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MID-4 Electro-Magnetic Defectoscope – Thickness Gauge for Multi-String Operations


Casing string and tubing integrity monitoring in killed and non-killed oil and gas wells of multi-string structure


In newly drilled wells MID-4 tool is used for monitoring:   

  • well design up to five casing barriers evaluation   
  • compliance with the project of casing string set point with different diameters and wall thickness       
  • liner setting interval
  • casing integrity and degree of wear during tool operation

In operating wells the MID-4 tool makes it possible to determine:

  • perforation intervals
  • location of through defects
  • parting of casing in four-string structure
  • actual installation intervals of sealing patches 
  • actual installation depth of casing packers, etc     
  • well design up to five casing strings
  • corrosion intervals and degree of casing string wear    
  • intervals of casing defects for repair
  • thickness of the 1st, 2nd, 3rd, and 4th columns

The tool includes 3 probes of defectoscope-thickness gauge, highly sensitive temperature sensor, gamma-ray and pressure sensors.


Max.diameter of the investigated pipes, mm исследуемых труб, мм508
Number of investigated pipes1; 2; 3; 4
Min.diameter of the investigated pipe, mm60 thickness of four barriers, mm50,8
Measurement accuracy of pipe wall thickness, mm
first barrier
second barrier
third barrier
fourth barrier

0,15 times the barrier thickness
0,2 times the barrier thickness
Min.length of a defect “crack” type along the pipe axis, mm
single pipe
second pipe
third barrier
fourth barrier

1/12 of the perimeter
1/4 of the perimeter
1/3 of the perimeter
1/2 of the perimeter
Min.length of a defect “transverse crack” type for a single pipe1/7 of the perimeter
Temperature sensor resolution, °С0,01
Time constant of the thermometer, sec.0,5
Operation temperature, °С-10 to 150
Max.temperature rating, MPa100
Overall dimensions of tool, mm:
     - diameter / length

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