Automatic Control And Operation Of An Offshore Oilfield And Production System
Authors: Williams P.G. , Coombes E.J. 
Published: December 2007

Large offshore complexs providing water injection and production facilities have been installed and successfully operated offshore Abu Dhabi for two years. These platforms use modern control methods using pneumatic safety and control systems together with advanced telemetry and computer monitoring packages.

Introduction

It had become necessary to inject water into the oil reservoirs to maintain production rates. The field was offshore, approximately 20 miles from the production and storex complex based on an island. The island itself being over 100 miles from the mainland. It was apparent from the water treatment and injection requirements that a massive amount of power would be required. This in conjunction with the possibility of offshore crude oil and gas separation and gas dehydration facilities led to the design and installation of a large manned platform - a super complex.

As the sea was relatively shallow, around 20 metres, it was decided to build each individual process unit on a separate platform and process unit on a separate platform and interconnect them by means of bridged walkways. This gave the advantages of segregation of potentially hazardous plant, clear definition of safe areas and ease of access for maintenance.

In the interest of reliability, simplicity of operation and robustness it was decided to use local pneumatic control instrumentation with remote monitoring, shutdown and limited supervisory control from the central control room via a computer based telemetry system.

The use of this central computer facility led to the incorporation of the field wellhead towers, flow computation production logging facilities etc. into one integrated system. Information from an other field telemetry system was also made available via microprocessor interfaces and microwave telecommunication links.

These developments led to an enormous increase in efficiency and safety of operation of the field. A similar super complex was installed in an adjacent field and from the experience gained with the first two a third super complex is being designed. Experience has shown that the form of hierarchal automatic control philosophy adopted breeds more and more ideas as to how to improve the system and its operation.

THE SYSTEM

(i) Plant and Instrumentation

The super complex is divided into six platforms joined by bridge type walkways these areAccommodation platform including Central Control Room.Power Generation Platform.Water Injection Platform.Riser Platform.Collector - Separator Platform.Gas Treatment Platform and its associated Gas wellhead platform. andFree standing wellhead towers.

The platforms individually hold the following system :Accommodation PlatformThis platform contains the accommodation and central control room for the super complex. The equipment consists of air conditioning, ATK system for helicopter fueling, helideck, emergency diesel generator set, firefighting pumps, salt and fresh-water pumps and sea water distillation plant, battery room, radio room and radio tower, workshops, recreation areas, sewage equipment, sick bay, kitchens, messing, bed rooms, etc. The whole is protected by a fire and smoke detection system protected by a fire and smoke detection system which can discharge inert gas or a water sprinkler system and is monitored on the central control room panel.