A hybrid geometry-based method for roll forming of coiled tubing and experimental verification

Coiled tubing (CT) is an efficient method used in petroleum well drilling, involving winding a High Strength Low Alloy (HSLA), flexible metal tube onto a reel, creating thousands of meters in length. The tube is unwound, straightened, and inserted into the well, repeating until the tubing requires removal due to fatigue. Precise manufacturing of these tubes is crucial for their mechanical resistance, performance, and lifespan. This study introduces a hybrid analytical-numerical geometric approach, referred to as the Geometry-Based Method, to predict spring-back effects during the roll-forming process of thin-walled tubes. Specifically, it simulates the roll-forming of a 1.5 inches (38.2 mm) QT-70 tube using a reverse bending flower pattern. Following this, a 12-m tube was manufactured using the same technique. Results show strong agreement between theoretical predictions and experimental findings, with the simulation showing no errors in average thickness. The experimental error was just 0.32%, but the simulated tube had an ovality of 2.68%, compared to 1.80% for the manufactured tube. In conclusion, the Geometry-Based Method uses three-dimensional geometry to analyze the properties of forming materials and rollers, helping manufacturers reduce costs while maintaining accuracy.