Through Casing Formation Resistivity (TCFR)

GOWell’s Through Casing Formation Resistivity Tool (TCFR) provides deep-reading resistivity measurement behind steel casing. TCFR’s enhanced hardware and design brings improved operational efficiency.

The tool injects a current that travels up and down the casing before returning to a return electrode. While most of the current remains in the casing, a very small portion gets into the formation. Specially designed electrodes measure the nano-voltage difference created by this leaked current, and that difference is proportional to the formation conductivity.

A perfect contact between the tool and the casing is essential for the very sensitive measurements. The adaptive carbide electrodes are designed to scrape through small amounts of casing scale, corrosion, paraffin, etc. to establish good electrical contact. Usually, no well clean out or paraffin cutting is required.


TCFR Log Example 1




  • Primary Formation evaluation in cased hole
  • Monitoring of gas-oil-water contacts
  • Re-evaluation of reservoir saturation 
  • Identify shallow gas 
  • Water injection status evaluation
  • Detection and evaluation of bypassed hydrocarbons


  • Stationary measurements taken to improve signal-to-noise ratio
  • Two transmitters and four receivers
  • Strong hydraulic telescopic electrodes used to sustain electrical contact 
  • Reduces costs in well cleaning and scraping operations
  • Suitable for use in highly deviated wells
  • String includes GR and CCL for ease of correlation
  • Can operate with any borehole fluids