Higher Vibrator Hydraulic Force for Improved High Frequency Generation

Summary For conventional deep seismic with heavy vibrators, the traditionally used sweeps had an 8-80 Hz bandwidth. Extending the bandwidth to include lower frequencies has been largely addressed over the past five years and sweeps are now starting as low as 1.5 Hz in Middle East surveys. However, generating high frequencies is essential for improving the vertical resolution and imaging thin layers. Their use remains limited until now as their recording is highly ground-dependent; moreover, several physical vibrator limitations restrain the generation of high quality high frequencies. This abstract presents how the vibrator behaves as the sweep frequencies increase, and how the phase shift between the reaction mass and the base plate makes the vibrator reach its hydraulic maximum output. A practical solution illustrated by field tests is then proposed: by increasing the vibrator hydraulic capability, an extra sweep bandwidth can be effectively generated and the conventional 80 Hz high-end sweep frequency extended.