Enabling Extended Reach Coiled Tubing Interventions in Long Horizontal Wells Using Offshore Butt-Weld and Downhole Tractor Technology

Abstract

This coiled tubing (CT) extended reach (ER) trial was developed to address platform-based intervention challenges in high-friction open hole (OH) horizontal wells with high Measured Depth (MD) / True Vertical Depth (TVD) ratios, limited deck space, and restricted crane capacity. The primary objective was to demonstrate the feasibility of deploying a custom-designed CT string that was split for transport, butt-welded on the platform, and run to total depth (TD). The secondary objective was to establish a viable method for matrix stimulation after reaching TD using an ER hydraulic tractor with extreme expansion grippers and a turntable system for multi-well access. A pipe design optimizer was used to develop a 2-in. hourglass CT string that balanced reach capability with offshore handling limitations. Welding qualification, bend-cycle testing, corrosion testing, and acid compatibility testing were completed to validate the selected pipe design, wall thickness, and stimulation fluid system. Prior to offshore execution, a full mock-up test was performed to practice pipe-end alignment, welding in an enclosure, weld inspection, spooling, pressure testing, and tower rig-up activities. The trial was successfully executed across two wells, including pipe alignment, butt welding, spooling, pressure testing, and ball drift verification. In Well 1, CT lockup occurred earlier than expected, indicating elevated wellbore friction. The tractor was engaged from 8,012 ft MD and enabled access to 16,615 ft MD, achieving more than 8,600 ft of tractor-assisted travel. A custom all drop acid jetting sub was activated at depth, and vessel-based matrix stimulation was completed without incident. Preliminary post-operation testing indicated a 100% increase in injection rate, confirming effective stimulation placement. A second run was also completed on well 2, which largely confirmed results from well 1 confirming the lessons learned from the trial. This paper documents an integrated workflow for ER offshore OH intervention with practical lessons in CT welding, ER tractor deployment, bottomhole assembly (BHA) design, pipe fatigue validation, and offshore execution of ER OH matrix stimulation.