New Developments

Metal-to-Metal Pumps

Metal stators were considered years ago, but only recently have newer manufacturing techniques and the application of metal-to-metal PCPs in thermal heavy oil and bitumen recovery applications, such as steam assisted gravity drainage (SAGD) and cyclic steam stimulation (CSS), brought this technology to the forefront. A metal stator does not have many of the shortcomings of elastomeric stators--specifically fluid interactions and temperature limitations. Metal stators may therefore be used in thermal applications (e.g. 160-350oC), or applications with highly reactive fluids. Potential problems which are actively being resolved by metal-to-metal PCP vendors include vibration and sealability with low viscosity fluids, the latter due to the fact that metal-to-metal PCPs have a gap between the rotor and stator and not an interference fit, as normally exists with an elastomeric stator.

High Temperature Elastomers

One of the major limitations of elastomeric stators is the temperature. At high temperatures and over time, most elastomers, including the nitriles typically used in PCPs, become hard and brittle and may not form a seal with the rotor. In these conditions, pumps can fail very quickly. High temperatures can be caused by the external conditions in the well (from depth, or from thermal operations), or from internal friction between the rotor and stator in the absence of sufficient cooling. Fluorocarbon elastomers can operate at higher temperatures than nitriles, but at the cost of inferior mechanical properties. Research is ongoing into ways of improving elastomer formulations for PC pumps so that continued operation at higher temperatures is possible.

Fluidizing Sand

PC pumps are capable of producing large quantities of sand, when the sand flows into the well on a continuous basis. Sand is known to enter the wellbore in slugs, however, and these slugs can overwhelm the pumps' capabilities of producing solids, particularly in applications where sand control is not employed (eg. in producing viscous heavy oil from unconsolidated sandstone reservoirs). Various methods of "fluidizing" sand to ensure that it can be produced through the pump have been used, and others are in development. Some methods are: the addition of a "paddle" rotor extending below the intake to continually agitate the fluid entering the pump; a hollow rotor feeding a small portion of produced fluid from the pump discharge to a jet located at the intake; and a fluidizer pump, where a large displacement-low pressure pump is installed below the main pump with holes in the tubing joint between the two so that an excess amount of fluid continually circulates in the annulus of the well and through the pump intake.

High Speed Pumps

Currently most PCPs are run at speeds below 500 RPM - with viscous oils, the limit is normally even much lower. To produce larger volumes without exceeding these speed limits, higher displacement pumps are needed. Higher displacement pumps are larger in diameter and/or length, have higher torque requirements, and normally result in increased axial load in the rod string. Being able to run smaller pumps at higher speeds (i.e. in excess of 500 RPM) reduces these loading effects, and also opens up "insertable" pumps (where the rotor and stator are run together on the rod string) to a larger range of applications