Extended Coiled Tubing Straddle for Integrity Restoration: Three Deployment Cases from the Norwegian Continental Shelf

Abstract

An innovative remediation technique has been introduced to the Norwegian continental shelf (NCS) leveraging extended-length coiled tubing (CT) straddle systems to isolate corrosion-induced tubing failures. This method restores tubing integrity with minimal intervention effort. Therefore, offering a cost-effective alternative for restoring integrity and production without the need of pulling the upper completion.

A comprehensive suite of downhole tools and surface monitoring systems enabled the deployment of extended coiled tubing straddles exceeding 1,000 m in a single run. The CT string functioned as the straddle body, integrated with a packer and anchoring system. A glass plug was utilized to achieve zonal isolation during installation. The straddle assembly incorporated a gas lift system, a 2-7/8-in seamless CT pipe and an upper packer and anchor configuration. Final reservoir access was restored by hydraulically rupturing the glass plug, completing the installation without requiring conventional workover operations.

The CT straddle system was successfully deployed in three wells on a normally unmanned platform in the NCS. Each well was suffering from tubing integrity failures of up to 1700m corroded tubing, that had halted production. The installations demonstrated that straddle length is governed by well architecture rather than conventional bottomhole assembly deployment constraints. A three-run sequence was executed: (1) installation of the glass plug, packer, and lower anchor; (2) deployment of the stinger, gas lift valve, straddle section, and upper anchor/hanger; and (3) final placement of the stinger and packer to achieve sealing of upper packer and anchor. Well 1 covered 1019 m, well 2 covered 1124 m and well 3 covered 1726.5 m of total straddle length. The straddle system incorporated a gas lift design that restored the functionality of the original completion and allowed future optimization by replacing valves integrated into the lower packer assembly. Reservoir access was restored by hydraulically rupturing the glass plug. This approach proved to be the most cost-effective and operationally efficient method for restoring well integrity and resuming production.

This approach introduces a novel method for restoring integrity and production by integrating a CT pipe as the straddle conduit, anchored with upper and lower packers. Enhanced with a gas lift mandrel, this method enables zonal isolation and lift optimization in a single intervention. It is suited for brownfield applications where tubing corrosion or mechanical wear is prevalent and can be scaled to an alternative option for water shut off, with minimal operational disruption.