CRS Stack – an alternative implementation?

CRS Stack –an alternative implementation? S. Dümmong, C. Vanelle and D. Gajewski University of Hamburg

Motivation • Test an alternative search scheme • Model independent meaning of the stacking parameters • Still valid for the extension to other stacking cases (offset, converted waves, anisotropy)

Outline • Introduction • Alternative CRS parametrization • Synthetic data example • Real data example • Conclusions and outlook

Introduction • Original CRS stacking concept for the 2D case: • Parametrization in midpoint/half offset coordinates • Fitting hyperbolic surfaces to the data • Defined through three parameters (α, Knip, Kn) • More traces contribute to one CMP position • 3D optimization problem • Split into three 1D optimizations

Introduction

Alternative CRS parametrization • Alternative formulation: • Shot- and receiver coordinates • Three stacking parameters: first and second derivatives of the traveltime • Traveltime formula after Vanelle and Gajewski (2002) • Model independent meaning of the stacking parameters is used

Alternative CRS parametrization • Extension to offset stacking in the original parametrization: • Combinations of parameters have to be determined • Due to the parametrization in midpoint and half offset coordinates • Physical interpretation/meaning is lost • In this alternative parametrization: • Same parameters can be used • Also valid for anisotropy and converted waves

Alternative CRS parametrization • 3D optimization problem: • Split into one 1D and one 2D optimization • Optimizations are performed in special subsets of the data (CMP gather, CR/CS gather) • Parameters are determined in prestack data

Alternative CRS parametrization Prestack Data CR/CS Stack 2D optimization Automatic CMP Stack 1D optimization CRS Stack optionally local 3D optimization

Synthetic data example • Data set: Sigsbee 2a

Synthetic data example

Real data example • Data set: BGR99-07

Real data example

Conclusions and outlook • Alternative CRS Stack implementation was presented: • Alternative optimization scheme • All parameters are determined in prestack data domain • Model indenpendent meaning of the stacking parameters • Better images in the original parametrization: • Higher S/N ratio in the subsets of the data (ZO section from the Automatic CMP Stack)

Conclusions and outlook • Sections weighted with semblance show almost the same image quality in both parametrizations • Alternative implementation could be improved: • Conflicting dip handling • Optimize the searching scheme in the 2D optimization • Extension to offset stacking is straightforward

Acknowledgements • Thanks for the support to: • Wave Inversion Technology (WIT) Consortium • University of Hamburg • Thanks for the attention

CRS Stack – an alternative implementation?