History of the Coil Tubing Injector

The chronology of modern-day steel CT (Coil Tubing) technology development appears to begin in the early 1950s with U.S. Patent 2,567,009, “Equipment for Inserting Small Flexible Tubing into High Pressure Wells,” awarded to George H. Calhoun and Herbert Allen on 4 September 1951. The fundamental concepts developed and claimed by Calhoun and Allen served as the basis for the vertical, counter-rotating chain tractor device, which was upscaled to serve as the design for the first Coil Tubing Injector placed in operation.

This apparatus provided the ability to insert, suspend, and extract strings of elongated cylindrical elements (such as tubing) for well-intervention services with surface pressure present. A modified version of this device was originally developed to enable submarine vessels to deploy a radio communications antenna up to the ocean surface while still submerged. Using the Calhoun and Allen concept, Bowen Tools developed a vertical, counter-rotating chain tractor device called the “A/N Bra-18 Antenna Transfer System,” which was designed to deploy a ⅝-in. outside diameter (OD) polyethylene encapsulated brass antenna from as deep as 600 ft beneath the water level. Fabric-reinforced phenolic “saddle blocks” grooved to match the outside diameter (OD) of the tube were installed as the middle section of the drive chain sets, securing the antenna during operations. The antenna was stored on a carrier reel located beneath the antenna transfer system for ease of deployment and retrieval. The pressure seal was provided by a stripper-type element, which allowed the antenna to penetrate the hull of the vessel. The basic principles of this design concept aided in the development of the prototype Bowen Tools CT injector system.

In 1962, the California Oil Co. and Bowen Tools developed the first working prototype “continuous-string light workover unit” for use in washing out sand bridges in U.S. Gulf of Mexico oil/gas wells, see image below. The original “Unit No. 1” injector was designed as a vertical, counter-rotating, chaindrive system built to run a string of 1.315-in.-OD tubing and operate with surface loads of up to 30,000 lbf. The core diameter of the tubing reel was 9 ft, and was equipped with a rotating swivel mounted on the reel axle to allow continuous pumping down the tubing throughout the workover operation.

Information sourced through PetroWiki

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