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Converted-wave Velocity Modeling Method of Ultra Deep Carbonate Reservoir in Western China
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 77th EAGE Conference and Exhibition 2015, Jun 2015, Volume 2015, p.1 - 5
Abstract
Converted-wave velocity modeling is very important in converted-wave PSTM. Based on the converted-wave data in western China, we proposed a velocity modeling approach for ultra deep carbonate reservoir. Firstly, the original converted-wave migration velocity volume was determined by migration velocity scanning after the effective stack velocity was obtained. Then the original P-S wave velocity ratio r0 was estimated based on well data and the comparison of PP and PS wave stack sections. Afterwards the CIP gathers were generated by PSTM using the original velocity and r0 volume. The gathers were processed to improve the signal-noise ratio and the four-parameters’ spectra were updated to flatten the events. It was migrated again using the updated four-parameters and then four parameters were updated again based on the new CIP gathers. The iterations were adapted several times until all events were flattened. In this velocity modeling approach, compared with using the stack velocity as the original velocity, it was more accurate to obtain the original velocity based on migration velocity scanning, and the follow-up iterations could converge faster. The special processing for CIP gathers also solved the poor focusing problem of four-parameters’ spectra in ultra deep carbonate reservoir, and improved the accuracy of updated velocity.