Title:
Bottom hole pressure control in well drilling
United States Patent 2786652


Inventors:
Wells, Norman C.
Application Number:
US47634354A
Publication Date:
03/26/1957
Filing Date:
12/20/1954
Assignee:
Wells, Norman C.
Primary Class:
Other Classes:
175/38, 175/71, 175/206, 175/210, 175/212, 175/213, 175/215
International Classes:
E21B21/12
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