**3.3.1 Pumps**

It was necessary to install down-hole production pumps because the artesian production was not sufficient. Thus, two types of production pumps were deployed in the production wells: a Line Shaft Pump (LSP; in GPK2) and a Electro-Submersible Pump (ESP; in GPK4).

The LSP itself is in the well while the motor is at surface. The connection is obtained through a line shaft. The main advantage is to avoid installing the motor in hot brine, but the possible installation depth is limited and the line shaft has to be perfectly aligned. The LSP was supplied by Icelandic Geothermal Engineering Ltd. The length of the shaft is 345 m. The shaft (40 mm diameter) is put in an enclosing tube (3" internal diameter) with bearings every 1.5 m. The enclosing tube is set by means of centralisers in the middle of the LSP production column (6" internal diameter) which is put into the 8" casing. The pump itself is from Floway (USA) and made of 17 different stages of 20 cm (3.4 m total length). The LSP flow rate can be modulated until 40l/s with a Variable Speed Drive. The maximum rotation speed is 3000 rpm at 50 Hz. The surface motor is vertical. Metallurgy is cast iron and injection of corrosion inhibitor can be done at the pump intake by mean of coiled tubing. Shaft lubrication is made with fresh water injected from surface in the enclosing tube. The pump has been installed at 350 m depth into GPK2 that presents good verticality and is the best producer. Due to hydraulic drawdown, the maximum flow rate expected with the LSP installed at 350 m is 35 l/s. During summer 2008, (07th July to 17th August), after six weeks of geothermal production (25 l/s, 155°C), scaling problems were observed within the lubrication part of the shaft. The fresh water used for lubricating the shaft was too mineralized and some carbonate deposits (calcite, aragonite) precipitated. Then, a poor lubrication occurred and the first axis of the shaft broke. Between mid August and November 2008, both the shaft and the pump were fully dismantled, analyzed and a demineralization water system was set up. The LSP pump was re-installed at 250 m depth in GPK2 and worked properly afterwards.

Both the ESP pump and its motor are installed into the GPK4 well at 500 m depth. The maximum expected flow rate from GPK4 equipped with ESP is 25 l/s but the pump is designed to a maximum flow rate of 40 l/s. The ESP was delivered by Reda/Schlumberger. Due to the expected maximum temperature (185°C) and the salty composition of the brine, specific design and noble metallurgy had to be used. The electrical motor is beneath the pump and connected to it through a seal section that compensates oil expansion and metallic dilatation. The motor is cooled by the pumped geothermal brine and internal oil temperature can reach 260°C. A fiber optic cable has been deployed with the ESP and allows monitoring the motor temperature and gives downhole information about the geothermal draw-down in the well. The first production tests from GPK4 with the ESP with an expected target of 25 l/s started on mid November 2008. After some days of production, GPK4 production decreased to 12.5 l/s at 152°C and the geothermal water was re-injected in GPK3 at 50°C. GPK2 flow rate was stabilized at 17.5 l/s for a temperature around 158°C. Both flows coming from GPK2 and GPK4 were re-injected under full automatism in GPK3 at 30 l/s. The ORC commissioning started for these geothermal conditions at around 155°C. GPK3 well-head pressure was maintained around 70-80 bars for reinjection.
