Coil Tubing

Coil Tubing refers to a very long metal pipe, normally 1 to 3.25” in diameter which is supplied spooled on a large reel. It is used for interventions in oil and gas wells and sometimes as production tubing in depleted gas wells. Coiled tubing is often used to carry out operation similar to wire lining. The main benefits over wireline are the ability to pump chemicals though the coil and the ability to push it into the hole rather than relying on gravity. Pumping can be fairly self-contained, almost a closed system, since the tube is continuous instead of jointed pipe.

For off shore operation, the ‘foot print’ for a coiled tubing operation is generally larger than a wireline spread, which can limit the number of installations where coiled tubing can be performed and make the operation costlier. A coiled tubing operation is normally performed through the drilling derrick on the oil platform, which is used to support the surface equipment, although on platforms with no drilling facilities a self-supporting tower can be used instead.

The tool string at the bottom of the coil is often called the bottom hole assembly (BHA). It can range from something as simple as jetting nozzle, for jobs involving pumping chemicals or cement thought the coil, to a large string of logging tools, depending on the operations.