Coiled Tubing :: coil tube coiled tubing

First of all, what in the world is coiled tubing? Otherwise referred to as CT, coiled tubing is a manufactured product used in field operations such as well service, workover applications (petroleum industry well work), and drilling and completion applications. Just as is sounds, CT is essentially a continuous tube with a diameter of .75 inches up to 4.5 inches that is reeled onto a spool, which has a core diameter of approximately eight to twelve feet. The tubing is made from rolling strip metal, usually a carbon based steel, into cylindrical form and weld along its entire length. The longitudinal weld is made using a high-frequency induction electrical resistance method. The welding process produces a small amount of weld flash on both the inside and outside of the tube. This is removed from the outside diameter of the tube after welding by a carbide cutting tool contoured to the diameter of the tube being produced. The weld vein is instantly re-heated to re-crystallize the w elded zone to match the grain composition of the base metal. So in other words, you have this extremely long steel tubing coiled up like a garden hose on reel without any visible end welds. The entire length is non-destructively inspected, then gauged and hydrostatically tested to assure the pipe meets customer specifications prior to shipment. A single spool can carry an average length of approximately 15,000 feet but have been fabricated up to 30,000 feet depending on the diameter of the tubing. Tubing continuously wraps and unwraps over its spool and over the tubing directional arch (â€Å"gooseneck†) as it goes in and out of the well. This bending and straightening causes an extreme amount of wear and tear. This process is known as cyclic bending and along with the internal pressure may result in a life expectancy of less than 100 cycles. Another downfall is the tendency for the walls to thin, thus increasing the diameter of the tubing as cycles increase. Tests have shown up to 30% increase in the diameter. This plastic type growth is sometimes referred to as ballooning. This effect is worse on the tubing that does not rotate during deployment and the walls thin more on one side that the other. Elongation is another effect that results from the forces of fieldwork, with reports stating up to ten feet of permanent elongation per trip!