Passive Low Frequency Seismic (LFS) Technology

LFS technology is based on analysing spectral properties of low frequency between 0 – 10Hz of natural background seismic that changes above oil and gas deposits. LFS can be used to evaluate the spatial spread and distribution of CO2 in the reservoir. The technology has already been applied extensively to different geological and geographical situations, wherein the success ratio in solving tasks of hydrocarbon prospecting and exploration is over 85%. To date over 126 projects are completed with a total researched area of 1133.5 sq. km. Notably, in 95 wells utilising the LFS method, 81 wells confirmed the anticipated forecast with 28 wells roducing commercial hydrocarbons from the carbonate reservoirs, and 35 wells producing from terrigenous reservoirs.

Application

• The LFS technology is used to solve a wide range of geological and technological problems across a variety of operations. The technology is easily applied, cost-effective and environmentally friendly across a spectra of operations from the onshore to offshore domain.
• The method can be applied in prospecting, surveying and delineating the presence of hydrocarbons, optimising exploration targets and in production drilling. TenzorGEO have also leveraged on its high precision imaging capacity to offer a means of surveying CO2 plumes in subsurface storage operations.
• LFS offers flexibility where conventional practices would not be an option for example due to block size, active seismic waves, energy penetration issues, budget limitations, accessibility and/or environmental restrictions.

Physical Theory

• LFS is a passive seismic method that utilises abnormal low-frequency seismic reflection from hydrocarbon deposits or fluids such as CO2 which possess similar spectral properties. LFS is based on analysing the spectral properties of low-frequency P- waves in the range of 0.5 – 10 Hz. The waves are derived from passive or naturally occurring seismic signals, which are modified in the presence of oil and gas deposits.
• The occurrence of anomalous reflection from hydrocarbon deposits is associated with significant differences in the physical properties of hydrocarbons and water, such as compressibility, absorption, as well as due to the multiphase nature of the medium in the reservoir strata. Due to the mechanics of fluid-saturated, fractured and porous media, oil and gas reservoirs have high dispersion of velocity and high attenuation at low frequencies. A thin layer of oil/gas reservoir is characterised by high attenuation that reflects low-frequency P-waves, for this reason, it transforms the Amplitude-Frequency Characteristic of the media into an observational point in which TenzorGEO’s highly sensitive equipment can identify. This makes it possible to identify oil and gas deposits using observations from the surface by highly sensitive low-frequency equipment and the appropriate processing and interpretation software.
• The effect of spectral differences within hydrocarbons has been proven and traced in various regions the world over within a variety of geological and geophysical settings.