Re-Perforating Formerly Inaccessible Well Areas Beneath Completion Collapse and Axially Displaced Tubulars
Authors: Duncan Troup , Roy Kristiansen , Maxime Maouche 
Published: September 2019

Abstract
In several producing fields throughout the Norwegian continental shelf, operators are facing aging wells with heavily deformed completions that are producing below their potential. In order to find a technical solution to improve production that can be operated through completion deformations, Archer, Archer has pursued a full technical study of existing collapse geometry, axial pipe displacement and reproduced them in full scale 3D models in order to test a newly engineered slim and highly flexible perforating system designed to be conveyed by carbon composite rod with embedded electrical cable.
In March 2018, work began in parallel on two linked projects. We needed first to understand the different profiles and geometries of an inaccessible deformed tubular, in order to reproduce and model the axial displacement on scale. In parallel with the deformation modelling, we needed to engineer with our perforating system manufacturer an interchangeable and flexible perforating system capable of passing through the 3D model deformations.
A complete study of downhole recorded well data from deformed areas was performed to catalogue the different possible shapes and internal diameter reduction of tubing and liner under axial compression. A 3D modelled transparent plastic tubular system has been engineered in order to reproduce the exact downhole dimensions and conditions of known deformed areas. The modelled deformations needed to be robust and long enough to support real downhole tools and fully transparent so we could understand the different toolstring’s behaviorsbehaviours depending on the Bottom Hole Assembly (BHA) set up and shape of the deformation. The deformation testing system has been created as a light weight interchangeable tubular system designed to interlock quickly and easily in various combinations.
In the meantime in the parallel twin project, the initial task was to review the current product portfolio of slim through tubing equipment. The completion with heavy wall liners, intended to minimize the deformation caused by reservoir formation movements, challenged the charges selection that could be fitted into slim perforation systems. Due to the minimum hole size requirement, the gun system was also designed to self-orient to the low side of the casing. The drafting team analyzedanalysed the internal gun system and added a weighted row to assist with gun orientation. The final system to be tested in the modelled deformation is composed of interchangeable swivels, knuckle joints, rollers, and single or multiple shot slim and short guns incorporated with addressable switches.
Over 30 different well deformation shapes have been recreated in order to test and select the best performing flexible perforating system combination, leading to more than 200 documented results. The flexibility and reduced Outer Diameter (OD) of both downhole system and composite carbon rod allows to pass successfully through several heavily deformed tubulars, when every other conventional rigid system have has failed.