Heavy Oil Science Centre - Overburden

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Completions and Workovers

Oil Production Systems

Reciprocating Pumps

Reciprocating pumps go back more than 2000 years. Modern improvements such as   closer tolerances have greatly improved efficiency. However, limitations remain (e.g. the stopping at each extreme of the stroke). As well, sand, may clog valves and wear parts.

"Horsehead" Pump jacks were once a mainstay of our prairie scenery. They convert rotational power, provided by an internal combustion or electric motor, to reciprocating power delivered to the downhole production pump through the "rocking horse" and a string of sucker rods.

Oil collects in a perforated nipple at the lower end of the pump. The plunger, which is attached to the sucker rod, moves up in the barrel forcing the upper check valve into its seat. This movement creates a vacuum in the pumping chamber unseating the lower check valve and drawing oil in. When the action reverses, pressure is created in the chamber when the lower check valve is seated as the plunger moves down. This pressure opens the upper check valve releasing the oil into the tubing and the action repeats. The stroke rate of the pump is set to suit the flow character of the well.

Progressing Cavity Pumps

Because of their tolerance to sand, Progressive Cavity (PCP) systems are becoming the choice in the Lloydminster region . These pumps can handle product that is in excess of 50% sand. PC pumps are more efficient than reciprocating pumps, have only one moving part and no valves, and are better suited to the production of slow flowing, high viscosity heavy oil. The system works best in shallow wells and lower temperatures, both conditions of our area.

The mechanism consists of a synthetic elastomer stator that is fixed within a pump barrel which is attached to the tubing and lowered into the reservoir. A helical steel rotor is turned, by a rod string from the surface (downhole drive technology is being developed), within the stator. At the suction end, an open cavity fills with product and, as the rotor turns this cavity is closed off. The full cavity then progresses along the axis of the pump to the discharge end. As the pump operates, cavities are continually made and transferred producing a relatively constant flow. The rpm of the rotor can be adjusted to suit the flow nature of the well.

Steam Assisted Gravity Drainage (SAG-D)

The Lloydminster region has enormous reserves of heavy oil which are too deep to mine and are difficult to extract by conventional methods. SAGD is an experimental process designed to enhance the extraction of viscous heavy oil from thick channel sandstone reservoirs. The SAG-D process is based on two, well known and basic, facts: that hot oil flows better than cold oil, and that gravity pulls the densest materials to the bottom.

The system involves the drilling of two or more wells into the pay zone of an oil bearing reservoir. A horizontal production well is drilled into the lower part of the reservoir, and horizontal or vertical steam injection wells are drilled above and close to the production well. Steam is injected into the reservoir, heating and improving the flow characteristics of oil which drains into the production well.

Sufficient steam injection is required to build a steam chamber that rises to the top of the reservoir, while hot oil drains down to the producing well.