Date

Group

Speakers

Summary

9-7

A-Team

Lorenzo & Praj

Lorenzo

Seismic Anisotropy; Project Review

Abstract:

In this presentation I'll briefly review the projects I worked on up to now. All these projects involved seismic anisotropy as main actor. I'll show different efficient formulations for qP ray tracing in 3D TI media. Then I show how I've used efficiently these forward model codes for both kirchhoff depth imaging and tomographic MVA. Third and last part is devoted to time processing algorithm: I conclude with an original VTI velocity estimation workflow by using local data slopes.

Praj

3D Shear Wave VSP Depth Imaging of Fractured Sandstones in Rulison Field, Colorado

Abstract:
Reservoir rocks in the gas producing interval of Rulison Field, Colorado comprises of tight fractured sandstones that evade detection by P-waves. These sandstones, however, have better shear impedance contrast with the encasing shale. In the current study I use an uncommon, yet very effective procedure that uses non-converted shear waves recorded in a borehole in a 3D VSP survey to image the reservoir interval and beneath. The 3D depth imaging results tie with the well logs and with the existing surface seismic data. The recovered images not only provide a significant uplift in terms of sandstone detection and structure delineation but a quick-look interpretation of images also indicates anisotropy resulting from fractures.

9-14

I-Team

Yong and Francesco

Yong

Image-guided full waveform inversion

Abstract:

Computational cost and nonlinearity are major concerns in full waveform inversion (FWI). We incorporate image-guide interpolation introduced by Hale into FWI, to improve the FWI result and to save computation time.

Francesco

Simultaneous shot migration by means of Pseudo-random sequence convolution encoding

Abstract:

In this presentation I show a preliminary study for translating in the context of seismic imaging a technique successfully applied in telecommunication: Code Division Multiple Access. In wireless communication the problem is sharing the only available channel with a number of interfering users, in the framework of seismic imaging of simultaneous shots it translates in the back-propagation and imaging of different experiments.
I show how I adapted CDMA technique to seismic imaging, the main idea behind this approach and intrinsic issues that need to be addressed.

http://sites.google.com/site/cwpiteam/

9-21

C-Team

Benjamin Kadlec
CU Computer Science and
TerraSpark Geosciences

I combine image structure analysis and implicit surface modeling with an interactive "visulation" environment (IVE) specifically designed to segment geologic features. The IVE allows geoscientists to observe the evolution of surfaces and steer them toward features of interest using their domain knowledge. This work has been implemented on the GPU for increased performance and interaction. The resulting system is a surface-driven solution for the interpretation of 3-D seismic data, in particular for the segmentation and modeling of faults, channels, and other geobodies.

9-28

S-Team

Jae and Rosie

Jae

Inverse scattering series and CSEM exploration

Abstract:

The inverse scattering series (ISS) method is an ideal method for the interpretation of geophysical data because it does not require a priori knowledge about the earth. The ISS method has been studied for seismic exploration and successfully applied for velocity estimation and multiple removal. Using earth models with simple geometry, we extend the application of the ISS method into the diffusion equation and study its applicability to controlled-source electromagnetic (CSEM) exploration. Compared to seismic exploration, CSEM exploration is characterized by fast spatial decay of signal and strong perturbation. Simple model tests reveal that the convergence speed of the inverse series for the diffusion equation is expected to be faster than that for the wave equation. The model tests also show that the convergence of the inverse series is affected by the choice of reference medium properties.

Rosie

Monitoring and modeling subsurface with quasi-static deformation

Abstract:

We're exploring a technology that is based on using low-frequency strain data to monitor changes in fluid saturation conditions in porous media. Today I'll review that data processing part of the project and introduce the methodology of modeling such a quasi-static deformation with natural forces.

10-5

Norm

True amplitude Gaussian beam migration

10-12

C-Team

Derek, Luming and Chris

Derek

Nonlinearity of Flattening

Abstract:

Seismic image flattening is commonly used in the interpretation work flow to map stratigraphic features. The recent advances in full volume seismic image flattening allow one the ability to flatten seismic images without picking horizons. I will review many of these concepts and present a new method for full volume flattening.

Luming

Towards Determination of Displacement Field from Seismic Image

Abstract:

This is about how to find displacement between vertical traces in a seismic image.

Chris

Tensor Field Visualization using Ellipsoids

Abstract:

Tensor fields are used as parameters in various image processing techniques, including structure-oriented smoothing and image-guided interpolation. However, visualizing these parameters has always been a challenge. In this presentation, we explore one method of visualizing tensor fields in the form of ellipsoids.

10-19

Fall break

10-26

SEG Meeting

11-2

I-Team

Andre Bulcao (Petrobras)

http://sites.google.com/site/cwpiteam/

11-9

SEG Review

11-16

A-Team

Mamoru and Yongxia

Mamoru

Correction for the influence of velocity lenses on
nonhyperbolic moveout inversion for VTI media.

Abstract: Nonhyperbolic moveout analysis plays an increasingly important role in velocity model building because acquisition of long-offset data has become more common. However, lateral heterogeneity, typically
associated with small-thickness lenses such as channels and carbonate reefs, can cause significant distortions in the moveout parameters even when the structure is relatively simple. Identifying and correcting these distortions should help build more reliable anisotropic velocity models.
To correct the parameters Vnmo and eta for lateral heterogeneity, we propose an algorithm to remove the lens-induced traveltime distortion from prestack data. Synthetic tests demonstrate that this algorithm successfully eliminates the lens-induced distortions in the stacked section and reduces the errors in the effective and interval parameters Vnmo and eta. The corrected traces and reconstructed “background” values of Vnmo and eta are suitable for performing anisotropic time imaging and for producing a high-quality stack.

Yongxia

Gaussian beam modeling for SV-waves in TI media

Abstract: In certain anisotropic media, SV waves have cuspoidal wavefront. The ray tracing method can not provide a good approximation for the cusps because the ray amplitude at caustic points goes to infinite. Here, the Gaussian beam method is applied to handle the caustics. We talk about the factors for the Gaussian beam summation. The Gaussian beam summation provides a good approximation for the wavefield if we use proper parameters including the beam width, the beam interval and the range of the beam for summation.

11-23

A-Team

Anatoly Levshin

Epicentroidal location based on empirical Green's
functions from ambient seismic noise

Abstract:

A new method for locating the epicenter of regional
seismic events is developed whose strengths and limitations complement existing location methods. This new technique is based on applying Empirical Green's Functions (EGFs) for Rayleigh waves between 7 and 15 sec period that are determined by cross-correlation of ambient noise time-series recorded at pairs of seismic receivers. The important advantage of this method, in comparison with standard procedures based on use of body wave travel times, is that it does not employ an earth model.
The method is tested by locating well known ``Ground Truth" crustal events in the western US as well as locating seismic stations using the principal of reciprocity. In these applications, location errors average less than 1 km.

11-30

S-Team

Filippo

Connection of scattering principles: theory and questions

Clement
General representation theorem for perturbed media & Application to Green's function retrieval for scattering problems

Abstract: Green's function reconstruction relies on representation theorems. For acoustic waves, it has been shown theoretically and observationally that the representation theorem leads to the retrieval of the Green's function by cross-correlating fluctuations recorded at two locations. We extend the theory to any system that satisfies a partial differential equation and analyze Green's function reconstruction for perturbed media. We establish an alternative representation theorem for perturbations. The relation is then applied to the general treatment of scattering problems. We illustrate the concept with a numerical example in the case of an open strongly scattering medium. This reasoning can be applied to any perturbation problem such as electromagnetic waves in conductive media, attenuated elastic waves, or seismic waves in heterogenous media.

12-7

I-Team

Jia and Francesco

http://sites.google.com/site/cwpiteam/

Francesco

Measurement of similarity between migrated images

Abstract: Migration velocity analysis is based on the semblance principle: different experiments "see" the same earth. In other words, the images we obtain from different shots must be consistent with each other, if the velocity model we use for migration is correct. This consistency is usually evaluated once that all the experiments have been imaged; this is expensive and becomes even more costly if the imaging procedure we use is based on a time-domain finite difference scheme.
In this presentation I introduce a new measure for evaluating the consistency of migrated images, directly, for neighboring shots. This measure gives us a new lever for estimating velocity errors and for performing migration velocity analysis in a different and potentially faster way.