Unstable wellbore hindered installation of long casing string
A North Sea operator's well design required 9 5/8-in casing to surface
with metal-to-metal connections throughout. Wellbore instability was a common
occurrence in the field, and the 3,604-m interval included 728 m [2,388 ft] of
open hole that was likely to hinder access. Long, heavy casing strings require
extremely high torque to rotate, making it difficult to ream with casing and
increasing the likelihood of multiple attempts—interspersed with wiper
trips—to run the casing string to depth.
To minimize rig time and optimize costs, the alternative was to install
a shorter, lighter liner across the unstable openhole section and tie it back
to the wellhead with a separate tieback string. However, conventional liner
equipment does not provide the metal-to-metal, gas-tight connection
required.
Proprietary sealing technology enabled use of ream-down liner
Schlumberger proposed a liner system with a setting adapter and a
metal-to-metal, gas-tight liner tieback system that uses Metalmorphology
sealing and anchoring technology. This full-axial-load- bearing, V0 ISO
14310–certified system connects a liner to a tieback string of casing
with a permanent, durable seal.
