See here for an introductory overview of EM technology.
Surface Electromagnetics Surveys
Gap GeoPhysics have a long history of delivering quality and efficient EM surveys. Gap GeoPhysics gains an advantage from our proprietary high power transmitters. The HPTX-70 was created for large fixed loop configurations. The MLTX-200 was developed as a mobile, yet high current transmitter, for moving loop configurations. Recently Gap GeoPak have created the IPTX-2500 - for IP surveys.
We offer three main techniques. Which technique represents the right choice for a survey depends on the geological conditions and the preferred choice of sensor.
1. Sub-Audio Magnetics : This technique uses a cesium-vapour sensor and collects both total magnetic field and transient EM responses from a moving survey. For larger survey areas, the system can be taken airborne - see HeliSAM.
2. SAMSON : Similar to SAM, except not as a moving survey, but rather using short (five minute) stations, for deeper ground penetration.
3. SMARTem24 : A powerful fast sampling 24 bit receiver system that can use a fluxgate, coil and/or other sensors.
Downhole Electromagnetic Surveys
Gap GeoPhysics's DHEM system consists of a 2km Auslog winch and DigiAtlantis 3 component B-field probe produced by ElectroMagnetic Imaging Technology (EMIT). When combined with Gap GeoPhysics’s HPTX-70 EM transmitters, it is the most powerful downhole EM system currently available. It is ideally suited to the detection of subtle or deep conductors. Contact us for more information.
To perform underground EM requires access to the right gear. A transmitter system needs to be able to run without generator - such as our high current MLTX-200, with the PS10LV as the power supply.
Our crews are well experienced with the requirements of underground work.