Expert Geophysics Limited specializes in airborne geophysical surveys worldwide with advanced electromagnetic systems:
Mobile MagnetoTellurics (MobileMT) is the most advanced generation of airborne AFMAG technology. MobileMT is the only system proven to deliver geoelectrical information from near-surface to greater than 1 km depth with high spatial resolution.
MobileMT technology utilizes naturally occurring electromagnetic fields in the frequency range of 25 Hz – 20,000 Hz. This technology is the product of extensive experience in developing equipment and signal/data processing algorithms for natural electromagnetic fields measurement. MobileMT combines the latest advances in electronics, airborne system design and sophisticated signal processing techniques to provide unmatched capabilities in the current frontiers of geophysical surveying.
What is Mobile MT?
“Stationary Magnetotellurics (MT) is a long-established electromagnetic geophysical method which provides accurate sub-surface data for reliable geological interpretations. MT measures the earths’ subsurface electrical conductivity using the natural geomagnetic and geoelectric field variations in the earth. MT utilizes the electrical fields generated by lightning discharges from thunderstorms that propagate through the sub-surface. MT is akin to conventional resistivity and electromagnetic surveys but incorporates magnetic fields to further help determine electrical heterogeneities between the earth and the audio frequencies. This technology has proven superior for identifying geological features of interest rather than conventional electromagnetic methods.
Mobile MT remains at the forefront of emerging exploration geophysical technologies. The “mobile” aspect of magnetotellurics, with data acquisition being possible with helicopter support, is a development which is proving to be a significant evolutionary shift in airborne geophysical methodologies.” James Sykes, CEO and President of Baselode Energy.
An airborne bird, towed by a helicopter, measures variations of the magnetic field, while a ground station measures variations of the electric field. The ratio of the magnetic and electric field magnitudes components provides with the parameter of apparent conductivity in selected bands of frequencies. The advanced noise processing techniques employed at both analogue electronic and digital signal processing levels ensures high data quality even for low natural EM fields. A cesium-vapor magnetometer is used for recording of the total magnetic field. The lightweight, aerodynamic bird is ideal for conducting surveys using small helicopters in a cost-efficient manner. See, please, details here.
MobileMT is not only broadband EM natural fields, but also EM-VLF signals and a high-quality magnetic field that is not distorted by any nearby transmitting fields. The VLF signals are received by the same 3 orthogonal MobileMT coils and recorded independently from up to four VLF stations. VLF data is a good complement to the wide range of the MobileMT system depth of investigation and provides additional shallow, high-resolution information. The example below is from the Shadow uranium exploration project, Baselode Energy.
MobileMT takeoff
TargetEM, a time-domain system for searching and precise targeting discrete conductors and for differentiating contrast stratigraphy in the depth range of hundreds of meters.
The TargetEM system is designed to provide VLF and AFMAG data along with time-domain EM data.
mTEM, a time-domain system for detail near surface investigations. mTEM system advantages: – Small footprint and high base frequency enable very high spatial resolution; – Detail subsurface geoelectric characterization; – Designed to work in areas with industrial electromagnetic noise (powerlines).
Saudi Aramco earns recognition for exploration and water management technologies with help of EGL’s airborne mTEM system:
Airborne Magnetometer System. The airborne magnetometer is a state-of-the-art system developed by EGL. It utilizes a Geometrics G822A or Scintrex CB-3 cesium magnetometer sensor, installed in the separate towed-bird and the high accuracy Larmor frequency counter developed. Magnetometry is combined with all electromagnetic systems, as well as used separately.
Gamma spectrometry – A Radiation Solutions Airborne Gamma Ray Spectrometer RS-500, with a sampling interval of 1.0 second. The RS-500 Series gamma-ray spectrometer is the “Gold Standard” in airborne instrumentation for the detection and measurement of low level radiation from both naturally occurring and man-made sources. The system is self-calibrating and will be configured to 16.8l NaI (Tl) volume detector array. Spectra stabilization: real time automatic corrections on radio nuclei: Th, U, K. No implanted sources. Time to stabilization: on the ground usually less than 1 minute and in the air usually less than 4 minutes.
RS-500 Advanced digital gamma-ray Spectrometer
1024 channel resoultion
5 large volume NaI(TI) detectors configured to operate as 4 downward looking detectors (16L) and one upward looking detector (4L)
1 Hz data output
The gamma-ray spectrometer can be used together with a magnetometer and electromagnetic systems.
Airborne geophysics data processing and interpretation. We don’t just measure physical fields, we provide full data processing, imaging, and interpretation services; conduct detail analysis of the collected data; supply resistivity-depth products – models, sections, depth slices; integrate information and interpret it.
