Innovative new technologies in coiled tubing (CT) manufacturing will present new opportunities in the industry. The new technology represents a 4th generation CT manufacturing process known as the Continuous Variable Reduction (CVR) process. A brief overview of current manufacturing technology will be presented followed by key elements of the new CVR 4th generation manufacturing technology. Then, the advantages of the CVR technology will be presented along with examples of new products to come from CVR.
Continuous Variable Reduction (CVR) technology has application in the manufacture of variable outside diameter, variable wall thickness, and variable strength all within the same CT string. There is also application in the manufacturing of small diameter, heavy-wall, high-pressure strings. The CVR process will produce CT without internal weld beads.
The significance of the ability to manufacture coiled tubing with variable OD, variable wall thickness, and varying strength levels without the typical ring or "butt" welds now required to join multiple diameters represents a significant advance in coiled tubing manufacturing technology.
Current manufacturing practices and existing technologies for the production of coiled tubing date back nearly three decades. While providing quality products to an industry that has experienced phenomenal growth over that same period, current practices have limitations in production speeds and product design flexibility. A new patent pending technology and manufacturing process called Continuous Variable Reduction (CVR) now offers a means to produce CT with a much higher throughput while simultaneously making possible multiple variations in outside diameter, wall thickness, and strength levels, all without internal weld beads, to meet customer specifications in well intervention applications that require tapered strings (both in outside diameter and wall thickness).
Current coiled tubing manufacturing practices presently join two or more steel strips end-to-end that were previously slit from large master coils. The combined longer strip that meets the total length requirement for the order is then fed through a tube forming mill, longitudinally welded through forge welding (usually called HFIW or high-frequency induction welding), heat treated through induction coils to remove forming stresses and set physical strength properties, and, after cooling, wound onto large metal or wooden spools.
In current manufacturing practices, customer orders which call for tapered wall thicknesses are handled in two different ways. One method requires that master coils be purchased from the steel mill having a gradually tapered thickness from one end to the other. Since several strips must be joined end-to-end typically for a single customer length requirement, this process requires ordering many various tapered master coils with varying thicknesses. A second method of producing tapered wall thicknesses again requires that many different master coils be purchased with only slightly different gauges so that strips can be joined from these close gauges. Tapered outside diameters are not possible with the current manufacturing process and technology without joining two different diameter tubing strings with a perpendicular ring or "butt" weld.