Tenzorgeo Ltd

Background seismic vibrations are present at any given point in the geological environment. Their sources are processes that cause deformation of the Earth structure. These processes occur both on the surface and inside the Earth. If we construct data processing so as to extract vertical-directed longitudinal waves from this continuous seismic background noise, we can obtain their spectral characteristic, the structure of which will reflect the amplitude-frequency characteristic of the medium at the observation point. High-sensitivity low-frequency three-component devices, with ultra low level of intrinsic noise, are used to register background seismic vibrations. Such seismometers are 10-100 times more sensitive than standard seismic equipment and therefore can reliably record low-frequency signals. The oil and gas deposit in the geological environment will absorb the background vibrations. Absorption in the oil and gas reservoir is frequency-dependent and reaches the highest values at low frequencies (1-5 Hz). This is related to the frequency dependence of the forces of viscous internal friction between the fluid and the frame of the reservoir. Absorption reduces the interference effect from the boundaries of the oil and gas reservoir and causes abnormal reflection in the low-frequency range. Anomalous reflection from the oil and gas deposit leads to a change in the AFC of the medium above the reservoir. Therefore, analyzing the spectra in the low-frequency range, one can draw conclusions about the presence of hydrocarbons in the environment.