Cleaning operations are often required as a preparatory Intervention task. In collaboration with a North Sea operator, Welltec® would need to find a combined clean-out and mechanical manipulation solution to open a Formation Isolation Valve (FIV) – the valve had failed due to buildup of debris.

Prior to Welltec’s involvement, the client had attempted to manipulate the valve via several pressure cycles from surface, but to no avail, with a third party failing to succeed using wireline mechanical tools.

It was estimated that 18 ft of fill/debris was positioned above the valve, with the minimum inner diameter through the interval at a narrow 2.94”. The 218 Well Cleaner® Power Suction Tool (PST) would have the capability to pass through the interval and perform a significant clean out operation. Only then would it be possible to fully manipulate the FIV.

The debris above the FIV was believed to be hard-packed Sodium chloride mud. The Well Miller® Reverse Circulating Bit (RCB) was deployed first, combining a rotary bit with a suction system to simultaneously mill and extract hard debris.

The initial plan was to clean down just past the shifting profile, but with a good rate of penetration it was decided to continue down to the ball itself. Over two runs with the RCB, the bailer sections were filled to 100% capacity with the majority of the material being mud. Some metallic debris of significant size was also recovered. Once the ball had been reached, the Well Stroker® and Well Key® were run in hole to manipulate the valve.

Despite a small drop in pressure (suggesting that the valve had moved) the shifting profile slipped under 18,000 lbs. of force, indicating there was still debris inside the valve. Given the prior recovery of metallic debris, it was decided to run the Well Cleaner® Power Suction Tool (PST) with a large nozzle to facilitate the collection of any remaining large material. Five runs were performed with the PST, again achieving 100% recovery, translating to 24 liters of fill and 19 ft of depth.

With the ball tagged, it was decided to rig up with the shifting bottom hole assembly again. The shifting profile was latched first time and the valve was successfully opened via 22,500 lbs. of force.

First and foremost, the main goal of the operation was achieved with multiple clean-out runs gaining access to the ball valve, and the cleaning of the shifting profile enabling a successful valve opening – a task the operator had previously been unable to complete by wireline.

A total of 10 runs were carried out over eight days, with the client hailing a “Great performance by personnel and equipment” throughout the job, and a high level of service quality. Bailers were filled to 100% capacity on every run involving recovery, resulting in an incredibly efficient operation.

This case is also an excellent display of the combinability of Welltec’s tools, with every aspect of the operation catered for: conveyance of tools, milling, cleaning, extraction and collection.