Monitoring and Control System for Offshore Oil Processing
Authors: Newcomb Paul F. , Perkins James F. , Lane Larry F. 
Published: October 2008

The system performs three very important functions in the operation of oil field equipment. These functions are surveillance data gathering and control.

The control system is designed such that it can operate closed loop exclusive of personnel whereby required emergency action to certain alarm conditions such as high or low liquid levels in certain stages, or fire detection and foaming action, can be acted upon with no personnel being available in the control room. The control system, by monitoring various possible alarm sensors, is equipped to give three different tones of audible alarms. One tone, alarm "C" sounds in the event some monor alarm condition is present. Another tone, alarm "B", sounds in the event of a major, but not drastic alarm. Another tone, alarm "A", sounds in the event of a very major and drastic alarm such as fire action. The control system is designed such that all routing of incoming and outgoing products can be controlled from one main control room by the operator determining which valves are to be opened or closed by looking at a flow diagram and actuating the correct valving for routing to appropriate separators, etc. The status of all equipment such as pumps, generators, flow computers, batteries, foghorns, valves, flame detectors, and gas detector are monitored, recorded and acted upon from one main control console. All commands, functions and alarms are designed in such a way that the system can be readily tied into a telemetry control station. The system also has the capability to perform for a period of up to eight hours on standby battery and also to furnish low-current 115 vac power to various critical components in the event of a complete power failure.

Also in our paper we will discuss the highly important manufacturing and assembly techniques involved in building a system that will perform under the extremely corrosive atmosphere of salt water or off-shore application.

TEXT

The system to be discussed in this paper is designed to control and monitor a five platform oil, gas production complex located approximately 20 miles offshore from the coast of Louisiana in the Gulf of Mexico. Three basic functions are accomplished by the system, viz.:SurveillanceData gatheringControl

Serious alarm conditions cause automatic control action, exclusive of personnel, on a closed-loop basis. All control functions and alarm monitors throughout the process complex have fail-safe operation. Failure of any control or alarm sense device will cause-an alarm.

It is important to note that the control loop for emergency action does not include the telemetry link to the supervising control computer. See Figure 1. Control Block Diagram.

This system7 in addition to replacing the conventional analog controllers, supplies a natural extension to a remote supervising control computer, located on the mainland. The status and control of all manifold values, alarm sensors, gas flow rates, etc are tied via telemetry to the mainland computer. This allows for a quite sophisticated level of control, utilizing the inherent advantages of the digital computer in optimizing the production throughput of an entire district, by total overall supervisory control.