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CPC Subgroup
E21B 47/0228

using electromagnetic energy or detectors therefor

Full Title

Survey of boreholes or wells (monitoring pressure or flow of drilling fluid E21B21/08) > Determining slope or direction > of the borehole, e.g. using geomagnetism > using electromagnetic energy or detectors therefor

1 direct subcode

Child Classifications

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  • E21B 47/0232 at least one of the energy sources or one of the detectors being located on or above the ground surface

Top Applicants

Top 10 applicants by patent filingsfor class E21, 2013–2023, worldwide · Source: EPO PATSTAT

  1. HALLIBURTON ENERGY SERVICES GROUP US 27,652
  2. SAUDI ARABIAN OIL COMPANY SA 7,755
  3. PETROCHINA COMPANY 7,025
  4. BAKER HUGHES US 6,589
  5. SCHLUMBERGER TECHNOLOGY US 6,151
  6. SINOPEC (CHINA PETROCHEMICAL CORPORATION) 4,443
  7. SCHLUMBERGER TECHNOLOGY NL 4,255
  8. CNPC (CHINA NATIONAL PETROLEUM CORPORATION) 3,991
  9. SERVICES PETROLIERS SCHLUMBERGER FR 3,300
  10. SCHLUMBERGER CANADA CA 3,086