Unique Automation System Monitors South Florida Production Operations
Authors: Weaver Edward G. , Hildebrand Steven M. 
Published: December 2007

A unique oilfield automation system has been installed to monitor and control production operations in four remote south Florida fields. A stand-alone local automation system and company-wide design remote terminal units (RTU's) are combined into one system by employing a microprocessor-based control unit. The local system provides operational personnel with alarms, accumulators, analogs, and controls for daily real-time operations. These operational data points, through specialized software, are reformatted and interfaced to pseudo-RTU's within the microprocessor memory. From the pseudo-RTU's, the information is transmitted to the companywide computer production control (CPC) system. The microprocessor-based unit is an efficient and economical method for combining the best features of both automation designs. It also provided the means to implement CPC in an area where conventional large hardware RTU's could not be installed or justified. This paper describes this unique automation system, its equipment, functions, and operation.

Introduction

The south Florida automation project encompasses all Exxon's operations in four isolated oil fields near Fort Myers. As shown in Fig. 1, the fields trend northwest-southeast, with a maximum distance of 50 miles (80 km) between fields. The field office is in Immokalee, and operations range up to 30 miles (48 km) from this location. There are 7 tank batteries and 51 active wells in the four fields. All wells are artificially lifted either by long stroke pumping units or by electric submersible pumps. The two northern fields, Lehigh Park and West Felda, are situated in an urban development area, and the southern field, Bear Island, is within the Big Cypress Swamp Natl. Preserve. This park has common boundaries with the Everglades Natl. Park. The remaining field, Sunniland, is in an area of farms and pastures.

Considerations that led to the automation study were (1) isolated nature of the fields from other operations in Exxon's Pensacola Dist., (2) the extreme distances between wells and fields in south Florida, (3) expanding urban development in the two northern fields, and (4) location of one field in the Big Cypress swamp. Study objectives were to improve production by reducing well downtime through faster response to well problems and to minimize exposure to oil spills in these fields.

The initial assessment of the automation project was based on a typical Exxon CPC system.1 In a normal CPC project, field functions (alarm/status, accumulator, analog, and control) are concentrated into one or two large RTU's. These large RTU's are then linked directly by means of a communication circuit into the division's CPC computer center. It was not possible, however, to concentrate functions in south Florida because of limitations on the use of buried cable in urban areas and in the park. An alternative was to install small radio-controlled RTU's at each site. The division CPC computer's physical limitations and economics negated this approach. A local stand-alone automation system was then evaluated for the area. From this evaluation we developed a system involving small local RTU's and a microprocessor-based central control unit for gathering local functions. Once functions were resident in the central control unit, special programs interfaced the functions into large pseudo-RTU's blocked out in the microprocessor's memory. These pseudo-RTU's could then be economically tied into the division CPC system through software and operated in the same manner as conventional hardware RTU's. Fig. 2 is a schematic of the south Florida automation system.