Type of resources
Seismic reflection method is based on the propagation of seismic waves inside the earth. This method analyzes the reflected waves which are generated on or near the surface by a seismic source, travel down into the ground, reflect at a discontinuity (density and velocity contrast) and travel back up to the ground surface. Digital processing of seismic reflection data offers the opportunity to create cross-sectional images of the subsurface (seismic reflection section) showing the amplitude of the reflected wave at the correct horizontal and depth coordinate of the reflection point.
The Magnetotelluric method (MT) uses natural electromagnetic fields (electrical storms, ionosferic currents) as a source to study subsoil structure. Simultaneous recording of the horizontal electric and magnetic field variations on earth surface allows to determine the electrical resistivity variation as a function of the frequency (depth). Frequency band for MT data ranges from 0.001 Hz to 100 Hz that makes it possible to study depths of up to hundreds of km. For shallow studies (around 1 km investigation depth), control source audiomagnetotellurics method (CSAMT) or audiomagnetotellurics methods (AMT) are required. Frequency band in this type of studies ranges from 1 Hz to 100 KHz.
This method puts emphasis on the measurement of anomalies of the Earth's magnetic field, caused by the presence of reservoirs or structures on the subsurface. This technique allows to assess changes of nT in the Earth's magnetic field caused by the presence of some minerals. Those minerals are characterized by high magnetic susceptibility such as the magnetite.
Measuring and analyzing earth's gravitational field at the surface is one of the main tools to study the structure and composition of the Earth. The gravity method helps Geology in describing subsoil lithological variation based on density anomalies.
Borehole geophysical logging techniques are based on measuring and recording continuously the physical properties of interest along a borehole using different probes. Analysis of the correlation between the different records (logs) allows to characterize lithological section and formation fluids.
Vertical Electrical Sounding (VES) is a electrical resistivity method that involves injecting current into the earth and measuring the potential difference between a pair of points. In this way, apparent resistivity of the subsoil as a function of depth can be obtained. VES technique can be applied to a wide range of studies with a maximum investigation depth of about 200 m depending on the acquisition system.
Seismic refraction method is based on analyzing the travel times of waves refracted under the critical angle on subsoil interfaces (velocity contrasts). Seismic energy is radiated downwards into the ground from a seismic source on or near the ground surface (e.g. weight drop, explosives,etc.), critically refracted at the interface travelling along it and radiated back to the surface. Observed refracted waves travel-times versus distance are converted into seismic velocity cross-sections of the subsurface.