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University of Durham (2004)

Static problems due to sand dunes in NC151, Western Libya

Ushah, Abdurrazag M. Ali

Titre : Static problems due to sand dunes in NC151, Western Libya

Auteur : Ushah, Abdurrazag M. Ali

Université de soutenance : University of Durham

Grade : Doctor of Philosophy (Ph.D.) : 2004

Résumé
This thesis deals with static problems on seismic reflection profiles over sand dunes in concession NC151 in western Libya. Two methods of computing field statics have been implemented and the results are compared. Two seismic lines of 38.5 km total length that crossed over sand dunes were processed in Durham using ProMAX software for each set of field statics. The refraction method statics are estimated as half the plus time at each station and then adjusted to uphole data with linear interpolation, yielded a significant improvement over the conventional method previously used, which relies soley on interpolation of the near-surface velocity structure between upholes. The maximum power autostatics method was chosen from several residual statics methods that are available in the ProMAX package. Two iterations of maximum power autostatics and velocity analysis followed by non-surface-consistent trim statics improved the final stacked sections. Part of a third seismic line of 13 km length that was located between sand dunes, and which tied the other two lines, was processed with the same parameters. The differences in source and receiver field statics between this line and the other two lines at the intersections were negligible. However, a fault on this line caused a problem for the refraction method of computing field statics. A simple method of interpolating field statics between upholes over this part of the line was used instead.

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