Wellhead Monitoring and Control

As more and more of the world’s known oil reserves are depleted, new sources are constantly being sought out.  But finding a new source of oil is just the beginning.  Sometimes, getting that oil out of the ground demands developing new technologies. The CMX™ Process Control System is playing an integral part in an exciting Canadian enterprise that is presently bringing in over 100,000 barrels a day.

It began in early in the Autumn of 1983 when the Alberta Energy Resources Conservation Board of Canada approved a plan that proposed to exploit the oil-rich sand deposits near Cold Lake, Alberta.  Here, a sandy tar-like substance called "bitumen" is found in a 50 meter thick layer approximately 450 meters underground. With the room temperature consistency of cold molasses, bitumen can’t be pumped to the surface.  Because of its depth, surface mining is not practical.  To extract the bitumen, a new recovery method known as "cyclic-steam stimulation" had to be developed.

Informally known as “huff and puff,” the cyclic-steam stimulation method heats and thins the bitumen by injecting steam heated to 300 degrees Celsius under 11,000 kilopascals of pressure into the well bores. Periods of steaming usually lasting four to six weeks are followed by periods of “soaking” lasting four to eight weeks.  Production periods follow in which the bitumen is pumped to the surface.  The duration of successive steam-soak and production cycles increases over time taking up to two years to complete as more distant reservoirs are depleted.

After the heated bitumen and water is pumped to the surface, it is piped to a central plant where the water is separated from the bitumen, cleaned up, and recycled back into the steam boilers. The bitumen is blended with a light hydrocarbon diluent made up of natural gas condensate so that it can be shipped to market by pipeline.

Today, there are more than 3000 producing wells at Cold Lake covering 780 square kilometers of oil sands.  To minimize the environmental impact while providing access to the largest area of the underground oil-sands formation, the individual wells are clustered in surface “satellite pads” of 20 or 30 wells each.  Over 140  CMX™ Systems are currently monitoring and controlling wellhead operations at various satellite pads.  Twelve Sequence Control Language (SCL) programs, 20 primary/cascaded control loops, and 256 digital and 120 analog I/O points on each  CMX™ System monitor and  control wellhead operations, temperatures, pressure, and flow as well as metering and gas-recovery equipment via their associated Reliance AutoMate and Modicon 984/Quantum PLCs.  Each  CMX™ System communicates with a central Honeywell TDC3000 computer for data display, data acquisition and long term historization, and for production reports and process optimization.

Cold Lake bitumen contains a high concentration of hydrocarbon elements called “asphalhatenes” which makes it highly suitable for manufacturing asphalt.  More complex refining is needed to upgrade it into lighter hydrocarbon products such as gasoline or diesel fuel.

About 65 percent of the Cold Lake product is shipped east through the Interprovincial Pipeline to markets in Ontario and the U.S. Midwest. The major refining centers in Chicago and the Midwest states area account for about 80 percent of consumption in that area, while Ontario refiners account for the rest.  Another 35 percent is used by major prairie customers in Edmonton, Bi-provincial upgrader at Lloydminster and refineries in Montana. 

Extensive effort has been put into safeguarding the environment during development at Cold Lake.  While the need for miles of pipelines, hundreds of wells, and large steam generation plants is bound to have some effect on the environment, methods have been developed to keep any impact minimal.  Cluster drilling, shared rights-of-way, emission controls and maximum water reuse are a few of the proven techniques being employed to ensure that development minimizes environmental disturbance.  As development areas are abandoned they are being reclaimed, re-establishing a landscape similar to that now found surrounding the project area.

As the production of light, sweet crude oil in North America continues to decline, it is expected that demand for heavy oil products like Cold Lake’s blend will continue to grow to just under 900,000 barrels a day by the year 2000.  The  CMX™ Process Control System will be there continuing to do its part in supplying heavy oil to refineries both in Canada and the U.S.