Abstract
The application of Progressing Cavity Pumps ("PCP's") for artificial lift is still new compared to other technologies. The technology is advancing rapidly and that, combined with new techniques which are learned empirically, continually expands the range of applications. Continuous review is necessary to stay abreast of the technology. This paper discusses the state of the art and the directions in which it is going.
Increasing the range of application of PCP's is mainly dependant upon the advancement of elastomer technology. A review of the elastomers now being used or tested, their application and how they are made, is presented.
Rotor life is often the determining factor in PCP life. PCP suppliers are doing novel work in plating and hardening of rotors. Some of this work is described.
As the displacements of PCP's increased and they were used at greater depths, the increasing torsion on the drive strings created a serious safety hazard and the drivehead designs became increasingly inadequate for the larger loads. The status of the work to create a set of standards which can be incorporated into safety legislation, and upon which petroleum engineers can rely to select driveheads for safety and reliability, is described. This includes the design criteria which must be considered in the selection of a drivehead.
The status of the work on ISO norms is also reviewed.
Two novel applications for wellbore PCP's are revealed. The conclusions and recommendations summarize the applications and limitations of PCP's for artificial lift.
Introduction
The PCP is a type of spiral gear pump. The principle of the PCP was disclosed by Mr. Rene Moineau. Oil well PCP's are very simple pumps consisting of only 2 parts; the stator which is usually attached to the end of the tubing, and the rotor which is usually attached to the end of a sucker rod string. In this case, the pump is powered by rotation of the sucker rod string. The principal and the geometry of the PCP which make it the best sludge pump and particularly suitable for the pumping of deep wells, have been described in previous papers.
PCP's first found wide application in Canada, for pumping sand-laden heavy oil. The capital cost and operating cost advantages led to the application of PCP's for artificial lift of medium crude, usually with high volumes of water. This required the development of high volume pumps with elastomers which resist aromatic solvents and H2S. PCP's with high head rating were first developed for pumping high viscosity crude oils, but can also be used to lift low viscosity crude from deeper wells. This has lead to the requirement for pumps which resist high temperatures and the high aromatic solvent contents of some light oils. Steam flood applications also introduce the requirement for high temperature resistance.
PCP's have also been used extensively in the USA for the dewatering of methane coal-bed wells, although they have been phased out in most fields in favour of small pump jacks as the water production declined.
