Coiled Tubing Unit

Overview

A coiled tubing unit runs a continuous, jointless string of small-diameter steel tubing into a live well without killing it. Unlike jointed pipe, the tubing comes off a single large reel, so the unit can push it in and pull it out quickly and under pressure. That makes it the workhorse of well intervention: cleaning out fill, milling scale, placing chemicals, nitrogen-lifting a dead well, logging, and fishing for stuck tools. The whole spread, reel, injector, well-control stack and power supply, is mobile so it can rig up over a wellhead and move on.

Because the well stays pressurized throughout, the unit is built around a chain of pressure barriers between the open atmosphere and the formation.

How it works

The tubing is stored on the Tubing Reel, whose level wind spools it evenly and whose hydraulic motor pays it out under controlled tension. It feeds over the Gooseneck Guide, a roller arch that bends it down into the Injector Head. There two opposed gripper chains clamp the tubing and drive it into or out of the well, with a load cell reading tubing weight so the operator knows the downhole force.

Below the injector, the Stuffing Box packs around the moving tubing to hold well pressure, and the BOP Stack sits beneath it as the well-control barrier, with four rams that can grip, seal or shear the tubing in an emergency. All of these functions are powered from the Hydraulic Power Pack, whose hydraulic pump and valve bank feed the reel, injector and rams.

The operator works from the Control Cabin, driving the injector and reel with joysticks while a data display shows depth, weight, speed and pressures. The complete spread is carried on the Trailer / Skid, which levels and anchors the unit at the wellsite.