Challenge

An Operator drilling a well in the Central North Sea encountered difficulties in the 12 ½” section of the main wellbore. Weak layers in the overburden at the top of the section combined with a gas bearing layer close to section TD resulted in a complex well control situation. As a consequence, the well was plugged and abandoned and then prepared for a sidetrack below the existing 14” casing shoe. A liner system was required to isolate the weak layers in the overburden and provide a sufficient mud weight window to drill high pressure and gas bearing zones – all without losing too much ID to allow subsequent running of the next planned casing string.

Solution and Results

Due to the high pressure, high temperature nature of the well the 11-3/4 in 74.4 lb/ft. 400 deg F rated ESET expandable liner was utilized. Careful planning, testing and collaboration with the Operator resulted in the High Performance (HP) expandable liner effectively isolating the required interval and allowing the subsequent 9-7/8 incasing to pass through. A record length for this expandable configuration of 2,766 ft. was installed in the sidetrack with 656 ft. of the expandable liner fitted with bonded centralizers to assist with cement placement. The liner was successfully rotated at TD, a first time rotation of this particular liner specification. The system was fully expanded, pressure tested and the shoe drilled out with no issues allowing the Operator to continue with their planned operations.

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