08151907 is referenced by 55 patents and cites 1171 patents.

A method for forming a subsurface wellbore is disclosed. The method includes operating a drilling string in a first direction of rotation. A first motor located near the end of the drilling string is operated in a direction of rotation opposite that of the drilling string. A drill bit is rotated using a second motor that is coupled to the first motor.

Title
Dual motor systems and non-rotating sensors for use in developing wellbores in subsurface formations
Application Number
12/422084
Publication Number
8151907 (B2)
Application Date
April 10, 2009
Publication Date
April 10, 2012
Inventor
Duncan Charles MacDonald
Houston
TX, US
Assignee
Shell Oil Company
TX, US
IPC
E21B 4/16
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