This article, written by Technology Editor Dennis Denney, contains highlights of paper SPE 97796, "Development Status of a Metal Progressing Cavity Pump for Heavy-Oil and Hot-Production Wells," by J.-L. Beauquin and C. Boireau, Total E&P, and L. Lemay and L. Seince, PCM Pompes, prepared for the 2005 SPE International Thermal Operations and Heavy Oil Symposium, Calgary, 1–3 November.
Progressing cavity pumps (PCPs) often are used for cold heavy-oil production because of their adaptability to viscous and abrasive fluids. However, for thermal recovery, a standard PCP is not adaptable because the elastomer of the stator, the heart of the pump, cannot withstand fluid temperatures higher than 160°C. An all-metal pump, avoiding the elastomer weakness, has been developed. Validation tests began in early 2005 using extra heavy crude with temperatures up to 200°C, pressure up to 75 bar, and flow rates up to 260 m3/d at 350 rpm. The flow-rate range will be as high as 1000 m3/d.
Most oil fields require some type of artificial lift at some point in time. When sufficient gas is available, gas lift may be a viable lift method because it involves relatively low-cost well interventions and tolerates numerous flow constraints, such as high gas content, gas slugging, sand production, and high temperature.
When a gas lift system is inadequate, too expensive, or not possible, the artificial-lift needs challenge downhole pump capabilities and features. Some wells are able to use hydrodynamic pumps such as centrifugal, helicoaxial, or hydraulic-jet pumps because of the very high volume to be lifted. However, these pumping technologies are expensive. Most pumped wells are equipped with positive-displacement pumps, which can be adapted to changing conditions of pumped fluid.
Beam- and rod-driven plunger pumps can be adapted to handle many types of fluids because they are simple, robust, and well understood. However, in heavy oil, rod failure is the most common limitation, which leads to limiting the well production, which, in turn, worsens the risk of sand settling in the pump. Also, slow closure of traveling and standing valves is a cause of poor efficiency in viscous mixtures.
Pumping in horizontal or highly deviated wells also limits the plunger downstroke because it is powered by the driving part of the rod-string weight. Thermal production methods generate fluctuating inflow properties that change rod-failure causes and reduce the run life of the system.
During the 1980s, rotating-rod-driven PCPs were developed for oilfield applications. PCPs are used for viscous oil, horizontal wells, and sandy production. Rod-driven PCPs are used for cold pro-duction of heavy oil and often are used in conventional mature fields as a cheaper lift method than beam pumps. The standard PCP stator is made of elastomer, which is the source of most of the pump's limitations including fluid temperature and gas and aromatics content.