PRODUCTION • PROCESSING • HANDLING
Since there is no pump rod, the pump can be used even for horizontal or heavily deflected boreholes: the so-called Dog Leg Severity (DLS) is very high
PUMPSBOOST PRODUCTIVITY
Progressing cavity pumps with underground drives operate efficiently and reliably in an environmentally friendly way
A
n oil and gas producer has been operating oil fields south of Bremen in Germany. For historical reasons, various types
of pumps were used side by side. Te installed centrifugal submersible pumps, pumpjacks and progressing cavity pumps handle local conditions, such as partially deflected boreholes, paraffin mixtures and sand mixtures, with varying degrees of effectiveness. In an effort to reduce the number of pumping installations, the oil field operator began to look for an efficient and durable system capable of combining the advantages of both: a system that combines the submersible motor of a submersible centrifugal pump with a progressing cavity pump. Te company decided in favour of a solution developed by Netzsch Pumps & Systems, based in Germany. Te ESPCP is a progressive cavity pump (PCP) system with submersible drive
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and a permanent magnet motor (PMM). Even with the difficult media described above, it allows higher flow rates than the previously used units. It even lowers operating costs thanks to its lower failure rate. Te main parts defining the conveying principle of the progressing cavity pump are a “rotating rotor” and a “fixed stator” in which the rotor turns. Conveying chambers between both parts continuously move from the intake to the outlet side and transport the medium. With this principle, consistency and viscosity of the medium are not relevant to the flow.
BETTER HANDLING Te ESPCP used by the customer has a special rotor connection, and is driven from inside the borehole. Te special feature of this pump is that the motor and the bearing unit are connected directly to the rotor via a flexible rod. All radial and
axial forces of the rotor are absorbed by a special underground bearing housing. Tere is also a dynamic seal in the well. Tis moved all critical components of the pumping unit below ground, precluding environmental impact from leaks above ground. Te motor that has been selected for the system is a permanent magnet model (PMM). It is designed to meet the specific requirements of a progressing cavity pump. “Tanks to the permanent magnet motor, the pumps can be installed deeper. Tey can also be used if there is a high deflection,” says Jörg Eitler, head of business field Oil & Gas Upstream.
ADVANTAGES COMPARED TO PCP MODELS WITH ABOVE- GROUND DRIVE
Te design of the ESPCP system is adapted to local conditions: it conveys the highly viscous medium, which contains bitumen and paraffin sediments, sand content of up to 40%, or salt deposits, at a pressure of up to 300 bar. A gas proportion of up to 40% of the pump intake does not pose a problem during extraction, because the technology of the progressing cavity pump allows conveyance of different phases of a fluid. It also conveys low volumes of 3 to 20m³/ day as efficiently as medium volumes of 10 to 100m³/day. Te pump can be used even for horizontal or heavily deflected boreholes.
In November 2018, a Netzsch ESPCP system was installed in the oil field of a German oil and gas producer. The photo shows the well, which was converted from a decommissioned pumpjack (right) to the rodless PCP (left)
Jörg Eitler is with Netzsch
www.netzsch.com
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