Well intervention in highly deviated sour oil wells operating with Electrical Submersible Pump (ESP) completions have always been challenging for well intervention operations due to the restrictions in the wellbore. Workover operations in such harsh environments involve several operational risks and high related costs. Electrical Coiled Tubing (E-CT) equipped with tubing encapsulated mono-conductor cable was used to gather accurate intervention data with real-time logging capabilities. The system used didn't require the temporary installation of a test ESP completion string after pulling the failed ESP pump, saving cost, overall intervention time, optimizing zonal isolation for the water producing intervals, and increasing well recovery in these oil wells.

This case study presents a challenging workover for a mature field where E-CT was used to convey a combination of Pulsed Neutron Logging (PNLT) and Production Logging Tools (PLT) while pumping Nitrogen (N2) to lift the well. This enabled maximizing the reservoir production potential while monitoring the dynamic drawdown being applied to overcome the masking potential for the PNLT due to killing operations during workover. Real-time readings from the PNLT, PLT continuous spinners, gamma-ray, pressure, and temperature sensors accurately identified the well's water contributing intervals and flow profile. This accurate interpretation of the water saturation profile across the reservoir was then used for optimum reservoir management and selective zonal isolation. Dynamic wellbore modeling software was used to design the lifting and logging operations for optimal operational efficiency and to increase oil production and reduce water production.

Deployment of E-CT in such a harsh environment was challenging in terms of operational execution to ensure safe conveyance of the real-time logging tools while performing the conventional lifting of the well. Intervention time was optimized through two runs to evaluate the formation performance and water saturation profile before isolating the water-producing intervals.

Such utilization of E-CT allowed accurate formation evaluation, water saturation profiling, and nitrogen lifting of the well resulting in an optimal intervention. Results showed a 50% reduction in water production and an increasing well potential from the upper intervals. Total workover and intervention costs were reduced dramatically compared to other treatment options for water production problems with potential workover complications and deferred production.

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