Applications

Geothermal Exploration

In volcanic settings, geothermal reservoirs are characterized by high temperature and permeability, usually leading to high resistivities. However, extensive clay alteration of the enclosing rocks results in low resistivities. The contrast of resistivity provides an excellent tool for identifying geothermal targets.

Magnetotellurics (MT) is the standard method for mapping the alteration cap and, via 3D inversion, the underlying reservoir. We have carried out geophysical surveys and interpreted the data on the majority of the world's geothermal prospects. Typically, these have been programs which have integrated MT, time domain electromagnetics (TDEM), and gravity data with available geochemical and geological data.

Mineral Exploration

Exploration for massive sulfides is carried out at shallow depths (a few hundred meters or less) using induced polorization (IP) or TDEM surveys. At greater depths, the only electromagnetic technique available is that of audio-magnetotellurics (AMT) or controlled source audio-magnetotelluric (CSAMT).

Over the past decade, improvements in acquisition hardware, processing algorithms, and interpretation software have led to increased reliability and reduced cost. These have made the AMT method a useful tool for mineral exploration, especially in large scale frontier exploration. It has become an effective tool for property assessment and in focusing exploration with controlled source techniques typically used in mineral exploration.

Oil and Gas Exploration

We provide cost-effective geophysical solutions in hostile environments, such as those characterized by complex thrust belt tectonics, shallow volcanics, outcropping carbonates, or sub-salt. In such environments, the conventional seismic methods often provide marginal results and new exploration approaches need to be defined.

To MT, the conditions which cause difficult seismic energy propagation are largely irrelevant and so the method readily images the resistivity of the sub-surface.

Ideal targets include resistive carbonate reservoirs below shale or flysch and clastic reservoirs below salt bodies. Integration of seismic, gravity, and MT leads to improved velocity-model building for outcropping carbonates, thrust sheets, sub-basalt, and sub-salt for seismic imaging, as well as to better resistivity estimates for MT interpretation. The integration process is performed by joint inversion for multi-parametric models or on an interactive basis.