Ingeborg Kleinfeld explains how an underground driven progressing cavity pump was configured for changing pumping conditions and a high free gas content
To optimise the efficiency of oil production on the Bramberge oil field in the German Emsland region, the management at Neptune Energy decided to choose a progressing cavity pump with underground drive – an electric submersible PCP system – from Netzsch Pumps & Systems, which can be configured for low flow rates and a high free gas content. The solution is based on the rotor-stator principle and features an efficient permanent magnet motor. Changing pumping conditions can be adapted, even when installed. The installed downhole sensor system allows the pump to continuously supply application information from the well.
“Our challenge was to offer a technical solution that is equally reliable as the gas lift process but highly flexible at the same time,” explains Jörg Eitler, Head of Oil & Gas Upstream at Netzsch. “It should be possible to adapt the system to the changing conditions – even when installed directly in the well.” In addition, the operating company also needed reliable pressure and temperature data from a depth of around 1,000m in the well. Based on this requirements profile, Netzsch suggested an ESPCP system with a downhole sensor system.
A progressing cavity pump with high flexibility
The site in the German Emsland region uses the ESPCP – a progressing cavity pump with underground drive. “The special feature of this pump is that the rotor and the motor are sunk into the well. The motor and the bearing unit are connected directly to the rotor with a flexible rod. All radial and axial forces of the rotor are absorbed by a special underground bearing housing. In addition, the dynamic seal is also located in the well,” explains Eitler. This excludes environmental impact by leaks above ground.
The motor of the system is a permanent magnet mode (PMM) with a special control, which features a very high efficiency and covers a large speed range. This helps to ensure flexible flow rates. “This was necessary because the previous way of pumping the oil-water-gas mixture using gas lift meant that there was not much reliable data on the actual gas content,” the pump specialist continues. “During the initial phase, we even had to assume an extremely high gas content of over 90%.” Thanks to the PMM and the control precisely matched to the motor, the solution designed by Netzsch reliably varies the required speeds between 100 and 500rpm.
As there was no reliable information on the pump intake pressure (dynamic fluid level), a very high safety factor was specified for the pressure capacity of the pump (rotor–stator combination). In addition to this, the pump system was equipped with a full downhole sensor system. The data obtained can be used to draw conclusions about the dynamic level of the fluid in the borehole and they are important for the early detection of faults. The signals are sent to the surface through the existing power cable and used for the central controller.
The ESPCP pump system was commissioned in mid-November 2019. It has since been running to the full satisfaction of the oil field operator.
Ingeborg Kleinfeld is with Netzsch