Low Frequency Optical Geophone

LSU Reference: 0517

Inventors:

Description:
  • An advanced geophone with extended low frequency response and improved sensitivity

Applications:
  • Measuring ground motion and vibration
  • Oil exploration - surface explorations and downhole explorations

Advantages:
  • Improved Seismic imaging of deep targets
  • Resonant frequencies below 0.5 Hz

Abstract: Geophones are instruments used for measuring ground motion and vibrations.  They are useful in oil exploration, mining, earthquake detection, machine vibration detection, and intrusion detection.  The majority of commercially available geophones use moving coil technology that produces analog signals proportional to the velocity motion.  Typical resonant frequencies are about 10 Hz.  However, the moving coil design limits the use of geophones in the lower frequency ranges, hence limiting the depth to which useful acoustic waves can penetrate.  The Low Frequency Optical Geophone developed at LSU is an advanced geophone with extended low frequency response and improved sensitivity.  The low frequency response of the geophones increases the resolution of data by broadening the frequency band , thus shortening the seismic wavelet.  Consequently, these geophones improve seismic imaging of deep targets.  Early prototypes have demonstrated resonant frequencies below 0.5 Hz, well below that of commercially available geophones.  While the novel geophone is intended to be used in surface explorations, it could also be used in downhole explorations.  Its high level of sensitivity provides an alternative for some downhole devices.  Furthermore, the geophone utilizes optical technology and is inherently digital; and maintains absolute accuracy.  These characteristics are believed to be highly useful particularly in oil exploration, as they would permit oil exploration at greater depths than currently feasible.

 

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