Abstract
A new high strength coiled tubing grade has been developed to address the demands for improved axial strength, better fatigue performance and the ability to function at higher operating pressures. Coiled tubing service companies and operators defined several areas where existing coiled tubing grades are not considered capable of performing, including carrying heavier payloads to the well perforation zone and working in today's increasingly longer horizontal sections. Designing a coiled tubing product that meets these requirements presented unique challenges. The project goal was to develop reliable high strength coiled tubing that provides 130,000 psi minimum yield strength and predictable fatigue life. Coiled tubing strength comes from a balance of strength from the initial hot rolled strip and modifications while forming into tubing. However, some coiled tubing manufacturing operations, including welding, can influence those strength characteristics. The process controls during manufacturing, including bias welds and any tube to tube welds needed to assemble long strings; all determine the final properties of the tubing. The high strength tubing has been successfully made using existing manufacturing methods. The initial testing indicates the tubing has high strength with good ductility. Fatigue testing shows superior fatigue performance to existing grades of tubing in both cycles to failure and diametrical growth. This paper will cover the development program inclusive of strip manufacturing, tube forming, welding and other processes including the quality control necessary for assuring consistent properties. Initial application trails to verify operating characteristics will also be reviewed in the paper.
