This paper provides a case study review of the deployment of new reamer technology to the Troll field and the resultant performance improvement.

For the past several years expandable, concentric reamers have been used to drill the 12 1/4-in. x 13 1/2-in. landing section of multilateral production wells on the Troll field in the North Sea. Drilling with a pilot bit and reamer through this interval, which includes interbedded sands and hard calcites, is extremely challenging; the consequences are potentially destructive drilling vibrations, sub-optimal performance and significant drilling inefficiencies.

The operator invited the service company to run its recently developed expandable reamer and expandable stabilizer to determine the benefits of this new technology. The thorough design of the reamer ensures that it remains closed until triggered, opens on command, reams an in-gauge hole, then closes and comes out of the hole properly. The reamer benefits from a reduced number of seals and moving parts and an optimised cutter layout. The innovative expandable stabilizer was developed to provide full, rather than partial, stabilization above the activated reamer in the reamed hole. Typically when a stabilizer is placed above an expandable reamer it is constrained by pass-through size and therefore less effective. The expandable reamer and stabilizer combination ensures that the bottomhole assembly (BHA) is fully stabilized, with an optimal size stabilizer.

This is the first worldwide landing / horizontal application drilled with these tools and the first run in the Eastern Hemisphere. The only previous experience with the technology was on test runs at the service company's test facility in Oklahoma and drilling in the Gulf of Mexico (GoM.) The Troll 12 1/4-in. x 13 1/2-in. landing section was drilled to section total depth (TD) in one run, with both the expandable reamer and expandable stabilizer working as planned and with minimal vibrations and tool wear. The 9 5/8-in. x 10 3/4-in. liner was subsequently run smoothly to TD. The success of this run highlights the benefit of combining an expandable stabilizer with a concentric expandable reamer. The lower vibrations and improved drilling efficiency make this a preferred configuration for subsequent applications.

The paper describes the engineering design and testing practices used, the modelling capability and the performance results of the first run and three other runs that comprise the testing programme on Troll.

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