Use and misuse of the nonlinear Vibroseis method for the acquisition of high resolution seismic data
The recent use of nonlinear Vibroseis (trademark of Continental Oil Co.) sweeps became possible with development of an electronics system to drive the vibrators in a nonlinear mode. This new electronics system allows the user to adjust both the vibrator amplitude and the rate of frequency change during the sweep. Nonlinear Vibroseis sweeps are now becoming popular for the acquisition of high resolution seismic data in the petroleum industry. However, nonlinear sweeps can seriously degrade seismic data when the amplitude and frequency controls are used incorrectly. The amplitude controls are used to overcome decoupling, ground roll, and vibrator/ground resonance problems. By suppressing the vibrator drive at the lower frequencies, the typical decoupling effect can be eliminated and the effect of the ground roll minimized. This permits the use of shorter geophone arrays that are more suitable for high resolution recording. In addition, the use of a lower amplitude sweep at the low end of the frequency range helps suppress vibrator/ground resonance. This reduces the large amplitude of the resonance frequency and allows the recording of the weaker high frequency signal. The ability to control the rate of frequency change during the sweep allows the user to recover an improved signal-to-noise ratio at the higher frequencies. In general, the sweep time is reduced in the lower frequencies and increased in the higher frequencies. The high percentage of sweep time at the high end of the frequency range results in an improved signal-to-noise ratio in the higher frequencies. However, the improper choice of the start and end sweep frequencies can result in recovered data that is actually poorer in signal-to-noise ratio than an equivalent linear sweep.
- Research Organization:
- Strat Seis Inc., Casper, WY
- OSTI ID:
- 6433040
- Report Number(s):
- CONF-8309274-
- Journal Information:
- Am. Assoc. Pet. Geol., Bull.; (United States), Journal Name: Am. Assoc. Pet. Geol., Bull.; (United States) Vol. 67:8; ISSN AAPGB
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
020200* -- Petroleum-- Reserves
Geology
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03 NATURAL GAS
030200 -- Natural Gas-- Reserves
Geology
& Exploration
EQUIPMENT
EXPLORATION
GEOLOGIC DEPOSITS
GEOPHYSICAL SURVEYS
INDUSTRY
MINERAL RESOURCES
PETROLEUM DEPOSITS
PETROLEUM INDUSTRY
RESOLUTION
RESOURCES
SEISMIC SURVEYS
SIGNAL-TO-NOISE RATIO
SURVEYS