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Case Study

Shell UK’s Brent Charlie Platform with Allseas

Overview

Pins Installed (Subsea + Surface):
112
Cuts Completed:
27
Crumping Ops (Subsea):
12
Average Time Per Operation:
3-7 minutes
Consumable Replacement Rate:
<1%

Overview

Control Cutter played a critical role in the decommissioning of the Brent Charlie platform in the East Shetland Basin, approximately 116 miles northeast of Lerwick. This complex conductor recovery campaign covered 40 wells and marked an important phase in the broader Brent field decommissioning effort, which included Alpha, Bravo, Charlie, and Delta platforms.

Background

The Brent Charlie operation was distinct in that it took place from Allseas’ heavy lift vessel Pioneering Spirit following removal of the platform topsides. Control Cutter served as a key subcontractor for the conductor recovery scope. Two tooling suites were deployed simultaneously — one for surface operations and the other for subsea recovery — making it the company’s most ambitious project to date. Control Cutter also supplied and operated the Dirty Work Pack (DWP), used to operate both Control Cutter’s own equipment and additional tools procured by the client throughout the project.

Challenges

Subsea and Surface Complexity
The dual nature of this operation — surface and subsea — introduced unique engineering and operational challenges:

  • Subsea Adaptation of Surface Systems: Surface tooling like the DecomCutter had to be modified for subsea use. This required reengineering sensors and pressure systems to function without standard signal transmission, all while maintaining full control integrity.
  • Combined Securing and Lifting: The DecomDart Subsea demanded a dual-function pin capable of both inner strings securing and lifting — a design that had to comply with LOLER, BS 7121, and offshore lifting regulations while being ROV-deployable.
  • Third-Party Tool Integration: Control Cutter’s DWP was engineered to interface seamlessly with a wide range of third-party subsea tooling, with control systems and software dynamically adapted as new equipment was introduced.
  • Fully Remote Surface Operations: In response to a directive from the end client, Control Cutter engineered a solution to allow all surface operations to be performed fully remotely from 25–35 meters away, mitigating risk and eliminating manual intervention during high-risk stages.

Innovative Engineering Solutions
Several industry-first technologies and methodologies were developed for this project:

  • OmniPin System: A dual-function pin that served both as a push rod and lifting component. This single-pin solution was certified under offshore lifting regulations and deployable via ROV. It replaced the need for multiple operations, increasing speed and reducing complexity.
  • Custom Lifting Thimbles: Designed for compatibility with the OmniPin, these included secure engagement indicators and could be installed or removed by ROVs or surface personnel, enhancing flexibility and safety.
  • DecomCutter Subsea Crimping and Cutting: Required the redesign of knife elements for deformation of small multistring stubs in the conductor guide frame (CGF). The flattening and cutting operations were remotely controlled using adapted software within the DWP and were supported by a retention system to prevent dropped objects.
  • Custom DWP System: Redesigned to house full control functionality of Control Cutter’s surface tooling, including pressure and signal processing, and extended to operate all client-specified third-party tools subsea.
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