Objective
To test a new type of turbo-pump for a production well in Dogger as part of a larger geothermal programme comprised of four pairs of wells for district heating in the town of Meaux in France. This is a prototype geothermal extraction pump, developed by Ets Pompes Guinard and it consists of a pump part plus a turbine part integrated in one single submerged unit., free of any electric equipment (cable and/or motors). This type of pump is particularly suited to a high temperature (+ 70deg C) and/or corrosive geothermal waters and to well pumping depths over 200 m. It constitutes a valid alternative to the electric pump with submerged motor and the vertical long shaft pump.
New technology incorporated in the prototype will provide a more reliable cycle pump, with a longer life and reduced maintenance and replacement costs. It can also readily accommodate variations in flow rates and is easily installed and removed.
The 500 KW nominal power turbo-pump was installed at 250 m yielding a maximum production rate of 265 m3/h at 78 C and 25 g/l salinity. The entire pumping unit Guinard of Meaux-Beauval 2, corresponds closely to manufacturer's specification and has produced satisfactory results. The functioning of the installation has proved to be quite good, although some technical problems, frequency variator, bearings, packing leaks had reduced the utilisation of the entire system.
Pumps of this type can operate in conditions of up to 250 C, salinity of 150 g/l, 300 m3/h flow-rate, and a depth of 500 m (for a double stage pump). In such circumstances the turbo-pump compares very favourably with the various traditional pumps, particularly with regard to reliability, ease of access to sensitive parts in case of repair. These advantages outweigh the lower efficiency of between 35 and 45% in comparison with 65% for an electric pump with a submerged motor, and the high initial investment and operational costs.
With many geothermal projects operating in difficult physical/chemical environments, it is clear that a market for pump equipment of this type exists. Potential for replication is promising and in the event of industrial scale mass production for satisfying the European and the world geothermal market, a considerable cost reduction of up to 50% is expected. Guinard has developed a second generation of turbo pumps, and up to now eight of these pumps are already installed in existing geothermal wells to exploit the Dogger aquifer.
The turbo-pump is running since 1984 and would be removed in 1993 for production well recovery and the installation of a downhole inhibitor pipe. The duration life of the system (9 years) is 3 times longer compared with comventional electrical submersible pumps.
The operating principle of the pilot unit is the following: the complete pumping unit - at fixed or variable speed - consists of a turbo-pump in the borehole with a second surface booster pump (multi-stage high pressure pump) to drive the hydraulic turbine. The submerged pump located in the well pumping room is driven by the turbine only and, therefore, needs no electric cables or motors. The complete assembly, single stage pump plus turbine (comprising 5 stages, 2 hydraulic radial bearings, 1 hydrostatic axial thrust bearing and 1 balancing piston), is integrated in a single submersible pump/turbine unit known as turbopress (the patent brand name).
Pump and turbine are commonly mounted on a common high speed shaft (6 000/7 000 revs/min). The turbine comportment uses the same effluent as the pump, which is pressurised by the surface booster and filtered by a surface unit. After driving the turbine, the effluent passes up the column pipe and at the surface divided into two parts, the turbine capacity Qt and the pump capacity Qp. The turbo-pump trials are being conducted at the Meaux-Beauval 2 GMX7 production well. The manufacturer, Etablissements Pompes Guinard have previously, tested the equipment in their plants, while a pilote unit of this pump was built and tested by SNEAP/DIENIC. The project at Meaux is the largest geothermal operation in France and consists of four pairs of wells (four production and four reinjection) drilled down to a depth of approximately 2 000 m.
The Dogger reservoir which extends from 1 790 m to 1 915 m has the following characteristics: temperature: 78 c, average salinity: 35 g/l, total flow-rate (all four production wells): 1 150 m3/h. Surface installations include three geothermal plants connected with 3 back-up heating plants peak hour operation, 4 geothermal pumping stations, 3 district heating networks and 123 sub-stations. The geothermal energy covers almost 80% of space heating and hot water requirements for some 15 000 dwellings-equivalent (council and private dwelling houses, 1 hospital, several schools and some other public buildings). The geothermal scheme has been operating since october 1983 and has given energy savings of 19 800 tonnes of oil equivalent per annum (TOE/year). Investment for the geothermal programme totalled to 297 Millions FF including 4.3 Millions FF for the turbo-pump project described above.
Topic(s)
Call for proposal
Data not availableFunding Scheme
DEM - Demonstration contractsCoordinator
77100 Meaux
France