Intricate Subsurface Safety Valve Lockout Executed by Innovative Electric Line Dual Stroker Operation, Securing Well Access and Restoring Production
Authors: Murchie Stuart William , Hansen Rune , Andersen Kristian , Tinnen Bård Martin , Sætrevik Martin Severin , Grønnerød Anders , Wang Lingdi , Russe Kerstin , Hu Shilei 
Published: March 2022

A well with a malfunctioning tubing retrievable sub surface safety valve (TRSSSV) was shut in until a lock-out operation could be undertaken, one which would secure the valve in a fully open position, enabling subsequent intervention programs to be carried out and the well put safely back on production. The TRSSSV design utilized a flapper valve with a power spring mechanism which forces the valve to a normally closed position. Control to the flapper had been lost as the hydraulic communication had been cut off. Repeated attempts to lock open the valve using the conventional lock out tool were unsuccessful, with its flapper returning to the closed position over time.

The innovative solution presented in this paper was to engineer a simultaneously operated dual stroker electric line toolstring assembly, one leveraging several technology elements and executing several steps in a single run operation: (1) to position the work string correctly prior to engaging with the TRSSSV flow tube, (2) to operate the upper stroker to provide the axial force and stroke distance required to push the flow tube down to fully open the TRSSSV and hold it there until "locked", and (3) to simultaneously operate the lower stroker with expander adapter and dimple tool, to deform the valve flow tube and integral lock out sleeve when in a precise and predetermined position and in doing so permanently locking the valve in the open position. Carrying this out as a single trip operation would ensure the dimpling occurred only with the flow tube in the exact required "valve open" position.

Individual communication & control and power sharing of both strokers was maintained throughout the operation using two surface computers in a master/slave configuration enabling a simultaneous coordinated operation. A NOGO sleeve was incorporated into the toolstring which aided precise depth correlation and space-out. Unhindered access for the subsequent intervention runs was ensured by using an eight arm multi-dimple device to prevent any ovalization of the flow tube during deformation. Force and distance limits for each stroker were set accordingly to ensure precise positioning during all phases of the operation such that no inadvertent forces would be applied to the TRSSSV.

The job was executed following thorough pre-job design and verification tests. The pre-determined stroke force and distance requirements of the upper stroker to shift the TRSSSV into the open position, and those required from the lower stroker to expand the dimple tool and deform the flow tube to the pre-requisite extent, were applied and measured in real time.

Some initial electric line runs were also carried out as part of the overall operation, namely a broach and a brush for cleaning possible scale accumulation. Following the successful lockout, the required diagnostic logging was completed, a straddle deployed to hold a wireline retrievable subsurface safety valve, and the well brought back into production.