Converted Waves

Since the onset of Phase 5 (2000-03),
significant progress has been made in bridging the gap for converted-wave processing and imaging. A common theoretical framework is developed to describe the converted-wave behaviour in anisotropic media in terms of converted wavefield attributes. This paved the way for the use of standard procedures such as semblance analysis and Kirchhoff summation to implement converted-wave anisotropic processing with high accuracy but low cost.

DNO+Stack+migration Anisotropic PSTM

In Phase 6 (2003-06), the previous research developments into 3D- 4C data were extended to both anisotropic imaging and parameter estimation, An user-friendly software, referred to as CXtools was developed. Using this tool, a number of 2D and 3D-4C dataset from the North Sea was reprocessed, and in each case, a substantially improved subsurface image was obtained that has made significant impact on the development of the relevant oilfield.

During Phase 7(2006-09), the emphasis is to extend CXtools to account for the diodic converted-wave effects and further development of our depth-imaging tools for building a common anisotropic earth model, and our aim is to fill the wide acknowledged gap in converted-wave processing with CXtools.

Diodic effect of PS wave Joint PP and Ps velocity analysis

Recently (Phase 8), new GUI tool for joint PP, PS waves velocity analysis and diodic processing has been developed. In converted wave interpretation and inversion, the event registration by using the attribute of reflectivity to convert PP wave into a pseudo PS waves, Joint PP, PS-wave impedance inversion in orthorhombic media and compensation for the azimuthal anisotropy of PS-converted waves in HTI media are also studied.

PP and PS events registration

Joint PP and PS waves inversion for impedance in the ray parameter domain

PS waves in fractured HTI media

Areas of interest and deliverables:

o diodic decomposition for 3D 4C data;

o the corresponding depth imaging work flows using PP-independent PS imaging approach;

o decoupled migration and associated work flows for anisotropic inversion;

o conversion point signature from 3D 4C data;

o anisotropic estimation in TTI media;

o case studies of 3D-4C data from permanently installed systems in the North Sea;

o user-friendly fully-documented algorithms/software for PC cluster.

Datasets available:

o Valhall LoFS (Life of Field Seismic) 3D-4C data, North Sea;

o BG 4C data

o Shenli 3D-3C data, Yellow River Delta