Infrasonic passive differential spectroscopy


Infrasonic passive seismic spectroscopy is a passive seismic low frequency technique used for mapping potential oil and gas hydrocarbon accumulations.
It is part of the geophysical techniques also known under the generic naming passive seismic which includes also passive seismic tomography and micro seismic monitoring for petroleum, gas, and geothermal applications. In a larger scale, passive seismic includes the Global Seismic Network earthquake monitoring.
Regarding petroleum and geothermal exploration, the effect of fluid distribution on P-wave propagation in partially saturated rocks is responsible for the low frequency reservoir-related wavefield absorption.
The high level of attenuation within the infrasonic bandwidth of the seismic field observed in natural oil-saturated porous media during the last years is the main responsible of the passive seismic wave field shifting within a low frequency range.
Pressure differences between regions with different fluid/solid properties induce frequency-dependency of the attenuation and velocity dispersion of the low frequency wave field.
Infrasonic passive seismic spectroscopy quantifies the absorption and the wave field dispersion within the low frequency bandwidth giving the most predominant areas linked with possible oil-saturated and porous media.
The low frequency seismic field is not usually reachable by the active seismic surveys being either the explosive waves mainly in the high frequency and the vibroseis currently built not to reach such a low frequencies.