Harmonic distortion reduction on vibrators — Suppressing the supply pressure ripples

Abstract

Due to non‐linear effects, the ground‐force signal transmitted into the subsurface by vibrators is contaminated by harmonics. Hydraulic power supply pressure fluctuations contribute to the overall harmonic content of the vibrator output. Supply pressure ripple is rich in even harmonic distortion and strongly dominated by the 2nd harmonic. A new reaction mass design significantly reduces hydraulic supply fluctuations to provide a more constant supply pressure. Field‐testing of the new reaction mass system demonstrates a dramatic reduction of the harmonic distortion in the ground‐force signal output by the vibrator. Significant reduction of harmonic distortion in the ground‐force signal is achieved when the vibrator is on hard and uneven ground. Cavitations in the supply pressure, a long‐standing problem in vibrator mechanics, were almost completely eliminated.