Fully Integrated and Computer-Controlled Quick Disconnection System for Flexible Risers
Authors: Manson R.J. 
Published: October 2008

ASTRACT

A Floating Production System (FPS) is often a cost effective solution for marginal field production where the cost of a fixed bottom supported platform would make the field uneconomic to produce. The system concept is based on a mobile floating production unit, strategically placed and anchored over the cluster(s) of wells. Flexible import and export flowlines and control umbilicals from the subsea equipment are suspended from the FPS, where processing and control functions are performed. Safe operation of the FPS requires that these umbilicals and flowlines be quickly and safely disconnected from the FPS in the event of an emergency, such as high storm conditions or catastrophic failure on the FPS.

INTRODUCTION

The system described is a compact and lightweight technique for disconnecting flexible risers and control umbilicals. Cameron's electro-hydraulic control system is a third generation system baaed on field proven hardware and techniques. The system design balances simplicity with performance to achieve the reliability expected of a such a critical safety system.

The key features of the system are:An automated primary control system with an operator assisted back-up control system.Sequenced operation of the QCDC to prevent hydrocarbon spillage and pollution.Sequential release of all QCDC'S to ensure that acceptable stress levels are maintained on the FPS.High flow rate hydraulic system for rapid operation.Wide angle release of riser for storm conditions.

QCDC DESIGN BASIS

The QCDC is generally designed in compliance with the following specifications:

FPS Surface Environment:

Design Temperature-10 to 30 Deg. C Humidity5 to 95 % relative, condensing Atmosphere salt laden, corrosive.

Control Room Environment

Design Temperature0 to 40 Deg. C. Humidity20 to 80 % non-condensing Atmosphere condition mildly salt laden

Operating Environment

Medium - Wet Oil and Gas with H2S & C02 also water Injection Typical Pressure - up to 5000 psi Temperature - 4 deg to 120 deg C Typical loads 4" 8" Bending 7,000Kgm 10,000 Kgm Shear 3 tonne 4 tonne Axial 6 tonne 9 tonne

APPLICABLE TECHNICAL SPECIFICATIONS

UK Government:

Petroleum and Submarine Pipelines Act 1975. Prevention of Oil Pollution Act 1971. SI 289, 1974, Offshore Installations. SI 1019, 1976, Offshore Installations - (Operational Safety, Health and Welfare) Regulations. SI 419, Offshore Installations (Application of Statutory Instruments) Regulations.

British Standards

BS 5760 - Reliability of Systems, Equipment and Components. BS 5345 - Selection, Installation and Maintenance of Electrical Apparatus for use in Potentially Explosive Atmospheres. BS 55 - Atmospheres. BS 54 - Protection Provided by Enclosures. BS 5500- British Pressure Vessel Code. BS 5501- Electrical Apparatus for Potentially Explosive Atmospheres.

International Standards

API 6D - Pipeline Valves. API 16A - Drill Through Equipment. API 607 - Fire Test for Soft Seated Valves. API RP14C - Regulations for Production and Storage. API RP14D - Wellhead Surface Safety Valves & Underwater valves for Offshore Services. API RP14E - Design and Installation of Offshore Production Platform Piping System API RP14F - Design and Installation of Electrical Systems for Offshore Production Platforms.