Objective
The main objective of the project is the assessment of innovative 3D prestack processing techniques aimed at improving the accuracy of 3D seismic depth images in terms of localization, spatial resolution and true amplitude reflectivity. Particular attention will be paid to improving the preprocessing methodology of 3D land seismic survey. Additional gain will be to provide some insight on the minimal trace density needed in order to preserve the accuracy of depth imaging and to promote the use of 3D borehole seismics for local structural interpretation. To secure the objective of the demonstration, the following partnership was set up : Institut Francais du Petrole, CGG, Delft University, ARMINES, POLIMI and Karlsruhe University.
Results concerning the qualification of the synthetic dataset:
- The initial Overthrust synthetic dataset was provided on tapes to the project, decimated to 50m between traces. "Classic Data Sets" were defined and constituted as subparts of this initial dataset of common interest for research application or benchmarks, small enough to be easily distributed, but still representattive of actual marine, land or VSP surveys. Their list is described on the SEG/EAEG 3D Modelling series #1, 1997.
- We found that the numerical accuracy and the model complexity was sufficient for our technical objectives. The sampling of traces to 50m is acceptable, because the limited frequency bandwith.
- It should be noted that the model present important near surface velocity anomalies, with rather high velocity, which can not be accounted by classic static corrections.
Results concerning prestack technologies:
- The two methods tested for trace or short interpolation (3D shot continuation and predictor error filter) are both satisfactory for 3D shot interpolation.
- The 3D tomographic inversion of refracted arrivals provides a generally acceptable refractor mapping for near surface velocity anomaly but fails to avoid serious distrosion after statics application. It appears that non consistent surface static are advisable.
- 3D preserved amplitude prestack depth migration (Ray-Born imaging) was applied to the dip shot line using a wide receiver patch: the main features were imaged with correct amplitudes, without significant footprint of the acquisition.
- 3D shot gather waveform imaging proved to be an efficient tool for prestack migration of the complex part of the model.
- An application of the theory of wave images for velocity model updating achieved on the zero-offset classic dataset.
- Tests on 3D velocity model verification using 3D Common Focus point GAther technology are in progress.
- 3D walk-away was migrated using true amplitude ray-Born algorithm. It was shown that the separation of upgoing and downgoing waves can be achieved by the migration algorithm.
Phase 0 : Selection and distribution of data
Phase 1 : Interpretation of 3D prestack data
Phase 2 : Near surface velocity corrections
Phase 3 : QC processing
Phase 4 : Prestack imaging
Phase 5 : Macro Model Verification
Phase 6 : VSP's interpretation
Phase 7 : Synthesis.
Topic(s)
Call for proposal
Data not availableFunding Scheme
DEM - Demonstration contractsCoordinator
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