namely background estimation, acoustic VTI FWI mainly depends on the normal moveout (NMO) velocity and the horizontal velocity (or equivalently a combination of these two velocities). It also points out a possible ambiguity when one inverts for two parameters. This ambiguity is further illustrated with a real data FWI example. The trade-off between velocity heterogeneities and anisotropy also complicates the recovery of the anisotropic parameter ?.

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 2011 SEG Annual Meeting, September 18–23, 2011

Paper Number: SEG-2011-2543

... ABSTRACT Anisotropy can have a significant footprint in seismic imaging from surface wide-aperture data, because of the difference between vertical and

**horizontal****velocities**in vertical transversely isotropic (VTI) media. A key issue in anisotropic full waveform inversion (FWI) is to define...
Abstract

ABSTRACT Anisotropy can have a significant footprint in seismic imaging from surface wide-aperture data, because of the difference between vertical and horizontal velocities in vertical transversely isotropic (VTI) media. A key issue in anisotropic full waveform inversion (FWI) is to define a suitable parametrization of the subsurface model, and the number of parameter classes that can be reliably reconstructed for the chosen parametrization. We address this issue with an application of frequency-domain acoustic isotropic/anisotropic FWI to real surface wide-aperture data recorded by an ocean bottom cable in the Valhall field. Isotropic FWI results show that the horizontal velocity is mainly reconstructed in the upper structure, dominantly constrained by diving waves and supercritical reflections. This can lead to depth stretching and/or overestimated velocity perturbations in the deep velocity structure, mainly controlled by short-aperture reflections. Monoparameter anisotropic FWI shows a reliable reconstruction of either the vertical, the horizontal or the NMO velocity, when the model is parametrized by one wave speed and the Thomsen''s parameters d and e. For such mono-parameter FWI, the smooth d and e background models are kept constant during FWI iterations. Alternatively, the vertical and the horizontal velocities can be jointly reconstructed by multiparameter FWI, when the subsurface model is parametrized by the two wave speeds and d, this latter is kept fixed during FWI iterations.

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 2007 SEG Annual Meeting, September 23–28, 2007

Paper Number: SEG-2007-0134

... anisotropy. Parameterizing the medium ellipticity by the ratio between the squares of the vertical and

**horizontal****velocities**, they showed that time remigration in elliptically anisotropic media is described by the isotropic image wave equation using the**horizontal****velocity**. This agrees with the fact...
Abstract

SUMMARY By reparameterization of the kinematic expressions for remigration in elliptically anisotropic media using a new ellipticity parameter, we derive a new image-wave equation in elliptically anisotropic media, which describes the reflector position as a function of the medium ellipticity. This image-wave equation, which is a kind of medium-dependent one-way wave equation, can be used for automatically stretching a migrated image in depth until wells are tied or other geologic criteria are met. In this way, it is possible to find an estimate of the vertical velocity, which cannot be detected from time processing only. A simple numerical example confirms the validity of the theory. INTRODUCTION In a set of migrated sections obtained using only slightly different velocity model parameters, the reflector images are dislocated only slightly from one to the next. Thus, looking at such a set in fast sequence creates the impression of looking at snapshots of a propagating wavefront. Under the assumption of a constant migration velocity, this “propagation” of reflector images can be described by partial differential equations (Fomel, 1994) that have been termed “image-wave equations” by Hubral et al. (1996). Since the pioneering work of Fomel (1994), many different image-wave equations for different situations have been proposed and their applications have been studied. Recently, Schleicher and Aleixo (2007) extended the theory of imagewave remigration to media with elliptical anisotropy. Parameterizing the medium ellipticity by the ratio between the squares of the vertical and horizontal velocities, they showed that time remigration in elliptically anisotropic media is described by the isotropic image wave equation using the horizontal velocity. This agrees with the fact that the position of a timemigrated reflector image depends only on the variation of the horizontal velocity (Alkhalifah and Tsvankin, 1995). Therefore, assuming that an estimate of the horizontal rather than the vertical velocity is known, we reparameterize the elliptical-anisotropy equations using the ratio between horizontal and vertical velocity as ellipticity parameter. We derive a new image wave equation, which can be used for depth stretching a migrated image until geologic criteria are met. VERTICAL IMAGEWAVES Seismic remigration tries to establish a relationship between two media of wave propagation such that identical seismic surveys on their respective surfaces would yield the same seismic data. One of these media is the wrong velocity model used for the original migration. The other medium represents the updated model within which a new image of the subsurface needs to be constructed. Therefore, the kinematic relationship between these two media is established by equaling the traveltimes of a seismic wave in both of them. Schleicher and Aleixo (2007) parameterized the traveltime of a zero-offset event with source and receiver at point (x ,h,0) on the surface and reflection point at ( x , y , z ) in depth in an elliptically anisotropic medium using j = v 2 u 2as the parameter describing the medium ellipticity, where, u and v are the horizontal and vertical velocities, respectively. This parametrization would be useful if the vertical velocity v was known and the horizontal velocity u was unknown.

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 2006 SEG Annual Meeting, October 1–6, 2006

Paper Number: SEG-2006-3413

... sensitivity analysis stereotomography diffractor approximation media anelliptic media inversion

**horizontal****velocity**ray coverage vertical velocity relative error initial condition geophysics upstream oil & gas anisotropic media Sensitivity Analysis for Stereotomography in Elliptic...
Abstract

ABSTRACT Stereotomography is extended to general anisotropic models and implemented for elliptical and anelliptical anisotropy. Elliptical and anelliptical models depend on three parameters only, which makes them less sensitive to ambiguity due to limited coverage of surface seismic experiments than transversely isotropic or orthorhombic models. The corresponding approximations of the slowness surface restrict the validity of the present approach to qP events and mild anisotropy. Numerical experiments show the potential and the limitations of stereotomography for estimating macrovelocity models in the presence of anisotropy as well as the importance of transmission events from multiple-offset VSP experiments for the success of the approach.

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 2004 SEG Annual Meeting, October 10–15, 2004

Paper Number: SEG-2004-0119

... in weak anisotropy media shows that each traveltime approximation has its own requirements for spread length and subsurface anisotropic parameters. The accuracy of the estimated Thomsen's anisotropic parameter d (or e) depends not only on the accuracy of the picked NMO velocity (or

**horizontal****velocity**...
Abstract

ABSTRACT Anisotropy parameters in a VTI medium can be obtained by anisotropy velocity analysis performed on short-spread or long-spread reflection-seismic data, in combination with check-shot or well-log data. Analysis of three traveltime approximations to the actual reflection traveltime in weak anisotropy media shows that each traveltime approximation has its own requirements for spread length and subsurface anisotropic parameters. The accuracy of the estimated Thomsen's anisotropic parameter d (or e) depends not only on the accuracy of the picked NMO velocity (or horizontal velocity) but also on the absolute value of) (e - d). The smaller the absolute value of (e - d), the higher the accuracy of estimated anisotropy parameter d or e. The results of the three traveltime inversions by semblance analysis for synthetic seismic examples demonstrate that nonhyperbolic estimation is better than the modified three-term Taylor series method, and the modified three-term Taylor series method better than hyperbolic estimation. None of these three approaches is suitable for estimating anisotropy parameters when the absolute value of (e - d) is large (i.e. |e - d| > 0.2 in this case).

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 2004 SEG Annual Meeting, October 10–15, 2004

Paper Number: SEG-2004-0159

... the vertical velocity to be higher than the

**horizontal****velocity**that is uncommon in the conventional sand-shale formations. Since HR is characterized by high velocity hydrate veins, emulating vertical layering, an HTI model (TI with a horizontal axis of symmetry) seems more appropriate. Our anisotropy analysis...
Abstract

ABSTRACT We have observed P-wave seismic anisotropy at the south summit of Hydrate Ridge (HR), Cascadia convergent margin, offshore Oregon, on walkaway vertical seismic profiles and ocean bottom seismometer data. Models based on the assumption of vertical transverse isotropy (VTI), require the vertical velocity to be higher than the horizontal velocity that is uncommon in the conventional sand-shale formations. Since HR is characterized by high velocity hydrate veins, emulating vertical layering, an HTI model (TI with a horizontal axis of symmetry) seems more appropriate. Our anisotropy analysis consists of two-steps, 1) building of 2D anisotropic model comprising homogeneous layers based on the traveltime-error-contour analysis assuming VTI and HTI medium, and 2) derivation of continuously varying heterogeneous model using a rigorous traveltime inversion with very-fast simulated annealing. Based on our result we established relationships between P-wave anisotropic parameters and distribution of gas hydrate and free gas at HR. Observed P-wave anisotropy are, 1) 11% (N-S) to 15% (E-W) in the layer A (from sea floor to 70 meter below sea floor) containing heterogeneous hydrate veins, 2) 7% (N-S) to 10% (E-W) in the layer B (from layer A to bottom simulating reflector) containing relatively homogeneous hydrate and 3) 3% in the layer C (gas-bearing sediments below layer B). Anisotropy values are proportional to the hydrate concentration at the HR. Distribution and concentration of gas-hydrates can be further used for studying possibilities of gas-hydrate as a geohazard, an economic energy source, and a cause for world margin stability and climate change.

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 2003 SEG Annual Meeting, October 26–31, 2003

Paper Number: SEG-2003-0753

... isotropic with a vertical symmetry axis (VTI) media. Near offsets are used to estimate the vertical travel time and normal moveout (NMO) velocity, while the non-hyperbolic moveout of all offsets are fitted to estimate the

**horizontal****velocity**. _ and d parameters are estimated from these velocities...
Abstract

Summary A 12-level 3D vertical seismic profile (VSP) is acquired as part of Weyburn Project with of Reservoir Characterization Project (RCP) at Colorado School of Mines. Travel times from direct arrivals of compressional sources are used to invert for Thomsen’s parameters for a transversely isotropic with a vertical symmetry axis (VTI) media. Near offsets are used to estimate the vertical travel time and normal moveout (NMO) velocity, while the non-hyperbolic moveout of all offsets are fitted to estimate the horizontal velocity. _ and d parameters are estimated from these velocities. A sensitivity and error analysis on the parameters that control the non-hyperbolic moveout equation is performed. Introduction RCP is characterizing a carbonate reservoir that is undergoing CO2 and water injection since 2000.

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 2002 SEG Annual Meeting, October 6–11, 2002

Paper Number: SEG-2002-0129

... as a vertically transversely isotropic (VTI) medium. For such a medium, waves travel vertically and horizontally with different velocities, e.g., Vo (vertical velocity) and Vh (

**horizontal****velocity**). It is well known that the velocities from normal moveout (NMO) analysis are usually higher than those from wells...
Abstract

Summary In many basins around the world, sedimentary rocks can be represented as a vertically transversely isotropic (VTI) medium. For such a medium, waves travel vertically and horizontally with different velocities, e.g., Vo (vertical velocity) and Vh (horizontal velocity). It is well known that the velocities from normal moveout (NMO) analysis are usually higher than those from wells. The difference is due to the fact that NMO analysis measures the wavefront curvature at a near-vertical angle, which is distorted by anisotropy parameterized by ellipticity parameter ? and anellipticity parameter ?, whereas the measurement from a well gives the vertical velocity of a rock matrix.

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 2002 SEG Annual Meeting, October 6–11, 2002

Paper Number: SEG-2002-1979

.... lawrence livermore geophysics original marmousi model upstream oil & gas hydrocarbon seg int algorithm reservoir characterization exploration geophysics dataset modeling avo analysis marmousi model

**horizontal****velocity**p-wave velocity calibration salt lake city exposition national...
Abstract

Summary We have created an elastic version of the IFP Marmousi model for use in AVO analysis in the presence of complex structure. The model is larger, includes larger offsets, lies in deeper water, includes surface streamer, multicomponent OBC and VSP acquisition, and contains more hydrocarbons than its predecessor. In addition to AVO analysis, we believe these data will be suitable for calibrating emerging technologies including converted wave tomography and vector seismic processing. Introduction The application of AVO is taken for granted in relatively simple structural areas, and it has been shown to be very useful. some doubt as to whether it is applicable due to the various imaging problems and amplitude variation caused by effects such as focusing and defocusing. This study details the creation of a new synthetic model and dataset that will enable this to be investigated.

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 2000 SEG Annual Meeting, August 6–11, 2000

Paper Number: SEG-2000-0586

... can be affected by as much as 5 percent from

**horizontal****velocities**. Dipole sonic logs indicate that at greater angles, encountered both by surface and crosswell reflection profiling, velocities may be 20-30 percent less than bedding-plane velocities. anisotropic tomography reservoir...
Abstract

Summary 3D Crosswell tomography has provided incontrovertible evidence of anisotropy in the Santa Rosa field in eastern Venezuela that correlates extremely well with massive shale zones in the Colorado member of the Oficina formation. These shale zones show characteristics of "weak anisotropy" in a transversely isotropic formation with a non-vertical axis of symmetry. Limited angle tomograms derived from raypaths traveling at small angles with respect to bedding (0-20 degrees) show variations in velocities that correlate with increasing angle. At 20 degrees from the bedding velocities can be affected by as much as 5 percent from horizontal velocities. Dipole sonic logs indicate that at greater angles, encountered both by surface and crosswell reflection profiling, velocities may be 20-30 percent less than bedding-plane velocities.

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 2000 SEG Annual Meeting, August 6–11, 2000

Paper Number: SEG-2000-2253

... SUMMARY A linearized eikonal equation is developed for transversely isotropic (TI) media with vertical symmetry axis (VTI). It is linear with respect to perturbations in the

**horizontal****velocity**or the anisotropy parameter h. An iterative linearization of the eikonal equation is used...
Abstract

SUMMARY A linearized eikonal equation is developed for transversely isotropic (TI) media with vertical symmetry axis (VTI). It is linear with respect to perturbations in the horizontal velocity or the anisotropy parameter h. An iterative linearization of the eikonal equation is used as the bases for an algorithm of finite-difference traveltime computations. A practical implementation of this iterative technique suggests starting from a background model of an elliptically anisotropic, inhomogeneous, nature. Especially since, for such media, traveltimes are calculated efficiently using eikonal solvers valid for the isotropic case. This constrains the perturbation to changes in the anisotropy parameter h (the parameter most responsible for imaging improvements in anisotropic media). The iterative implementation includes repetitive calculation of h from