The Progressing Cavity pumps (PCP) have been utilized for fluid transfer in various industrial applications and surface transfer of oilfield fluids for many years. Over the years, extensive research and development has been conducted in the design of progressing cavity pumps. This has expanded their production and lift capabilities, making them suitable for various applications. With different elastomeric materials, these pumps can efficiently handle multiple well fluids. The progressing cavity pump is an excellent option for wells that use artificial lift and contain thick, sand-laden crude oil. The pump can handle abrasive fluids, lift up to 6000 feet, and has a capacity of 3000 barrels per day. Due to its efficiency, it is popular as an alternative pumping solution for oil wells.
The versatility and functionality associated with PCP applications have caused new products and equipment designs. Over time, PCP technology has evolved into bottom-driven PCPs using an electric submersible motor called an ESPCP (Electrical Submersible Progressing Cavity Pump). The combination of PCP and ESP technology has eliminated the need for sucker rods, thus expanding the application range to deviated and horizontal wells where traditional rod-driven PCPs have limitations. The use of standard induction motor technology required a speed reduction from the synchronous speed of the ESP motor to that of the PCP (typically in the range of 100 - 500 rpm). To accomplish this, a downhole gear reducer accommodates the speed requirement discrepancy between standard ESP and standard PCP operating speeds. The downhole ESPCP gear reducer is an expensive component and is one of the most likely failures sites in the system. However, the introduction of permanent magnet motors (PMMs) has eliminated the need for a gear reducer by providing a direct speed ratio. This greatly simplifies the ESPCP string for increased flexibility and improved reliability.
The PCP pump has its advantages but also has some limitations and requires special considerations. Since the pump is made of thick elastomeric material that is a strong thermal insulator, and as a result the environmental temperature cannot exceed 85°C (185°F). The dynamic loading of the elastomer builds heat and causes interal heat rise called hysteresis which can cause the elastomer to exceed the environmental temperature by upwards of 30+°C and ultimately prematurely fail. Additionally, the elastomer is susceptable to thermal swell from its high coefficient of thermal expansion and chemical attack and swell from the elastomer's natural effinity to many oils. This swell means higher temperature and light oil pose challenges to dimensional stability of the elastomer. When combined, light oil and higher temperature cause significant dimensional changes in the elastomer; distorting the designed shape and ultimately causing rotor interference issues which mechically damage the pump. Consequently, PCPs have been limited in application for warm wells with light oil (high API) which are typically the types of wells seen in the unconventional markets that need a pumping solution.
