Progressing Cavity Pump (PCP) systems are generally the preferred method for lifting cold viscous, sand laden fluids. PCP’s are a positive displacement pump with a helical metal rotor which rotates in an elastomeric stator. The elastomeric stator is attached to metal tubing.  In its most basic form, the rotor has a single helical shape and the stator has a double helical shape. The eccentric motion of the rotor turning inside the stator provides a series of sealed cavities between the stator and rotor. The close fit of the rotor and the viscosity of the fluid help to provide a seal. The fluid progresses from the intake to the pump discharge, which is connected to production tubing. The pump displacement rate is proportional to the rotational speed of the rotor and the differential pressure across the pump. PCP’s are usually driven by “top-drive” systems attached to the top of the wellhead, using hydraulic or electric power to turn the rod string.

 Bottom-drive systems using modified Electric Submersible Pump (ESP) components have also been developed to drive the PCP system, thus eliminating the rod string and problems associated with top-drive systems in highly deviated wells. In some cases bottom drive systems enable higher production rates than top-drive systems.

 Since their invention in the late 1920’s, PCP’s have been widely used in the food industry for pumping thick fluids such as chocolate and peanut butter. Their geometry and resistance to abrasion is well suited for efficient pumping of viscous and sand-laden fluids. They have been used to assist heavy oil production since the 1970’s. Top-drive PCP systems are the preferred lift method of choice for operations involving the Cold Heavy Oil Production with Sand (CHOPS) recovery method.

 PCP systems deliver a relatively constant “smooth” flow, avoiding excessive shear stress that could encourage emulsification.

 There are many choices of elastomer use in PCP application. Current elastomer temperature limits restricts their use to about 325 degF (163 degC). This http://www.spe.org/specma/binary/files/519251697796Syn.pdf May 2006 JPT Online article describes the development of an all metal pump designed to withstand higher temperatures 

 Jet Pump systems have been deployed for cold heavy oil production. Water or lighter oil is used as the power fluid.

 Hydraulic Gas Pump (HGP) systems have been used, typically for temperatures lower than 200 degC (390 degF). High-pressure gas is pumped from the surface then injected at high pressure to positively displace and lighten the weight of production fluids.  

 Gas Lift is often used to improve production of fluids with a viscosity in the range of 10 – 20 cP. This incurs the cost of a natural gas supply, recycling equipment, pumping and compression systems. In addition, high shear stresses from injection can lead to emulsification in the produced fluids. Sophisticated gas lift systems are rarely combined with thermal recovery methods because suitable packers, mandrils and valves quickly become unavailable with increasing temperature.

 “Poor boy gas lift” is used in some high temperature applications. This involves gas being pumped downhole through a pipe, typically a length of coiled tubing, opening directly into the production stream. In addition to the additional costs and risk of emulsification, this poorly controlled system can deliver very variable production rates. An additional downside is that the injected gas cools the production stream, working against the expensive heating effort. 

Read about other artificial lift systems for heavy oil.