Towed time domain electromagnetic and direct current electrical resistivity surveying

Groundwater Imaging Pty Ltd

This workshop will progress through all aspects of towed electromagnetic and direct current resistivity survey beginning with theory, through applications and to interpretation of results. All topics covered will also be applicable to, but not directly applied to, airbourne EM survey.

After quickly covering basic theory, exercises with generating sets of type curves for various layered geological models will be completed. By contrasting between forward models, the detectability limits of various apparatus will be established.

Limitations of equipment will be studied and the envelope of practical combinations of parameters assessed. The reasons why increasing various parameters beyond sensible limits fails to resolve any deeper will be demonstrated quantitatively.

The AgTEM Wallaby and AgTEM Wallaroo will be presented as case studies of towed time domain electromagnetic design.

Towed geo-electric streamers (HERBI) and mobile prong frames (Wombat) will be presented as case studies in direct current survey design.

Acquisition examples will be presented with emphasis on quality control assessment and identifying and dealing with various sources of noise.

Processing and modelling steps typically involved will be quickly covered.

Numerous examples of interpretation of datasets will reveal the geological complexities typically encountered with survey.

The workshop will finish with a challenge of design of a survey for an actual example site.