Annular Packer Seal Remediation through the SS in a Dual Completion Using Coiled Tubing: Onshore Niger Delta

Abstract

A dual string well in the Northern Niger Delta was diagnosed with a well integrity problem resulting from mechanical setting failure of the long string (LS) packer during initial completion. The well was designed to produce the deeper condensate reservoir through the LS and shallower black oil through the short string (SS). The packer failure created wellbore communication across the two strings, which resulted in the shutting in of the well because of a sudden increase in water cut. The communication was evident in the condensate production from both strings, suggesting production loss from the deeper condensate reservoir to the shallower black oil reservoir. A cost effective solution without recompletion was necessary to isolate the leak across the packer and eliminate the cross string communication. The initial proposal was to perform a rigless through-tubing operation that would involve setting plugs in the LS and perforating the LS to enable setting of the cement plug on the failed packer. The downside to this approach is difficulty milling the cement and plugs in the tubing after the operation, as well as the complexity of the entire operation. This paper presents a novel solution to the problem by deploying coiled tubing (CT) with optimized cement slurry through the SS. Six CT runs were made, exiting the SS 1,365 ft in each run and thereby eliminating the cost of plugs and perforation in the LS. The pump and pull method was used to spot the cement plug. The packer leak was isolated, and black oil production was established through the SS. Postoperation production proved the design a success. The procedure was implemented resulting in more than a 60% increase in production from both strings, and water cut was reduced to less than 1%. A cost reduction of more than 90% was realized compared to a workover option.