INTRODUCTION

The Shtokman field development in the Barents Sea will be another milestone in the industry, with a challenging step-out distance and demanding environmental conditions. This paper will discuss the all-electric controls solution using the CameronDC system approach and its advantages over conventional systems. Some illustrations and conclusions are taken from technical evaluation studies recently conducted for several operators.

Design Goals for CameronDC Controls System

CameronDC technology is particularly applicable for long offset fields, though not specifically developed for those applications. The following principles were set early in the development process:

  • Increased reliability: the removal of hydraulic components from the control system; a key factor in increased component reliability and system availability improvement.

  • Elimination of control fluid: no hydraulic fluids to store, handle, transport, clean/flush, replenish or disposal resulting in cost savings and significant environmental benefits

  • Enhanced functionality: improved equipment response times and system diagnostic capabilities

  • A power transmission system designed to economically overcome distance limitations of current electro-hydraulic systems

Challenges

Requirements for extreme offset field developments such as Shtokman offer design challenges that have not been addressed previously. The subsea installation is up to 640 km away from the topside system. This distance provides a unique challenge for conventional electro-hydraulic systems, not only from operational and economical perspectives but also from a logistical perspective. The application of the all-electric CameronDC system completely eliminates the need for control hydraulics. This results in major advantages in production umbilical configurations as a much simpler and significantly less expensive power umbilical containing coaxial cables with fibre optic capability is used.

The field lies in a region of permanent ice during certain times of the year, making it impossible to access for intervention activities. Significant improvements in system reliability and production availability over are required. Numerous studies demonstrate that all-electric CameronDC technology provides the necessary improvements that will reduce the need for intervention and the associated operational cost of the production system.

Further advantages of all-electric controls and actuation involve addressing important issues in health, safety and environment (HSE). Total elimination of hydraulic fluid and the equipment necessary to store, pump, pressurise, filter and dispose of it is a significant benefit. Associated health and safety issues including contact with, or slipping on, spills on the deck due to handling and leaks are greatly reduced. Also, safety is improved by elimination of high-pressure accumulator bottles and pressurised hoses and lines. In addition, environmental problems are obvious when leaking and venting hydraulic fluid into the sea. These are alleviated with the use of all-electric controls technology.

The Approach for Shtokman

The system concept can be broken into several areas such as communication architecture, power system design and subsea control system design (see Figure 1). The subsea system configuration for Shtokman consists of three templates situated in distances of approximately 12 km. Each template provides the space for up to eight Xmas trees. A ?dual redundant? control system was selected due to the specified high production availability targets.

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