A German energy supplier had initially used a geological horizon for gas storage, but then decided to extract crude oil from the same deposit. Therefore, a suitable extraction system had to be acquired for transporting the multi-phase mixture with a high gas content to the surface from 1,200 m below.
Due to the extreme conditions, a special pump technology was required: centrifugal pumps with submersible drive were not suitable due to the high risk of failure from gas lock, while the progressing cavity pumps with above-ground drive, as commonly used in Central Europe, posed the risk of a blowout on the surface. This prompted a detailed production and profitability analysis which showed that a conversion from gas to oil production for this bed was economically viable.
Extreme conditions
The extreme conditions on site, however, presented very high requirements for the pump design: as the medium was a multi-phase mixture with a very high gas content, the usual centrifugal pumps with underground drive were not an option.
With a very high free gas content, this type of pump always presents the risk of all impellers filling up with gas. Therefore, it was extremely likely that a centrifugal submersible pump would have failed in this application due to the so-called gas lock.
The progressing cavity pumps, which are normally used in Central Europe until now, have been systems with above-ground drive. These units have a dynamic seal on the surface which has a significant disadvantage in case of extreme pressure increase on the intake side: the seal can become overloaded and trigger a blowout.
Special feature
To exclude this risk, Netzsch decided on a progressing cavity pump which is driven underground with the Netzsch ESPCP. The special feature of this pump is that the rotor is not driven via a very long rod, but rather the rotor-stator combination and the motor are sunk into the well.
The motor is connected directly to the rotor via a short flexible rod. All radial and axial forces of the rotor are absorbed by a special underground bearing housing. In addition to this, the dynamic seal is also located in the 1,200 m deep well. This moved all critical components of the pumping solution below ground, precluding environmental impact from leaks above ground.
