This kind of tool is easy to use,and it can lower the annular cyclic pressure loss efficiently in the barefoot interval and improve the drilling maneuverability in the case of narrow density windows.

Because carbonate rock in Carboniferous system which was main reservoirs develop many cracks that caused not only mud loss but also well kick,and had narrow safety density window of drilling fluid,first lost circulation then well blowout is easily to happened,so drilling fluid rheological property became as the important factor of affecting pressure balance in well.