Elastic gaussian beam imaging of walk-away VSP data.

Abstract In vertical seismic profiling (VSP) exploration, it is difficult to produce an accurate image for large-offset reflections only using reflection waves and the image resolution is low in traditional VSP-CDP stacking as is the number of folds of reflection points. To mitigate these problems, we present an inverse Gaussian beam stacking method for imaging both primary reflections and free-surface multiples. We first compute the stacking weighted functions at each trace location by Gaussian beam forward modeling, and then apply an inverse projection for VSP data to produce common shot gathers (CRP). Since inverse Gaussian beam stacking maps the common-shot data along finite-frequency wave-paths instead of single rays as the traditional ray-based stacking method does, it enlarges the reflection-point coverage, increases stacking fold and reduces the requirement for large bin sizes. We incorporate free-surface multiples into the proposed inverse Gaussian beam stacking, which enables us to expand the horizontal imaging aperture and mitigate the low-fold problem of primary reflections in the shallow large-offset regions for VSP surveys. Numerical examples for synthetic and field data demonstrate the feasibility and adaptability of the proposed inverse Gaussian beam stacking method for VSP data.

Download Full-text

A Methodology for 3D Elastic Depth Imaging of Marine 3D Walk-Away VSP Data

10.3997/2214-4609-pdb.131.gen1997_e046 ◽

1997 ◽

Author(s):

S. Østmo ◽

R. Mittet ◽

M. Landrø ◽

K. Hokstad

Keyword(s):

Walk Away ◽

Depth Imaging ◽

Vsp Data

Download Full-text

Some statistical consideration of azimuth and inclination angles determination based on walk - away VSP data in Python

E3S Web of Conferences ◽

10.1051/e3sconf/201913301006 ◽

2019 ◽

Vol 133 ◽

pp. 01006

Author(s):

Mateusz Zaręba ◽

Tomasz Danek ◽

Michal Stefaniuk

Keyword(s):

Measurement Errors ◽

Common Knowledge ◽

Walk Away ◽

Geological Medium ◽

Depth Level ◽

Depth Analysis ◽

Statistical Consideration ◽

Inclination Angles ◽

Vsp Data ◽

The Impact

It is a common knowledge that proper inclinations and azimuth angle determination is a critical step in processing and interpretation of walk-away VSP data. Additionally, an in-depth analysis of the uncertainty of these interpreted values requires the introduction of measurement errors. In this contribution, we present a statistical analysis of obtained polarization angles from three-component, multi-depth level, walk-away VSP using Python 3 programming language. Our analysis is presented in the context of different processing sequences and correlation with local features of the geological medium. We show that the obtained values of polarization angles and their errors can be strongly affected by processing sequence and - when done correctly - can give addition inside into features of analysis medium. Moreover, in some cases, even a presence of saturation can be express by polarization angles variations. Additionally, we examined the impact of well-casing on interpretational values of polarization angles.

Download Full-text

Transforming walk‐away VSP data into reverse VSP data

Geophysics ◽

10.1190/1.1443862 ◽

1995 ◽

Vol 60 (4) ◽

pp. 968-977 ◽

Cited By ~ 13

Author(s):

Rune Mittet ◽

Ketil Hokstad

Keyword(s):

Synthetic Data ◽

Computer Time ◽

Elastic Model ◽

Data Sets ◽

Walk Away ◽

Vertical Seismic Profiling ◽

Experimental Configuration ◽

Vsp Data ◽

Using Data ◽

High Order Finite Difference

Marine walk‐away vertical seismic profiling (VSP) data can be transformed into reverse VSP data using an elastic reciprocity transformation. A reciprocity transform is derived and tested using data generated with a 2-D high‐order, finite‐difference modeling scheme in a complex elastic model. First, 201 shots are generated with a walk‐away VSP experimental configuration. Both the x‐component and the z‐component of the displacement are measured. These data are collected in two common receiver data sets. Then two shots are generated in a reverse VSP configuration. We demonstrate that subtraction of the reverse VSP data from the walk‐away VSP data gives very small residuals. The transformation of walk‐away data into reverse VSP data makes prestack shot‐domain migration feasible for walk‐away data. Synthetic data from a multishot walk‐away experiment can be obtained from one or a few modeling operations with a RVSP experimental configuration. The required computer time is reduced by two orders of magnitude.

Download Full-text