关键词:  岩屑床, 当量循环密度, 控压钻井, 反循环, 长水平段, 延伸极限, 页岩气

Abstract: Long horizontal well drilling is often challenged by poor hole cleaning, drag torque, or even sticking is often observed, which will restrict the extension of horizontal intervals through narrow mud window formations and thus more casing strings have to be run. A reverse circulation drilling technology with a dual drill string by Reelwell is introduced herein for above mentioned challenges. Its principle, tools, drilling fluid used and field test data analysis are presented. The test in a shallow horizontal well has verified that the new technology can realise MPD while maintaining the hydrostatic pressure in the borehole. The torque and drag can be reduced due to the drill string buoyancy. And efficient hole cleaning can be obtained at low flow rates due to return flow inside the dual drill string.

Key words:  , cuttings bed, ECD, MPD, reverse circulation, long horizontal well, extended-reach drilling, shale gas