REVERSE CIRCULATION APPARATUS AND METHODS FOR USING SAME

摘要

In one aspect, an apparatus for drilling a wellbore into an earth formation is disclosed, which apparatus, according to one embodiment, may include a drill string configured to be conveyed into a wellbore, wherein an annulus is formed between the drill string and a wellbore wall, a first flow device configured to circulate a first fluid from an annulus to a bore of the drill string, and a second flow device positioned downhole of the first flow device, the second flow device configured to circulate a second fluid from the bore of the drill string to the annulus.