Patent ID: 6446737
Filing Date: 2002-09-10
Classification: E21B

Abstract:
A drill string for use in drilling an oilfield wellbore, comprising;a. a tubing extending from a surface location to a certain depth in said wellbore; b. a drilling assembly having a drill bit at a bottom end thereof for drilling said oilfield wellbore, said drilling assembly coupled to said tubing; and c. a rotational device in the drill string at a predetermined distance uphole of said drill bit, said rotational device rotating a section of said drill string downhole of said rotational device (â€œlower sectionâ€ ) relative to a drill string section (â€œupper sectionâ€ ) uphole of said rotational device to reduce static friction in said lower section during drilling of said oilfield wellbore, wherein the rotational device comprises; (i) an engagement device which allows rotation of said lower section relative to said upper section; and (ii) a rotational power unit operatively coupled to said engagement device, said power unit engaging with said engagement device to rotate said lower section.