TREA

William D. Chapman

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  • Bakersfield, CA, US
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Patents Grantslast 30 patents

  • Information Patent Grant

    Two-piece drilling flange
    • Patent number 5,611,398
    • Issue date Mar 18, 1997
    • Duhn Industries
    • Rex E. Duhn
    • E21 - EARTH DRILLING MINING
  • Information Patent Grant

    Ground subsiding wellhead
    • Patent number 4,974,676
    • Issue date Dec 4, 1990
    • Duhn Oil Tool, Inc.
    • Rex E. Duhn
    • E21 - EARTH DRILLING MINING