Patent ID: 9022146
Filing Date: 2015-05-05
Classification: E21B

Abstract:
1. An apparatus for drilling a well bore in a formation, comprising: a drilling assembly configured to be conveyed into the wellbore by a drill string, wherein an annulus is formed between the drilling assembly and the wellbore; an isolator that isolates the annulus into an upper zone and a lower zone at a selected location uphole of a drill bit; a first flow device in the drill string uphole of the selected location, configured to flow a first fluid and a second portion of a second fluid in the drill string uphole; a second flow device positioned in the drill string downhole of the selected location, the second flow device configured to flow a first portion of the second fluid in the drill string to the drill bit; and a separator located at the drilling assembly between the first flow device and the second flow device and configured to direct the first fluid from the lower zone of the annulus to the first flow device, direct the second portion of the second fluid from the upper zone of the annulus to the first flow device, and direct the first portion of the second fluid from the upper zone of the annulus to the second flow device.