Duhn Oil Tool, Inc.

Duhn Industries

William D Chapman

Rex E Duhn

Jay C Duhn

This invention relates to a two-piece drilling flange which allows for the full engagement of a conventional casing head external thread (8-round thread) reducing thread wear. The two-piece drilling flange incorporates a flange-bushing piece and a drilling-flange piece. The flange-bushing piece is hand tightened on the 8-round thread so that the casing head end face protrudes beyond the bushing. The drilling-flange piece is threaded onto the flange-bushing piece until a highly reliable elastomeric radial seal makes tight contact with the casing head end face. The drilling-flange piece is then further tightened, exerting an upward force on the flange-bushing piece, ensuring the full engagement of the casing head 8-round thread by the flange-bushing piece internal thread. This tight thread fit reduces thread wear by preventing destructive movement between the threads, especially during the highly vibrating drilling process.

Two-piece drilling flange

A ground subsidence wellhead has a lower wellhead assembly mounted on the ground for supporting a casing in tension and an upper wellhead assembly threaded to the top of the casing and spaced from the lower wellhead assembly. The lower assembly has a casing head with aconical bowl for receiving a slip. The slip is wedged between the casing head and casing by compression springs acting between the casing head and the slip, and has asymmetrical teeth for engaging the casing to prevent downward, but allow upward, movement of the casing in the slip.

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Bakersfield, CA, United States of America

William D Chapman