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Pruessmann J.,TEEC | Eisenberg-Klein G.,TEEC
76th EAGE Conference and Exhibition 2014, Workshops | Year: 2014

Wide azimuth (WAZ) marine seismic data commonly provide an enhanced but varying coverage in azimuth-offset domain, which decreases towards crossline azimuths and near-offsets. The variable offset-azimuth illumination of WAZ data is commonly exploited in prestack depth migration in order to resolve complex subsurface structures, but often leads to amplitude footprints due to the variation, that disturb AVO and AVAZ analyses. An interpolation in azimuth-offset domain based on the CRS technique may largely reduce these footprints, and effectively precondition the data for amplitude studies. The CRS, or Common Reflection Surface method is essentially a multi-parameter stacking method that is used here to regularize and interpolate the data in one step. A regular coverage in CMP-offset-azimuth is thus achieved in most part of the data. Subsequent azimuth-dependent prestack time migration provides high resolution images at low migration noise, with strongly reduced footprints and well-preserved amplitude trends as a basis for subsequent amplitude studies.


Pruessmann J.,TEEC | Gierse G.,TEEC | Harms G.,RWE AG | Vosberg H.,RWE AG
SEG Technical Program Expanded Abstracts | Year: 2011

The Common-Reflection-Surface (CRS) method may improve seismic processing beyond imaging, e.g. in an enhanced Amplitude Versus Offset (AVO) analysis. Various applications have shown that the more realistic subsurface assumptions, and the increased fold of the CRS imaging allow to extend AVO analysis into noise zones and to deep targets with low signal quality. Extreme fluctuations of AVO parameters are removed, and AVO anomalies are enhanced. The CRS method assumes subsurface reflector elements with dip and curvature, which implies large-fold stacking surfaces extending both across offset, and across neighboring CMP locations. The extension across neighboring CMPs defines a CRS gather at the central CMP location, comprising data from a multitude of traces. The CRS moveout correction compensates for the local dip across these neighboring CMPs, thus contrasting to conventional AVO super-gathers based on NMO correction that collect dipping events horizontally at varying phase. The presented case studies show that CRS-AVO attribute stacks are produced with a much higher signal-to-noise ratio from CRS gathers than from CMP gathers in conventional AVO. The CRS-AVO attribute sections clearly distinguish anomalies at known or expected gas-bearing reservoirs. Cross-plots of CRS-AVO attributes show a better separation of anomalous zones which may be classified in order to identify top and base of hydrocarbon deposits. © 2011 Society of Exploration Geophysicists.


Gierse G.,TEEC | Schuenemann E.,TEEC | Tessmer E.,University of Hamburg | Ballesteros R.,Geoprocesados
SEG Technical Program Expanded Abstracts | Year: 2011

Depth migration based on wave-equation algorithms have been established as standard tools in the processing of reflection seismic data. Reverse time migration (RTM) provides depth images of high accuracy but may be hampered by low data quality, and noise contamination. In such cases the combination of RTM with prestack data preconditioning by the Common-Reflection-Surface (CRS) technique can improve the imaging result. While previous CRS strategies for prestack data mapping regularized CMP and offset coverage for an improved Kirchhoff migration, a new CRS strategy provides so-called CRS shot gathers that preserve the original shot geometry while providing a strong noise suppression. These CRS shot gathers are well suited as input of shot based depth migration algorithms like one-way wave equation and reverse time migration (RTM). These state-of-the-art migration techniques benefit from the strong signal-to-noise ratio of CRS shot gathers. The reverse time migrated shot gathers in offset and angle domain offer new possibilities for velocity analysis in complex geologic structures. © 2011 Society of Exploration Geophysicists.


Schuenemann E.,TEEC | Gierse G.,TEEC | Tessmer E.,University of Hamburg | Ballesteros R.,Geoprocesados | Salazar H.,PEMEX
73rd European Association of Geoscientists and Engineers Conference and Exhibition 2011: Unconventional Resources and the Role of Technology. Incorporating SPE EUROPEC 2011 | Year: 2011

Depth migration based on wave-equation algorithms have been established as standard tools in the processing of reflection seismic data. Reverse time migration (RTM) provides depth images of high accuracy but may be hampered by low data quality, and noise contamination. In such cases the combination of RTM with prestack data preconditioning by the Common-Reflection-Surface (CRS) technique can improve the imaging result. While previous CRS strategies for prestack data mapping regularized CMP and offset coverage for an improved Kirchhoff migration, a new CRS strategy now provides so-called CRS shot gathers that preserve the original shot geometry and provide a strong noise suppression. These CRS shot gathers are well suited as input for shot based depth migration algorithms like one-way wave equation, and RTM. These state-of-the-art migration techniques benefit from the increased signal-to-noise ratio of CRS shot gathers. The reverse-time migrated shot gathers in offset and angle domain offer new possibilities for velocity analysis in complex geologic structures.


Pruessmann J.,TEEC | Bergmann P.,German Research Center for Geosciences | Gierse G.,TEEC | Lippmann A.,TEEC | Lueth S.,German Research Center for Geosciences
74th European Association of Geoscientists and Engineers Conference and Exhibition 2012 Incorporating SPE EUROPEC 2012: Responsibly Securing Natural Resources | Year: 2012

The Common Reflection Surface, or CRS technique offers a comprehensive workflow for improving seismic processing, imaging, and reservoir characterisation in time and depth, which has been demonstrated in a project of geological CO2 storage at the Ketzin site in Eastern Germany. In applications to the 3D seismic baseline data that was acquired before CO2 injection, the results of the CRS time processing chain are compared to a previous conventional processing. The CRS noise suppression and regularization in the prestack data result in the so-called CRS gathers where acquisition related data gaps and fold variation are compensated for using the lateral event continuation of the CRS method. Both, the data reconstruction and the enhanced prestack signal quality lead to an increased resolution of the subsurface image, and strongly improve the tie to the well data. In the mapping of shallow gas at extremely low fold at this time level, CRS-based AVO resolves a well defined outline and inner structure of the gas zone, and clearly discriminates high-amplitude events outside the gas zone. The CRS technique thus proves to be a versatile tool for improved structural assessment and reservoir monitoring in both, storage and exploration projects.

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