India’s Hydrocarbon Outlook 2024 122 A Report on Exploration & Production Activities Figure 4.3: Map Showing Regional GDE MAP covering Mahanadi, KG and Cauvery Advanced Reprocessing of legacy 3D seismic data by operators The legacy processing of vintage 3D data does not meet controlled amplitude and controlled phase (CACP) processing requirements in some of the potentially prospective offshore basins in the east coast, viz., KG and Cauvery basin. Other concerns in legacy product include low S/N in the near stack, residual multiple noise, and misalignment between the near and far stacks inhibiting reliable AVO analysis. Therefore, there is a significant value in reprocessing and merging vintage 3D data volumes with latest processing algorithms to achieve better imaging preserving amplitude and phases for more accurate AVO interpretation. In the below instance, an international operator carried out reprocessing/merging of three contiguous vintage 3D seismic surveys in the deepwater offshore area of Cauvery Basin with the objectives 1) To reduce velocity uncertainty through the construction of a high-quality anisotropic PSDM velocity model incorporating; well calibration, tomography & Full Waveform Inversion (FWI) to enhance complex imaging and address residual gather moveout. 2) To improve gather and stack quality through broadband processing. The reprocessing resulted in significant improvement in imaging enabling quantitative amplitude interpretation over a much larger area for prospectivity evaluation. The result clearly demonstrates the opportunity in reprocessing of vintage raw data for amplitude interpretation, de-risking of plays/prospect and improving the overall prospectivity of east coast basins.
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