Abstract Despite higher cost implications, it is not uncommon that fishing work in large size completions ends up conducted by a workover rig instead of traditional rigless intervention methods. Top of fish (TOF) accessibility, alignment between the fishing tool and the fish, and restricted pulling capacity are some of the typical challenges encountered around this work. This paper describes a tailored intervention workflow for coiled tubing (CT) fishing operation in large size completion that enabled averting a costly workover rig operation. The objective of the intervention was the fishing and retrieval of a wellbore isolation plug stuck inside a 9 5/8-in. × 7-in. completion. Initial fishing attempts with slickline were unsuccessful as TOF was not accessible due to the presence of debris. Extensive CT software modeling was carried out for guided selection of the CT pipe, fishing tools, and modeling of cleanout work. TOF accessibility was restored through wellbore cleanout with high-pressure rotary jetting tool. Then, the centralized fishing assembly equipped with flow-release fishing tool, allowed optimal tool manipulation and effective latching of the fish neck. Upon applying the preset pulling force, the isolation plug was unset and retrieved to the surface. The rigless fishing intervention was successfully conducted in two CT runs. The initial run consisted of a wellbore cleanout to restore accessibility to the fish. In line with CT hydraulics modeling, cleanout operation was carried out with nitrified fluids to deliver the required annular velocity for efficient solids transportation inside the 9 5/8-in. casing. Likewise, high-pressure rotary jetting tool was used for 360-degree wellbore coverage and effective scale removal. Accessibility to the TOF was restored at the end of this stage, and close to 150 kg of scale were recovered at surface. The fishing operation, executed in the second run, achieved first-attempt success with a 34,000-lbs overpull, retrieving the plug without damage. Centralization requirements across the transition from 9 5/8-in. to 7-in. casing were resolved through dynamic adjustments in the fishing assembly. Extensive pre-job planning, including detailed simulations and risk assessments, played a crucial role in this success. The tailored intervention eliminated the need for workover rig deployment, restored the well to production in less than six days, and reduced operational costs. These results underscore the operational robustness and flexibility of CT in complex fishing scenarios. As the industry strives for cost-effective and sustainable interventions, the case study presented in this paper provides an example of how a custom-fit CT intervention workflow for complex fishing operation saved a costly workover rig intervention, while reducing near 70% CO2 emissions.
Naveed et al. (Tue,) studied this question.