Abstract
Tapered outside diameter coiled-tubing (TODCT) systems have distinct advantages in ultra-deep wells (30,000-ft range) Introduced in 2004, the TODCT system includes: (1) a modified injector that can handle more than one diameter of tubing and maintain a constant grip on the tubing throughout the length of the TODCT string, (2) an ODT "transition tube" that allows sections of tubing with different ODs to be joined together, (3) well pressure control equipment (i.e., blowout preventer and stripper) with the capability to grip and seal more than one diameter of tubing and also grip and seal the transition tube, and (4) an operator control house that allows remote control of the stripper elements and injector gripper elements to open or close to different diameters of tubing while still maintaining control of well pressures inside the wellbore and grip on the tubing.
This paper presents a review of the yard testing completed on the TODCT system equipment and then describes a subsequent field trial conducted onshore in south Texas. The end result is a tested and qualified TODCT system capable of safely running tubing strings into ultra-deep wells.
