sTEM (TEM shallow modification)

SIGMA-GEO offers innovative solutions in the field of shallow research using the sTEM (depth up to 500-600 m).

About technology

sTEM is a transient electromagnetic method (TEM) in the near field zone in a shallow modification - method with a pulse-controlled source, based on the study of the transient field, which is excited when the current in the source changes.

 
Shallow soundings of the TEM allow a more detailed study of the upper part of the section compared to “deep” TEM due to the greater locality of the research and the characteristics of the equipment.

Geological objectives solved by the sTEM method

  • Groundwater (for population needs)
  • Search for water (for the needs of the oil and gas industry)
  • Study of permafrost rock
  • Orebody geophysics
  • Engineering-geological research
  
  • Geoenvironmental research

 

Methods of field work, equipment and facilities

Generally, the design of the sTEM survey network has been carried out using a network of seismic profiles, any roads available in the area are also taken into account: rural, forest, logging and others.

The parameters of the sTEM observation technique may vary depending on the characteristics of the experimental site and the geological tasks, but most often three-spaced (less often two-spaced) station with square transmitter and receiving loops are used, and the current strength in the transmitter loop reaches 30 A.

 

 

 

The use of coaxially-spaced stations makes it possible to identify effects such as induction-induced polarization and magnetic lag and take them into account at the interpretation stage.

When carrying out shallow (sTEM) soundings uses the FastSnap software and hardware complex, which has proven itself in work in various geological and geographical conditions.

Сurrent switch 
FastSnap CTU-30 		 Measurement module
FastSnap RXU-V3

 

sTEM field work does not require significant resources. Optimal configuration of a fielded party:

  • 6 people
  • 1 set of equipment
  • 1 unit of transport equipment

 

The average productivity of one fielded party per month is more than 900 physical points of the sTEM.

 

In-office studies

Electromagnetic data processing is carried out in the modern TEM-Processing program, which includes statistical and robust signal accumulation methods, as well as a set of specialized frequency filtering algorithms.
Quantitative interpretation of signals is performed in the Model software package, based on algorithms for solving forward and inverse problems developed at the Institute of Petroleum Geology and Geophysics SB RAS.

Quality control

According to the requirements of the Electrical Prospecting Instructions, control observations are carried out without fail in the amount of 5% of the total number of planned observations. However, for additional control at both the field and in-office stages of work, quality assessment is performed using advanced software:

  • EMQC - a comprehensive system for assessing data quality, which allows to automatically perform quality control of the material and quickly identify data complicated by electromagnetic interference, anomalous and substandard curves based on quantitative QC quality indicators.
  • EMIQ - specialized software for assessing the quality of interpretation of sTEM and TEM materials.

 

SIGMA-GEO work experience using the sTEM method

  • More than 9,000 km2 have been completed across Russia
  • More than 190,000 physical observations (29,000 lin km) of the sTEM
  • Work using the sTEM method has been tested in various climatic, geographical and geological conditions; the effectiveness of the predictions has been repeatedly confirmed by drilling