How Does Coiled Tubing Work? First, a coiled tubing unit (CTU) central to CT surface operations consists of a reel that holds a continuous length of flexible steel pipe. After that, the tubing is deployed downhole by spooling it off the reel and guiding it through a gooseneck, which directs the CT downward to an injector head. It becomes straight before it enters the borehole. Right after the end of the operation, the flexible tubing is taken out of the well and spooled back onto the reel using