The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jan. 12, 1988
Filed:
Aug. 28, 1986
Applicant:
Inventor:
Robert B Stewart, Rijswijk, NL;
Assignee:
Shell Oil Company, Houston, TX (US);
Attorney:
Primary Examiner:
Int. Cl.
CPC ...
E21B / ;
U.S. Cl.
CPC ...
175 70 ; 175215 ;
Abstract
A method of drilling a borehole is provided using a drill bit coupled to the lower end of a pair of concentric drill pipes. During drilling a first low viscosity fluid, such as oil or water, is circulated through the pipes while a second fluid, such as a weighted viscosified mud, is kept stationary in the pipe/formation annulus.