Copyright © 1992, ISA Services, Inc.

Reprinted with permission from, Industrial Computing, Volume 11, Number 8, pg. 42


Imperial Oil integrates Supervisory Control and Data Acquisition (SCADA) information processing networks between fields and headquarters: a case study of oil industry computer users.

By Charles Sykes

As a major oil producer, Imperial Oil Resources Ltd., a subsidiary of Exxon Corp. in Calgary, Canada, deals with a significant degree of risk and speculation in its unending search for new oil and gas reserves. Explorations are subject to a variety of constraints - including significant environmental regulations, strict workplace safety procedures, and global market fluctuations. Many of Imperial's fields are located in inaccessible regions marked by adverse weather conditions. These factors drive up operating costs substantially. One proven way for Imperial to make the most of its capital investments is by integrating computer systems and software in its operations.

Imperial's regional headquarters in Calgary, Alberta, oversees operations in over 20 fields in Western Canada, where natural gas and light crude oil are produced and shipped by pipeline to refineries and joint venture partners. The financial and engineering staffs at head quarters began a project in 1991 designed to capture and manipulate the massive streams of production data at seven major fields.

One portion of this project focuses on capturing the information generated by the SCADA systems and the distributed control systems (DCS) at each field, and correlating that information with local workstation-based, and corporate mainframe-based applications in the Calgary headquarters. This sub-project is known as Automated Data Capture (ADC), and its field systems are being installed at those seven fields by tesserNet Systems Ltd., a systems integrator in Calgary. ADC at the field level encompasses two related projects:

  1. Field Data and Control (FDC), a SCADA replacement project that evolved from and earlier field production control system for modelling an oil field's alarming and automated well-testing sequences.
  2. Data Plug, which seeks to plug the information gap in the network interface between the DCS and the Oracle database.
In the summer of 1992, Project Data-Plug was under way at the Quirk Creek Gas Field. Field Data and Control was installed and operational at the Judy Creek Oil Field in September 1991, and completed this fall at the Norman Wells Oil Field. Field control was performed on Data General System 20 platforms in the 1980s at these and three other fields. But Imperial needed richer connectivity into a LAN infrastructure to monitor trending and field events, and so began to replace the DG systems with RTAP/Plus, a workstation-based application enabler from Hewlett-Packard.

In the Fields - The goals of the ADC project are apparent from an overview of operations at Imperial's oil and gas fields.

The Judy Creek Oil Field, near Swan Hills, Alberta, covers almost 100 square miles in which about 300 wells pump light crude, or "sweet oil", from underground reservoirs.

To manage this information-intensive environment, RTAP/Plus runs on an HP Apollo 720 workstation, which doubles as a file server for two HP 700 X-terminals, connected via a local area network. RTAP/Plus provides a real-time display of operating conditions for alarming or control. Selective data capture to an Oracle SQL database is available - from which Imperial's engineering staff develops data models of the entire field or simulates process scenarios.

Production data originates from each group of 1-16 wells as Judy Creek, which feed into one of 32 "satellite" facilities. Remote Terminal Units (RTUs) at these satellites measure the oil, gas, and water flow of each well. Then production is shipped to the oil battery.

Most wellheads also have an RTU to monitor temperatures, pressures, and flows. These supply SCADA information to RTAP/Plus by radio transmissions. RTAP/Plus also reads from a Bailey 90 DCS through a hardwired serial connection, and separately uploads data through a LAN bridge to a PC network. The network runs Novell NetWare and uses an Oracle database on a SUN platform as an area "datastore". Overall, Judy Creek's SCADA environment includes about 220 RTUs. Production data is transmitted to Calgary by land lines over a wide-area network at 56 Kbps.

The FDC system manages all well-head control and the testing, alarming, and control of the satellite facilities. About 80 percent of the wells have a dedicated HP RTU for wellhead management, which runs a specialized algorithm developed by Imperial. The satellites use RTUs from Teledyne or TRW. Through these linkages, Imperial reacts more quickly to the dynamics of the field.

Norman Wells - At the Norman Wells Field, a slightly different FDC configuration was installed (see illustration). Sixteen Modicon PLCs acting as RTUs send data via radio transmissions to RTAP/Plus on an HP Apollo 433s, connected via a local area network to a backup HP Apollo 433s, and to three HP 700 X-terminals. These connect via serial link to a Fisher Provox DCS through a PC-based system. As at Judy Creek, the data are transferred through a LAN bridge to a PC network running Novell NetWare and an Oracle datastore on a SUN platform.

FDC Configuration Image (79679 bytes)

Advanced Operations - Operations at Judy Creek include miscible flood (the mixing of natural gas with purchased ethane, for pumping into the underground strata to improve oil flow to the wellbore). This requires very precise blending and precision wellhead monitoring because extremely high pressures are used to force the gas underground. The miscible flow and blending data, and related data for accounting purposes, are transmitted at 56 Kbps via a wide area network from the Oracle datastore to Calgary. There is a staff of 120 at Judy Creek, and 1500 at Calgary. About 550 of the Calgary staff are engineers.

Streamlining the Data Flow - Field production data is used by the Calgary engineers to investigate specific wells or well field areas that appear promising. Other information is used by the accounting staff to monitor field production and related accounting functions more precisely. Imperial especially wants data on the production volumes of the oil it sells to pipeline carriers to be more quickly accessible. The pipeline companies receive oil and gas from many different suppliers.

Contractually, the onus is on the suppliers to produce to quotas set by the pipeline companies using the current monthly accounting methods. Imperial many not learn of production overages or shortfalls until the end of the month, possibly incurring penalties from the pipeline companies. The ADC project, therefore, will assist in accounting on a daily basis. The Canadian government, at the provincial and federal levels, needs that information as well, for ecological purposes. It's concerned that too-rapid production may damage reservoirs, leaving oil unrecoverable in the ground.

Managing Information Technology - Imperial's Calgary office tower has many major application packages on its IBM mainframe, including Profs E-mail from IBM, Db2 from Ashton-Tate, Oracle, and a suite of specialized oil field accounting tools, each with its own database, and each heavily customized. Much time is spent writing patches and data extracts among packages. All users are connected via PC LAN. An important goal here is to streamline the information technology by reducing the number of disparate software systems. This is the goal of a corporate-wide database and LAN/WAN configurations, and more reliance on commercial software such as Octagon for field use and Triangle for revenue and accounting use. RTAP/Plus on an HP Apollo 425T in Calgary will support the field systems.

Preserving a Real-time Response - In the field production environment, an important issue is controlling the number of random queries that potentially can bog down the real-time plant control system. tesserNet Systems is writing the programs and configuring computer and SCADA systems to manage this information flow in an orderly, sequenced process. In the SQL client/server model, the server - not the client - gets bogged down with uncontrolled, nonessential queries. Some control companies plan to offer SQL query capabilities in their databases, according to McClure, who is concerned this could degrade the plant control system's response time by facilitating random queries. RTAP/Plus controls the information that's extracted from the plant control system and passed to Oracle. Storing that information on Oracle makes it, in effect, another RTU to write to or read from. tesserNet developed an Oracle scan-task to pull only the desired data from the RTAP/Plus database, at the specified frequency, and download it to the specified Oracle table. Users then interrogate the Oracle datastore rather than the real-time system.

In this way, Oracle offloads the burden of a heavy volume of user queries, and insulates the plant control system from the traffic. The point of control then resides with the manager of the RTAP system, who determines which queries get passed from the users to the real-time plant control system, and which ones can be handled by the Oracle system. Nonessential queries are screened out, or scheduled to run at less busy periods.

The Imperial project has proven that a carefully planned marriage of computers and networks can provide immediate as well as long-term bottom line improvement in oil production.


Charles Sykes profiles advanced manufacturing applications from his base in Silicon Valley.