To pump drilling fluid into the borehole through the drill-pipe and back up the annulus between the pipe and the wall of the hole to cease drilling but to maintain circulation for any reason. When closer inspection of the formation rock just encountered is desired, drilling is halted as circulation is continued to "bring bottoms up" (q.v.). circulate -to pass from one point throughout a system and back to the starting point. Drilling fluid circulates from the suction pit through the drill pipe to the bottom of the well and returns through the annulus.
