Pushing Vibroseis VSP Bandwidth Towards Low and High Frequencies

Seismic vibrators are commonly used for land vertical seismic profile (VSP) surveys. However, with most conventional vibrators, due to physical limitations in vibrator mechanical and hydraulic systems, the frequency bandwidth of vibrator ground-force output is limited, thereby degrading the VSP data quality. Acquiring broadband VSP data using Vibroseis techniques becomes very challenge. This paper attempts to address these problems with a new designed small vibrator. Experimental test shows that this vibrator is able to stably sweep up to 400 Hz. Downhole results demonstrate that this new designed small vibrator offers a measurable force-energy penetration. At the depth of 2700 ft (824 m), signal frequencies from 2 Hz up to 300 Hz can be seen. At the depth of 7500 ft (2288 m), a force-energy up to 150 Hz can still be observed.